ANALYSIS SYSTEM FOR DETERMINING IONS IN AN ION-CONTAINING LIQUID MEDIUM AND ANALYSIS METHOD

Description

[0001] The present invention relates to an analytical system for the qualitative and / or quantitative determination of ions in an ion-containing liquid medium. The present invention also relates to an analytical method carried out with said analytical system.

[0002] To determine ionic parameters in aqueous solution and to monitor them automatically using probes, ion-selective probes are frequently used today. These probes can each determine a single ionic parameter via its redox potential in the solution. Ion selectivity is achieved through the use of ion-selective membranes.

[0003] In practice, however, these probes exhibit some serious disadvantages. For example, the electrodes show cross-sensitivity. This means that the electrodes generally do not have complete selectivity and therefore also measure interfering ions, which distorts the measurement results. Another problem is the high sensitivity of the membranes used to environmental influences. Furthermore, ion-selective probes are expensive, which makes them inaccessible to certain users (e.g., private individuals). Finally, such probes require regular recalibration, which leads to high maintenance costs, especially with continuous use.

[0004] The increasing pollution of waterways is a global problem and is also very prevalent in technologically advanced countries of the developed world. One cause of this problem is the progressive industrialization and commercialization of the agricultural sector. To meet global food demands, agriculture must produce ever more food on ever smaller areas. This is further complicated by the increasing demand for biomass for climate-neutral energy production. To meet this demand, agriculture must rely on artificial fertilizers, which keep the soil fertile even under very high levels of use. Furthermore, the use of fertilizers increases crop growth and thus the overall yield.However, the fertilizers used are not completely absorbed by the crops, and the excess fertilizer is washed into the surrounding waters and groundwater by rain, which can have serious consequences for the ecosystems found there.

[0005] An excessive presence of plant nutrients leads to increased algal growth. Dead algae sink to the bottom of the water body and are usually broken down there through aerobic decomposition processes. If excessive algal growth occurs, more algae die, and more oxygen is required to decompose this biomass. This, in turn, can be fatal for other aquatic organisms, such as fish, and can trigger mass fish kills. If, over time, no oxygen remains in the water, the biomass decomposition occurs anaerobically, i.e., without oxygen. This also results in the formation of harmful gases and is colloquially referred to as the "turning over" of the water body.

[0006] Over-fertilization is not only harmful to the affected ecosystems, but can also directly harm humans. The nitrogen contained in fertilizers can leach into groundwater as nitrate and from there into our drinking water. Once converted into nitrite in our bodies, the nitrate can, in turn, cause health problems.

[0007] To prevent over-fertilization, continuous monitoring of water bodies is essential. This would allow for the optimization of fertilization itself, as well as a rapid response to excessively high fertilizer concentrations. However, current methods are not suitable for automated, large-scale water monitoring. Furthermore, it is desirable to monitor fertilizer concentrations in real time and to regulate fertilizer application fully automatically. However, current automated measuring systems and methods are too expensive, maintenance-intensive, and prone to malfunctions for such applications.

[0008] Furthermore, monitoring ion concentrations and identifying specific ion species in liquid systems is also of interest in other fields of application, such as water treatment plants, sewage treatment plants, industrial plants, etc. Another relevant application area for monitoring ion concentrations is aquariums, i.e., the qualitative and / or quantitative determination of ions in ion-containing liquid media used in aquariums. Aquariums often house plant and animal species (fish, small animals, etc.) that are sensitive to certain environmental conditions (e.g., the ion concentration in the aquarium water). A reliable and easy-to-use method for monitoring the qualitative and quantitative ion species present is therefore of great interest.

[0009] The object of the invention is therefore the development of an analytical system and an analytical method for determining ions in an ion-containing liquid medium, thereby overcoming the disadvantages of the analytical systems and methods used in the prior art. The analytical system and method proposed according to the invention should be more cost-effective to manufacture and operate compared to systems known from the prior art. Furthermore, the analytical system and method should be less sensitive to interfering ions and require less maintenance. In addition, the analytical system and method should be easy to handle. An electrochemical analytical system for ion-containing liquids is known from Japanese patent JPS579864 A.

[0010] To solve this problem, an analysis system with the features of claim 1 and an analysis method with the features of claim 13 are proposed.

[0011] As already mentioned, the present invention relates to an analysis system for determining ions in an ion-containing liquid medium.

[0012] An ion-containing liquid medium can be understood as matter in a liquid state that may contain ions. The liquid ion-containing medium can, for example, be an ion-containing liquid, such as a liquid solution. An ion-containing liquid solution can be understood as a homogeneous mixture comprising ions of at least one type dissolved in a solvent. The solvent can be, for example, water, and the solution accordingly an aqueous solution. The ion-containing liquid medium to be examined can, for example, be a sample taken from a static or flowing body of water, such as a lake or a river. Likewise, the ion-containing liquid medium to be examined can originate from a static or flowing reservoir of a wastewater treatment plant, a water purification plant, an aquarium, or an industrial plant.

[0013] Ions can be understood as electrically charged particles that arise from uncharged atoms or molecules through the loss or gain of electrons. Cations can be understood as positively charged ions that arise from uncharged atoms or molecules through the loss of electrons. Anions, on the other hand, can be understood as negatively charged ions that arise from uncharged atoms or molecules through the gain of electrons. Anions and cations can be monovalent or polyvalent.

[0014] The determination of ions is generally carried out qualitatively and / or quantitatively. Thus, the determination of ions can be both qualitative and quantitative. Alternatively, the determination of ions can be purely quantitative or purely qualitative. In the context of this disclosure, a "quantitative" determination is understood to mean a determination of a specific amount, for example, a quantity (also amount of substance) per volume, an absolute quantity (also amount of substance, mass, or the like), a relative quantity in relation to a comparative measure, or the like. A "qualitative" determination, on the other hand, is understood to mean a classification according to the type of ion, for example, regarding whether a specific type of ion is present or not.

[0015] The proposed analysis system for determining the ions present in the ion-containing liquid medium comprises a measuring cell and a measuring arrangement.

[0016] The measuring cell of the analysis system comprises a first measuring chamber, a second measuring chamber, and a sample chamber located between the first and second measuring chambers, which is designed to hold the ion-containing liquid medium. A first electrode is located in the first measuring chamber and a second electrode is located in the second measuring chamber.

[0017] An electrode can be understood as any electrical conductor in the form of a solid that is capable of conducting electrical charge carriers. "Conducting" in this context refers to the transport of electrical charge carriers, such as electrons or ions. Electrons can be understood as electrically charged elementary particles that carry a negative charge. The electrode can be made of a conductive material, for example, graphite, or a metal such as titanium or platinum. At an electrode, electrical charge carriers can transfer from the solid material from which the electrode is made to the surrounding medium, or electrical charge carriers can be absorbed from said medium.

[0018] A voltage can be applied between the first and second electrodes such that the first electrode becomes positively polarized (charged) and the second electrode negatively polarized, causing anions to be transported towards the first electrode and cations towards the second electrode. This "transport" of ions can, for example, refer to ion transport in a liquid medium.

[0019] In principle, any electrical voltage source designed to generate a voltage between two electrodes can be used to create an electrical voltage between the first and second electrodes. An electrical voltage source can be understood as an active two-terminal device that generates an electrical voltage between its terminals. A two-terminal device can be an electrical component or circuit with two connections (terminals, poles). The electrical voltage source could, for example, be a battery or a generator. To generate a voltage between the first and second electrodes, the electrical voltage source can be connected to the first electrode via a first electrical conductor and to the second electrode via a second electrical conductor.Depending on the electrical polarity between the first and second electrodes, there can be either a deficiency or an excess of electrons at the first or second electrode, respectively. The electrode can therefore be positively or negatively polarized.

[0020] In addition, an anion-selective membrane is arranged between the first measuring chamber and the sample chamber, which is designed to allow the passage of anions from the sample chamber into the first measuring chamber.

[0021] Furthermore, a cation-selective membrane is arranged between the second measuring chamber and the sample chamber, which is designed to allow cations to pass from the sample chamber into the second measuring chamber.

[0022] The first measuring chamber is filled with a first liquid measuring medium. This liquid medium may contain a first detection agent to form anion-detection agent associations when anions pass into the first measuring chamber. The second measuring chamber is filled with a second liquid measuring medium. This second liquid measuring medium may contain a second detection agent to form cation-detection agent associations when cations pass into the second measuring chamber.

[0023] In the context of the present invention, a liquid measuring chamber medium can be understood to mean any medium in a liquid state with which a measuring chamber can be filled. The first liquid measuring chamber medium can be understood as such a liquid measuring chamber medium with which the first measuring chamber is filled. The second liquid measuring chamber medium can, in turn, be understood as such a liquid measuring chamber medium with which the second measuring chamber is filled. Both the first and the second liquid measuring chamber medium can correspond to the ion-containing liquid medium. "Filling" can mean either a complete filling of the respective measuring chamber with the respective liquid measuring chamber medium or a partial filling (in which case the respective measuring chamber is not completely filled with liquid measuring chamber medium with respect to its volume).

[0024] The analysis system further comprises a measuring arrangement. The measuring arrangement is designed to photometrically measure the anions and / or anion-recognition compound associations present in the first measuring chamber, and / or the cations and / or cation-recognition compound associations present in the second measuring chamber. This can be understood in the sense of the following three alternatives.

[0025] In one alternative configuration, the anions and / or anion-recognition compound assemblies present in the first measuring chamber can be measured photometrically using the measuring setup. Thus, anions and anion-recognition compound assemblies can be measured photometrically. Alternatively, only anions or only anion-recognition compound assemblies can be measured photometrically. Based on the respective photometric measurement(s), the anions are then determined qualitatively and / or quantitatively. This can be understood as the determination of the anions being carried out both qualitatively and quantitatively. Alternatively, the determination of the anions can be carried out only quantitatively or only qualitatively.

[0026] Alternatively, the cations and / or cation-recognizant compounds present in the second measuring chamber can be measured photometrically using the measuring setup. This can be understood as the photometric measurement of cations and cation-recognizant compounds. Alternatively, only cations or only cation-recognizant compounds can be measured photometrically. Based on the respective photometric measurement(s), the cations are then determined qualitatively and / or quantitatively. This can be understood as the determination of the cations being carried out qualitatively and quantitatively. Alternatively, the determination of the cations can be carried out only quantitatively or only qualitatively.

[0027] Furthermore, the measuring setup can be used to measure both the anions and / or anion-recognition compound associations present in the first measuring chamber, and the cations and / or cation-recognition compound associations present in the second measuring chamber. Based on the respective photometric measurement(s), the anions and cations are then determined qualitatively and / or quantitatively. This can be understood as the determination of the anions and cations being carried out both qualitatively and quantitatively. Alternatively, the determination of the anions and cations can be carried out only quantitatively or only qualitatively.

[0028] The analysis system is advantageously universally applicable and adjustable. This means that the analysis system can be configured to measure anions and / or cations, quantitatively and / or qualitatively, in the first and / or second measuring chamber. Furthermore, the analysis system is advantageously relatively simple in design and easy to use, and therefore also suitable for use by an end user (layperson).

[0029] Furthermore, the analysis system is inexpensive to manufacture and maintain due to its simple design.

[0030] The dependent claims relate to advantageous embodiments and further developments of the present invention. The features mentioned in the dependent claims can be used in any combination to further develop the analysis system according to the invention, insofar as this is technically possible. This also applies if such combinations are not expressly clarified by corresponding cross-references in the claims. In particular, this also applies across the category boundaries of the patent claims, so that those features and / or embodiments described in the context of the analysis system can also be features and / or embodiments of the analysis method also proposed by the invention, and vice versa.

[0031] According to a first embodiment of the invention, a first mixing device and / or a second mixing device can be arranged in the first measuring chamber and / or in the second measuring chamber to mix the first and second liquid measuring chamber media contained in the first and second measuring chambers, respectively. This can be understood as follows: in a first alternative, a first mixing device is arranged in the first measuring chamber to mix the first liquid measuring chamber medium contained in the first measuring chamber, and a second mixing device is arranged in the second measuring chamber to mix the second liquid measuring chamber medium contained in the second measuring chamber. In a second alternative, a first mixing device is arranged only in the first measuring chamber. In a third alternative, a second mixing device is arranged only in the second measuring chamber.A mixing device can, in principle, be any device suitable for mixing the respective chamber media. The mixing device can be mechanical in nature (e.g., a stirrer, a magnetic stir bar with a magnetic stirrer), but it can also be based on flow or ultrasonic mixing. Any mixing or stirring devices known from the prior art can be considered a "mixing device" within the meaning of the present invention. Thorough mixing can improve measurement accuracy.

[0032] According to a further embodiment of the invention, the pH value of the first liquid measuring chamber medium contained in the first measuring chamber and / or the second liquid measuring chamber medium contained in the second measuring chamber can be adjusted. This can be understood to mean that the pH value of both the first liquid measuring chamber medium contained in the first measuring chamber and the second liquid measuring chamber medium contained in the second measuring chamber is adjusted. Alternatively, only the pH value of the first liquid measuring chamber medium contained in the first measuring chamber, or only the pH value of the second liquid measuring chamber medium contained in the second measuring chamber, can be adjusted.

[0033] Setting the pH value of the first liquid measuring chamber medium in the first measuring chamber and / or the second liquid measuring chamber medium in the second measuring chamber is important because the optional detection agents form the desired photometrically detectable ion-detection agent associations with the ions under investigation at specific pH values. For example, certain detection agents are only able to form these ion-detection agent associations with the ions under investigation at an alkaline pH value of the measuring chamber medium. Other detection agents, on the other hand, require an acidic pH value of the measuring chamber medium to form these ion-detection agent associations with the ions under investigation. The pH value of a medium can be understood as a measure of its acidic or basic character.The pH value can be the inverse of the base-10 logarithm of the hydrogen ion activity (i.e., the higher the concentration of hydrogen ions in a medium, the lower the pH value) and can take a value between 0 and 14. A pH < 7 corresponds to an acidic medium, a pH = 7 to a neutral medium, and a pH > 7 to an alkaline medium.

[0034] The pH of the first and second measuring chamber media can be adjusted by water electrolysis occurring at the electrodes, provided the measuring chamber media contain water. During water electrolysis, electrochemical processes convert water into hydrogen and oxygen, producing or consuming either hydronium ions (H₃O⁺) or hydroxide ions (OH⁻) depending on the conditions in the medium. For example, applying a voltage between two electrodes can produce hydrogen from water at a negatively charged electrode and oxygen at a positively charged electrode.

[0035] For example, when a voltage is applied between the first and second electrodes, thus positively polarizing the first electrode and negatively polarizing the second, a direct current can flow from the negatively charged second electrode to the positively charged first electrode during water electrolysis. This direct current flow can be understood as the migration of electrical charge carriers, such as electrons, via ions dissolved in the water. Due to electrochemical processes occurring during water electrolysis, the water in the second measuring chamber, where the negatively charged second electrode is located, can become alkaline and electron-rich (hydrogen-saturated), while the water in the first measuring chamber, where the positively charged first electrode is located, can become acidic and electron-poor (oxygen-saturated).

[0036] For example, water electrolysis can be carried out in such a way that an alkaline pH value is established in the second measuring chamber, in which the negatively charged electrode is located. The established alkaline pH value can promote the ability of a detection agent to form photometrically detectable ion-detection agent associations. For example, the ability of the metal indicator Calmagit (which can provide a detection agent) to form photometrically detectable cation-metal indicator complexes can be promoted by establishing an alkaline pH value in the second liquid measuring chamber medium, which contains Calmagit as the detection agent.

[0037] In principle, any water electrolysis setup designed to perform water electrolysis to adjust the pH of the first and second liquid measuring chamber media can be used. Three alternative water electrolysis setups are described below. However, it should be explicitly noted that these examples do not restrict the use to any specific water electrolysis setup.

[0038] As a first alternative, to adjust the pH of the first liquid medium in the first measuring chamber and the second liquid medium in the second measuring chamber, a charge-permeable membrane can be placed between the first and second measuring chambers to allow charge transfer between them. A charge-permeable membrane can be understood as any membrane that allows the passage of electrical charge carriers such as electrons, hydronium ions (H₃O⁺), or hydroxide ions (OH⁻). In principle, all known charge-permeable membranes can be used.

[0039] In a second alternative, a first charge-permeable membrane is arranged between the first measuring chamber and a first water electrolysis chamber equipped with a first water electrolysis electrode, in order to allow charge transfer between the first measuring chamber and the first water electrolysis chamber. In this case, a water electrolysis cell is formed from the first measuring chamber and the first water electrolysis chamber. The first water electrolysis electrode and the first electrode form a necessary water electrolysis cell electrode pair. The first electrode, in addition to the first water electrolysis electrode, forms another water electrolysis electrode of this water electrolysis cell. In this example, the first water electrolysis chamber and the first measuring cell are preferably filled with water.

[0040] Alternatively or additionally, a second charge-permeable membrane can be arranged between the second measuring chamber and a second water electrolysis chamber equipped with a second water electrolysis electrode, in order to allow charge transfer between the second measuring chamber and the second water electrolysis chamber. In this case, a water electrolysis cell is formed from the second measuring chamber and the second water electrolysis chamber. The second water electrolysis electrode and the second electrode form a necessary water electrolysis cell electrode pair. The second electrode, in addition to the second water electrolysis electrode, forms another water electrolysis electrode of this water electrolysis cell. In this example, the second water electrolysis chamber and the second measuring cell are preferably filled with water. For the operating principle of water electrolysis, please refer to the preceding explanations.

[0041] By adjusting the pH value based on the principle of water electrolysis, no electrochemical pre-amplification (applying a voltage to the first and second electrodes, resulting in ion migration and the subsequent formation of ion-recognizant compounds, if necessary) is required to bring the pH value into the range where the recognition compounds enable the formation of ion-recognizant compounds and their subsequent photometric detection. This is particularly advantageous for high ion concentrations in the liquid ion-containing medium. However, at low ion concentrations, electrochemical pre-amplification is advantageous to increase the respective ion concentrations in the measuring chambers or at the electrodes arranged in the measuring chambers, thus enabling a meaningful photometric measurement.

[0042] In a third alternative, the measuring cell for adjusting the pH value can have a pH adjustment chamber in the first and second measuring chambers. A first charge-permeable membrane is arranged between the first measuring chamber and the pH adjustment chamber, and a second charge-permeable membrane is arranged between the second measuring chamber and the pH adjustment chamber. In this context, a charge-permeable membrane can be understood as any membrane that allows the passage of electrical charge carriers such as electrons, hydronium ions (H₃O⁺), or hydroxide ions (OH⁻) through the membrane. Using this chamber arrangement and the first and second electrodes, the pH value can be adjusted by applying a voltage to these electrodes, thus performing water electrolysis.In this example, the first and second electrodes form a water electrolysis electrode pair necessary for carrying out water electrolysis. For the operating principle of water electrolysis, please refer to the preceding explanations.

[0043] Unlike water electrolysis, such a setup can also utilize an alternative pH adjustment method that takes advantage of the first and second electrodes. In this case, a different medium can be present in the pH adjustment chamber instead of water. The first and second charge-permeable membranes in this example can be anion-selective and cation-selective, respectively.

[0044] According to a further embodiment of the invention, the measuring arrangement can comprise a light source, a measuring chamber, a first optical waveguide arranged between the light source and the measuring chamber, a second optical waveguide arranged between the measuring chamber and a detector, and an evaluation unit.

[0045] The light source can be designed to produce one or more beams of light. For example, the light source can be designed to produce one or more beams of light of a specific wavelength. Examples include an LED lamp, a deuterium lamp (UV, ultraviolet light), a xenon flash lamp (UV, VIS), or a tungsten halogen lamp (VIS, visible light).

[0046] The measuring chamber can be formed by the first measuring chamber and / or the second measuring chamber. This can be understood to mean that the measuring chamber is formed by the first and second measuring chambers, or only by the first measuring chamber, or only by the second measuring chamber. If the first and / or second measuring chamber forms the measuring chamber, the measurement takes place directly in the respective measuring chamber; that is, the light beam generated by the light source passes (with a transmitted component) through the respective measuring chamber for measurement and is subsequently detected.

[0047] Alternatively, the measuring chamber can be located externally to the measuring cell. In this case, the measuring chamber can be filled with, or be filled with, the first and / or second liquid measuring chamber medium. This can be understood to mean that the measuring chamber is filled with both the first and second liquid measuring chamber medium. Alternatively, the measuring chamber can be filled only with the first liquid measuring chamber medium, or only with the second liquid measuring chamber medium. If the measuring chamber is located externally to the measuring cell, the first or second liquid measuring chamber medium can be conveyed to the measuring chamber, for example, by a liquid-conducting component. Multiple external measuring chambers can also be provided. An external measuring chamber could, for example, be a cuvette.

[0048] The first optical waveguide arranged between the light source and the measuring chamber can be configured to transmit the light beam from the light source to the measuring chamber, and the second optical waveguide arranged between the measuring chamber and a detector can be configured to transmit the light beam from the measuring chamber to the detector.

[0049] It is also conceivable to split the light beam generated by the light source into partial beams before it enters the first and second measuring chambers, for example, by means of a beam splitter. Alternatively, several light sources can be provided to generate multiple light beams, which can then be directed into the respective measuring chambers. In both cases, it can be provided that either a specific partial beam or a light beam generated by a specific light source is used to perform a zero measurement or calibration measurement in one of the measuring chambers (or a measuring chamber or chambers).

[0050] The detector can be designed to detect a transmitted portion of the light beam after the light beam has passed through the first and / or second liquid measuring chamber medium located in the measuring chamber.

[0051] The concentration of a light-absorbing substance in solution can be determined via the logarithmic intensity of light that a solution (e.g., a liquid measuring chamber medium) absorbs at a specific wavelength, the absorbance. The relationship between the absorbance A₂ at wavelength λ and the concentration c is described by the Lambert-Beer law: A λ = ε λ ∗ c ∗ d

[0052] This The extinction coefficient ελ is a wavelength- and material-specific constant, and d is the distance that the light travels through the sample (e.g., the measuring chamber).

[0053] The evaluation unit can be configured to qualitatively and / or quantitatively determine the cations and / or anions present in the ion-containing liquid medium based on a signal received from the detector. This can be understood as the evaluation unit being configured to determine both anions and cations, or only anions, or only cations, whereby the determination can be both qualitative and quantitative, or only qualitative, or only quantitative. First, anions and / or cations in the respective measuring chamber media can be determined quantitatively and / or qualitatively. Then, based on this, qualitative and / or quantitative conclusions can be drawn about the anions and / or cations in the ion-containing liquid medium. The evaluation unit can be understood as a computing unit or computer, or as a component of a computing unit or computer.A computing unit or computer can be stationary or portable. The evaluation unit can be located externally to the detector, in which case the detector and the evaluation unit are connected via suitable signal communication interfaces. The measurement setup (and thus also the evaluation unit) is preferably computer-aided, e.g., using the aforementioned computing unit or computer. The measurement setup (and thus also the evaluation unit) can rely on software, a routine, an algorithm, or the like that can be executed on the computing unit or computer for operation. The measurement setup, and in particular the evaluation unit, can be operated based on artificial intelligence (AI), for example, AI algorithms or corresponding (trainable) neural networks.The aforementioned computing unit or computer can contain all necessary interfaces, power supply and storage units, data storage, etc., required for the operation of the measurement setup. The aforementioned computing unit or computer can also include a control unit with which further components of the analysis system can be controlled and regulated.

[0054] In a further embodiment of the invention, the light source, the detector, and the evaluation unit (i.e., the measuring arrangement) are arranged externally to the measuring cell. Alternatively, the light source, the detector, and the evaluation unit (i.e., the measuring arrangement) are combined in a common unit (e.g., a common housing). In an external arrangement, the detector, the evaluation unit, and the light source can also be arranged in a common housing. Optionally, all components can be operated by a common processing unit. Preferably, the housing is made of a weight-saving material, e.g., plastic.

[0055] According to a further embodiment of the invention, the sample chamber has an inlet for receiving the ion-containing liquid medium. An inlet can have one or more openings through which the ion-containing liquid medium can be poured or flowed in. Other liquids, e.g., rinsing fluids, can also enter the sample chamber via such an inlet. The one or more openings can be closable (with suitable closing means). The inlet can include a seal. The same applies analogously to an outlet of the sample chamber, which can also include one or more openings. The one or more openings of the outlet can also be closable. Ionic liquid medium can be discharged from the sample chamber, and thus from the measuring cell, via the outlet.

[0056] The sample chamber can either be filled with the ion-containing liquid medium through the inlet, or the ion-containing liquid medium can flow through it via the inlet towards an outlet. If the sample chamber is flowed through via the inlet towards an outlet, the analysis system can further include a sample reservoir for the ion-containing liquid medium, which is connected to the inlet of the sample chamber via a fluid-conducting component, and a pump unit designed to pump the ion-containing liquid medium from the sample reservoir through the sample chamber via the fluid-conducting component.

[0057] According to a further embodiment of the invention, the analysis system can include a filter unit arranged between the pump unit and the inlet to filter the ion-containing liquid medium. The ion-containing liquid medium can be passed through a filter arranged in the filter unit, causing membrane-damaging substances to remain on the filter and thus be removed from the ion-containing liquid medium. The arrangement of a filter unit is particularly advantageous for the stability and selectivity of membranes, for example, cation- or anion-selective membranes, which can be degraded or blocked, especially under continuous exposure to the membrane-damaging substances. In the simplest case, a filter unit can be understood as a sieve. Furthermore, suitable filter materials can be used as long as they are capable of filtering the aforementioned membrane-damaging substances (e.g.,Filter paper, molecular sieve, silica, activated carbon, filter ceramics, nanopore filters, etc.).

[0058] According to a further embodiment of the invention, the electrodes arranged in the measuring chambers can be made of metal. The metal from which the first electrode in the first measuring chamber is made can be the same metal from which the second electrode in the second measuring chamber is made. Alternatively, the first electrode in the first measuring chamber and the second electrode in the second measuring chamber can be made of different metals and have different electrochemical potentials. For example, electrodes made of titanium or platinum can be used within the scope of the invention. Preferably, both the first electrode in the first measuring chamber and the second electrode in the second measuring chamber are made of titanium or platinum.Particularly preferred is both the first electrode in the first measuring chamber and the second electrode in the second measuring chamber each designed as a titanium sheet or platinum sheet.

[0059] As already mentioned, the first liquid measuring chamber medium in the first measuring chamber can contain a first recognition agent to form anion-recognition agent associations when anions pass into the first measuring chamber, and the second liquid measuring chamber medium in the second measuring chamber can contain a second recognition agent to form cation-recognition agent associations when cations pass into the second measuring chamber. The invention is not limited to a specific recognition agent for the formation of associations; rather, all known recognition agents suitable as association formers for the respective ions to be determined can be used within the scope of the invention.

[0060] In this context, a recognition agent can be understood as a chemical substance suitable for detecting ions in a liquid medium. The recognition agent is generally specifically designed for detecting certain ions. In other words, a particular recognition agent is typically suitable for detecting specific ions, i.e., specific cations or anions. Within the scope of the present invention, all known recognition agents can, in principle, be used for ion detection.

[0061] In connection with the present invention, the detection of ions by the detection agent can be based on the detection agent forming ion-detection agent associations with ions in a liquid medium, thereby causing a detectable change in the chemical or physical state of the liquid medium. This detectable chemical or physical change can consist, alternatively or cumulatively, of a change in the pH value, color, temperature, or light transmittance of the liquid containing ions. The detectability of the chemical or physical change of state can be understood as the ability to detect the change in the chemical or physical state by means of a measurement, such as a photometric measurement.

[0062] In connection with the present invention, the recognition agents can be, for example, complex indicators or metal indicators, and the ion-recognition agent associations can accordingly be metal cation-metal indicator complexes. In this context, metal indicators can be understood as recognition agents that form reversible complexes with metal ions. Reversible complexes can be understood as chemical compounds consisting of a coordination center or central ion, such as a metal ion, and ligands, for example, chelating ligands. Chelating ligands can be understood as ligands that bind to a central ion via multiple coordination sites to form a chelate complex.The chemical bond between the coordination center and the ligand can be understood as a coordinate chemical bond, originating from the ligand, which donates electron density to the coordination center via lone pairs of electrons. Since the coordinate chemical bond is significantly weaker than a covalent chemical bond, the formation of the complex is a reversible process in which the reversible complex, the unbound ligands, and the unbound central ion exist in a dynamic equilibrium. In this context, metal indicators represent a particularly suitable form of chelating agent, with the reversible metal-indicator complex formed from the metal ion and the metal indicator exhibiting a different detectable color than the pure, unbound metal indicator.Due to their structure, metal indicators are detection substances that can change both the color and pH of a liquid medium containing the metal ions to be tested and the metal indicator itself, or metal-indicator complexes formed from them, in a detectable manner. The metal indicator can, for example, be a dye such as an azo dye. The metal indicator available under the trade name Calmagit can be, for example, 2-hydroxy-5-methylbenzenalazo-1-(2-naphthol-4-sulfonic acid) (CAS number 3147-14-6, C₁₇H₁₄N₂O₅S).

[0063] Due to its high chemical stability, even in aqueous solution, calmagit is a particularly suitable detection agent. In a liquid ion-containing medium such as an aqueous solution, calmagit exists in a singly to triply deprotonated form, depending on the pH of the medium. The doubly deprotonated form serves as a metal indicator. Calmagit can be used, for example, to determine divalent cations such as calcium or magnesium cations, or trivalent cations such as aluminum cations.

[0064] In connection with the present invention, the recognition agents can furthermore be precipitating agents, and the ion-recognition agent associations can accordingly be ion-precipitating agent associations. A precipitating agent can be understood as a chemical compound that forms ion-precipitating agent associations with ions present in a liquid medium, which are insoluble in said medium and therefore precipitate out of the medium. The precipitation of an ion with a precipitating agent from a liquid medium, such as an aqueous solution, can be understood as the precipitation of a previously dissolved ion in the form of a precipitate consisting of ion-precipitating agent associations. In connection with the present invention, all known precipitating agents can be used.

[0065] The formation of ion-precipitant associations insoluble in the liquid medium allows the medium's light transmittance to be reduced in a detectable manner. The precipitant can be, for example, sodium tetraphenylborate (Na[B(C₆H₅)₄], CAS number 143-66-8), available under the trade name Kalignost. Kalignost is particularly suitable for the detection of potassium, ammonium, rubidium, cesium, and thallium ions.

[0066] According to one embodiment of the invention, the first recognition agent and / or the second recognition agent can be selected from the group consisting of Calmagit, Dimethylglyoxime, Calconcarboxylic acid, Xylenol orange, Eriochrome black T, Eriochrome blue black R, Ethylenediaminetetraacetate (EDTA), Oxalic acid, Kalignost, Murexide, Methylthymol blue, Metallphthalein, Pyrocatechin violet, 1-(2-Pyridylazo)-2-naphthol, 4-(2-Pyridylazo)resorcinol, Iron(III) chloride, or mixtures thereof. This can be understood to mean that both the first and the first recognition substance, or only the first recognition substance, or only the second recognition substance, is selected from the group consisting of Calmagit, Dimethylglyoxime, Calconcarboxylic acid, Xylenol orange, Eriochrome black T, Eriochrome blue black R, Ethylenediaminetetraacetate (EDTA), Oxalic acid, Kalignost, Murexide, Methylthymol blue, Metallphthalein, Pyricatechin violet, 1-(2-Pyridylazo)-2-naphthol, 4-(2-Pyridylazo)resorcinol, Iron(III) chloride, or mixtures thereof.Preferably, both the first and second recognition agents are selected from the group consisting of calmagite, dimethylglyoxime, calconcarboxylic acid, xylenol orange, eriochrome black T, eriochrome blue black R, ethylenediaminetetraacetate (EDTA), oxalic acid, kalignost, murexide, methylthymol blue, metal phthalein, pyrocatechol violet, 1-(2-pyridylazo)-2-naphthol, 4-(2-pyridylazo)resorcinol, iron(III) chloride, or mixtures thereof. Calmagite is particularly preferred as the second recognition agent.

[0067] The analytical method according to the invention, when carried out with the analytical system according to the invention, can be adapted to the conditions of different fields of application without significant effort by using different detection agents, without requiring any technical modifications to the analytical system. Furthermore, by selecting a suitable detection agent, for example a suitable metal indicator, the analysis is insensitive to interfering ions.

[0068] Within the scope of the invention, all known ions that may be present in the ion-containing liquid medium can be determined. Ions can be understood as electrically charged particles that arise from uncharged atoms or molecules through the loss or addition of electrons. Anions and cations can be monovalent or polyvalent.

[0069] Cations can generally be understood as positively charged ions that arise from uncharged atoms or molecules through the loss of electrons. Anions, on the other hand, can be understood as negatively charged ions that arise from uncharged atoms or molecules through the addition of electrons. When a voltage is applied between two electrodes, causing one electrode to become negatively polarized and the other positively polarized, cations dissolved in a liquid medium are attracted to the negatively charged electrode due to their positive charge, while anions are attracted to the positively charged electrode due to their negative charge.

[0070] According to one embodiment of the invention, cations present in the ion-containing liquid medium, such as iron(II) ions, iron(III) ions, copper(II) ions, magnesium(II) ions, calcium(II) ions, manganese(II) ions, potassium(I) ions, ammonium cations (NH₄⁺), or mixtures thereof, can be determined. Alternatively or cumulatively, anions present in the ion-containing liquid medium, such as nitrate ions (NO₃⁻), nitrite ions (NO₂⁻), phosphate ions (PO₄³⁻), or mixtures thereof, can be determined. Preferred are the cations present in the ion-containing liquid medium that are to be determined, namely iron(II) ions, iron(III) ions, copper(II) ions, magnesium(II) ions, calcium(II) ions, manganese(II) ions, potassium(I) ions, ammonium cations (NH₄⁺), or mixtures thereof, and the anions present in the ion-containing liquid medium that are to be determined, namely nitrate ions (NO₃⁻), nitrite ions (NO₂⁻), phosphate ions. (PO 4 3-< ), or mixtures thereof.

[0071] Furthermore, the first and / or second liquid measuring chamber medium can comprise a further complexing agent. A further complexing agent can be understood as any chemical substance capable of masking interfering substances contained in the measuring chamber media. Masking of interfering substances can be understood as the complexation of the interfering substances by the further complexing agent, whereby the interfering substances are converted into masked substances. Masked substances can be understood as substances that are no longer capable of interfering with the analytical method according to the invention, in particular photometric measurements in the measuring chambers. The further complexing agent can be regenerated analogously to the regeneration of recognition substances described herein.

[0072] According to a further embodiment of the invention, the first and / or second liquid measuring chamber medium can comprise an electrolyte to increase its conductivity. In the context of the present invention, an electrolyte can be understood as a chemical substance added to the first and / or second liquid measuring chamber medium that is suitable for increasing the conductivity of the respective measuring chamber medium. In this context, the electrolyte, upon addition to a measuring chamber medium, can dissociate into its ions and, when a voltage is applied between electrodes arranged in the measuring chambers, conduct the electric current under the influence of the resulting electric field, thereby increasing the conductivity of the measuring chamber medium compared to a measuring chamber medium that does not contain an electrolyte. Conductivity is defined as the ability to conduct electric current. In principle, all known electrolytes can be used.Sodium sulfate is a particularly preferred electrolyte.

[0073] Alternatively, to increase the conductivity of the liquid medium, an ion exchange material can be placed in the sample chamber. In this case, the liquid medium flows through the ion exchange material, binding ions of one type to the material and releasing an equivalent amount of charge from ions of another type previously bound to the material into the medium, thereby increasing the conductivity of the liquid medium. An ion exchange material can be understood as a material that can exchange one type of ion originally present in the liquid medium for another type of ion originally bound to the ion exchanger. Examples of ion exchange materials include aluminum oxide, chlorophyll, cholestyramine, colesevelam, a synthetic resin based on at least one polymer, or a zeolite such as Zeolite A (Sasil).

[0074] The ion exchange material can be a cation exchange material, an anion exchange material, or an amphoteric ion exchange material. In this context, a cation exchange material can bind one type of cation dissolved in the liquid, ion-containing medium and release a different type of cation, originally bound to the ion exchange material, into the medium. During the exchange process, one type of cation is exchanged for the other. Similarly, an anion exchange material can exchange anions of one type for anions of another. An amphoteric ion exchange material, in turn, can exchange both anions and cations simultaneously.

[0075] Cation exchange materials contain anionic functional groups on their surface, such as carboxylic acid or sulfonic acid groups, with dissociable cations. Anion exchangers, in turn, contain cationic functional groups, such as quaternary ammonium groups, which can exchange their counter-anion.

[0076] According to a further embodiment of the invention, the anion-selective membrane and / or the cation-selective membrane can each be made of a membrane material comprising a first and / or a second polymer material. The first polymer material contains functional groups arranged on a polymer material surface, which provide anion selectivity for the anion-selective membrane and / or cation selectivity for the cation-selective membrane. In principle, functional groups suitable for providing anion selectivity for an anion-selective membrane are those that are positively polarizable, thereby allowing anions to pass through the membrane while repelling cations and thus preventing them from passing through the membrane.Accordingly, such functional groups are suitable for providing cation selectivity of a cation-selective membrane, which are negatively polarizable, thereby allowing cations to pass through the membrane, but repelling anions and thus preventing them from passing through the membrane.

[0077] Preferably, the first polymer material is modified polystyrene (PS) with functional groups arranged on a polymer material surface. The functional groups arranged on the polymer material surface to provide the anion selectivity of the anion-selective membrane are generally positively polarizable functional groups, preferably quaternary amines. Alternatively or cumulatively, the functional groups arranged on the polymer material surface to provide the cation selectivity of the cation-selective membrane are negatively polarizable functional groups, preferably carboxylic acid or sulfonic acid groups.

[0078] The membrane material can further comprise a second polymer material for mechanical reinforcement of the corresponding anion-selective and / or cation-selective membrane. Mechanical reinforcement of a membrane can be understood as increased resistance of the membrane to mechanical influences, such as a mechanical shock, which can be achieved by incorporating a second polymer material into the membrane. The second polymer material comprises at least one polymer suitable for mechanical reinforcement. Preferably, the second polymer material is polyvinyl chloride (PVC), polypropylene (PP), or polyethylene terephthalate (PET).

[0079] According to a further embodiment of the invention, the analysis system can comprise a plurality of first and / or second measuring chambers. In particular, several pairs of first and second measuring chambers can be provided. Sample chambers can be arranged between the respective pairs, so that a plurality of measuring cells can be present, each consisting of a first measuring chamber, a second measuring chamber, and a sample chamber arranged between them. Several measuring cells can be advantageous in order to be able to qualitatively and / or quantitatively examine different types of ions in parallel or to ensure different measurement conditions (e.g., different detection substances, etc.).

[0080] According to a further embodiment of the invention, the analysis system can be arranged as a compact probe with an integrated pump unit directly in a sample reservoir. A sample reservoir can be a static or flowing medium to be analyzed, for example, a standing or flowing body of water such as a lake or river, or an industrial standing or flowing medium such as a flow-through reactor. Wastewater treatment plants, water purification plants, etc., can also provide static or flowing media that can be analyzed with the described system. Similarly, an aquarium filled with water can also serve as a sample reservoir. The water contained in an aquarium can constitute the static or flowing medium to be analyzed.An analysis system in the form of a compact probe with an integrated pump unit has the advantage, among others, that the compact probe is very easy and inexpensive to manufacture and maintain, and can be placed directly in a sample reservoir, thus enabling very precise measurements, even in the course of a real-time measurement, such as an online or inline measurement.

[0081] Alternatively, the analysis system can also be designed as a compact probe without a pump unit. In this case, the analysis system can be positioned directly in a sample reservoir containing a flowing medium (e.g., flowing water) at a specific flow rate. Due to the flow rate of the medium, there is no need to pump the ion-containing liquid through the sample chamber, thus eliminating the need for a pump unit. Such an analysis system is advantageous because it is simple and inexpensive to manufacture, use, and maintain. In this case, too, the sample reservoir can be an aquarium.

[0082] Alternatively, the analysis system can be positioned externally next to a sample reservoir (containing a flowing or static medium to be analyzed). The sample chamber is then filled with ion-containing liquid medium from the reservoir. Ionic liquid medium can also be introduced (e.g., pumped) from such a reservoir into the sample chamber. In this case as well, the sample reservoir can be an aquarium.

[0083] As already mentioned, the problem underlying the present invention is also solved by an analysis method according to claim 13. The aforementioned analysis method comprises at least the following process steps S2 and S3: S2: photometric measurement of anions, anion-recognition compound associations, cations and / or cation-recognition compound associations using the measurement setup, S3: qualitative and / or quantitative determination of the anions and / or cations based on the photometric measurement in step S2.

[0084] This concerns procedure step S2 Photometric measurement of anions and / or anion-recognition substance associates located in the first measuring chamber using the measuring arrangement, and / or photometric measurement of cations and / or cation-recognition substance associates located in the second measuring chamber using the measuring arrangement.

[0085] The procedural step S3 then involves the qualitative and / or quantitative determination of the anions and / or cations based on the photometric measurement in step S2. Step S3 can be carried out in particular with an evaluation unit that has already been described in several places.

[0086] This can be understood in terms of the following three alternatives.

[0087] In a first alternative, in step S2, the anions and / or anion-recognizant assemblies present in the first measuring chamber can be measured photometrically using the measuring setup. Thus, anions and anion-recognizant assemblies can be measured photometrically. Alternatively, only anions or only anion-recognizant assemblies can be measured photometrically.

[0088] Based on the respective photometric measurement(s) in step S2, the anions are then determined qualitatively and / or quantitatively in step S3. This can be understood as the determination of the anions being carried out both qualitatively and quantitatively. Alternatively, the determination of the anions can be carried out only quantitatively or only qualitatively. The qualitative and / or quantitative determination can be performed, in particular, with an evaluation unit that has already been described in several places.

[0089] Alternatively, in step S2, the cations and / or cation-recognizant compounds present in the second measuring chamber can be measured photometrically using the measuring setup. This can be understood as the photometric measurement of cations and cation-recognizant compounds. Alternatively, only cations or only cation-recognizant compounds can be measured photometrically. Based on the respective photometric measurement(s) in step S2, the cations are then determined qualitatively and / or quantitatively in step S3. This can be understood as the determination of the cations being carried out qualitatively and quantitatively. Alternatively, the determination of the cations can be carried out quantitatively only or qualitatively only. The qualitative and / or quantitative determination can be performed, in particular, with an evaluation unit that has already been described in several sections.

[0090] Furthermore, the measuring setup in step S2 can be used to measure both the anions and / or anion-recognition compound associations present in the first measuring chamber, and the cations and / or cation-recognition compound associations present in the second measuring chamber. Based on the respective photometric measurement(s) in step S2, the anions and cations are then determined qualitatively and / or quantitatively in step S3. This can be understood as the determination of the anions and cations being carried out simultaneously, both qualitatively and quantitatively. Alternatively, the determination of the anions and cations can be performed only quantitatively or only qualitatively. The qualitative and / or quantitative determination can be carried out, in particular, with an evaluation unit that has already been described in several sections.

[0091] Photometric measurement is a method used to analyze the composition of liquid media, for example, the ions they contain, using a light source. In photometric analysis, a chemical substance can be analyzed based on its specific color reaction and light absorption at a particular wavelength, depending on its chemical properties. For a photometric measurement, a light beam is generated by a light source and passed through a measuring chamber. A portion of the transmitted light beam then exits the chamber and is subsequently detected by a detector. This transmitted portion can be understood as a light beam with reduced intensity compared to the light beam introduced into the measuring chamber.The reduction in light intensity can be attributed to interactions such as absorption, scattering, diffraction, or reflection of the light beam with the medium in the measuring chamber, which contains the ions under investigation. Transmission (extinction, absorbance) can be understood as a measure of the opacity of the ion-containing medium under investigation, which is described by the following equation: . E = log I 0 / I D = log 1 / D where I 0 : intensity of the light beam before passing through the measuring space, ID : intensity of the light beam after passing through the measuring space, D : light transmittance ID / I 0 .

[0092] Photometric analysis (which can be performed with the described measuring setup) is characterized by speed, high selectivity, and short processing time. It is particularly important for the precise detection of low concentrations of ions in a liquid medium, for example, for determining trace metals. The light beam generated by the light source is preferably based on ultraviolet (UV) or visible (VIS) light. Photometric measurement allows the transmission of a liquid medium to be measured as a function of the wavelength of the incident light, yielding a transmission spectrum. From this transmission spectrum, the ions can then be qualitatively identified by means of characteristic features, and / or quantitatively determined using suitable computational methods.Characteristic features of the transmission spectrum can be characteristic curve features, such as peaks, maxima, minima, inflection points, slopes, smoothness, curvature, wavelength-dependent positions (or shifts) of the aforementioned features, or spacings between characteristic curve features in the spectrum. Ratios of characteristic curve features (e.g., ratios of averaged intensities or the like) can also be used for evaluation. Qualitative and / or quantitative determination can be carried out, in particular, with an evaluation unit that has already been described in several places.

[0093] Another optional step, S1, also concerns, Formation of anion-detection compound associations from anions located in the first measuring chamber and the first detection compound, and / or formation of cation-detection compound associations from cations located in the second measuring chamber and the second detection compound.

[0094] The dependent claims relate to advantageous embodiments and further developments of the present invention. The features mentioned in the dependent claims can be used in any combination to further develop the analytical method according to the invention, insofar as this is technically feasible. This also applies if such combinations are not expressly clarified by corresponding cross-references in the claims. In particular, this also applies across the category boundaries of the patent claims.

[0095] According to an advantageous embodiment of the method according to the invention, a step S0-a can be performed upstream of the optional step S1, or upstream of step S2. Step S0-a involves applying a voltage between the first electrode and the second electrode, thereby polarizing the first electrode positively and the second electrode negatively, and thereby transporting anions from the sample chamber through the anion-selective membrane towards the first electrode located in the first measuring chamber, and cations from the sample chamber through the cation-selective membrane towards the second electrode located in the second measuring cell.

[0096] According to a further advantageous embodiment of the analytical method according to the invention, a step S0-b can be performed upstream of the optional step S1, or upstream of step S2. Step S0-b involves adjusting the pH value of the first liquid measuring chamber medium contained in the first measuring chamber and / or the second liquid measuring chamber medium contained in the second measuring chamber using an analytical system according to claim 3.

[0097] According to a further advantageous embodiment of the analysis method according to the invention, a step S4 can be carried out after step S3, or upstream of step S0-a. Step S4 involves applying a voltage between the first electrode and the second electrode that is the opposite of the voltage applied in step S0-a, thereby polarizing the first electrode negatively and the second electrode positively.

[0098] This will, The anion-recognition agent associations formed in the first measuring chamber in the optional step S1 are converted back to anions and the first recognition agent, and the anions are transported from the first measuring chamber back through the anion-selective membrane into the sample chamber, thereby regenerating the first recognition agent, and / or the cation-recognition agent associations formed in the second measuring chamber in the optional step S1 are converted back to cations and the second recognition agent, and the cations are transported from the second measuring chamber back through the cation-selective membrane into the sample chamber, thereby regenerating the second recognition agent.

[0099] In principle, all procedural steps relating to measurement and / or evaluation can be computer-aided, i.e., using a suitable computing unit. Such a computing unit can rely on computational routines, algorithms, software, etc. As mentioned, such a computing unit can be a computer. A computing unit can be programmable.

[0100] Further advantages, embodiments, and refinements related to the analytical system or analytical method according to the invention are explained in more detail with reference to the exemplary embodiments described below. These are intended to clarify the invention for those skilled in the art and enable them to implement it without limiting the invention. Reference is made to the following figures in connection with the description of the aforementioned exemplary embodiments, which provide a more detailed explanation of the analytical system or analytical method according to the invention. For example, the figures show... Figure 1 is a schematic representation of a measuring cell used in an embodiment of the analysis system according to the invention; Figure 2 is a schematic representation of an analysis system according to an embodiment of the invention; Figure 3 is an exemplary absorption spectrum of calconcarboxylic acid as an example of a detection agent; Figure 4 is an exemplary absorption spectrum of calmagit as a further example of a detection agent; Figure 5 shows absorption spectra of various metal indicators together with various ions to be determined.

[0101] Figure 1 shows a measuring cell 1 which is used in an analysis system according to the invention. Figure 2 The analysis system is used for the qualitative and / or quantitative determination of ions in an ion-containing liquid medium 9. The ions can be cations K or anions A. As in Figure 1As shown, the measuring cell comprises a first measuring chamber 3, a second measuring chamber 4, and a sample chamber 2 arranged between the first measuring chamber 3 and the second measuring chamber 4, wherein the sample chamber 2 is designed to hold the ion-containing liquid medium 9. Figure 1Figure 1 shows an exemplary sample chamber 2 through which an ion-containing liquid medium 9 flows. A first electrode 5 is arranged in the first measuring chamber 3, and a second electrode 6 is arranged in the second measuring chamber 4. A voltage can be applied between the first and second electrodes 5, 6, making the first electrode 5 positively polarizable and the second electrode 6 negatively polarizable, thus allowing the anions A to be transported towards the first electrode 5 and the cations K towards the second electrode 6. An anion-selective membrane 7 is arranged between the first measuring chamber 3 and the sample chamber 2, and a cation-selective membrane 8 is arranged between the second measuring chamber 4 and the sample chamber 2. The anion-selective membrane 7 is designed to allow the passage of anions A from the sample chamber 2 into the first measuring chamber 3.The cation-selective membrane 8 is designed to allow the passage of cations K from the sample chamber 2 into the second measuring chamber 4. The first measuring chamber 3 is filled with a first liquid measuring chamber medium. This first liquid measuring chamber medium can be the ion-containing liquid medium 9. Optionally, the first liquid measuring chamber medium contains a first detection agent E-1 to form anion-detection agent associations AE-1 when anions A pass into the first measuring chamber 3. The second measuring chamber 4 is filled with a second liquid measuring chamber medium. Optionally, the second liquid measuring chamber medium contains a second detection agent E-2 to form cation-detection agent associations KE-2 when cations K pass into the second measuring chamber 4.

[0102] Figure 2 The measuring cell shows Figure 1in a highly schematic form, as well as a measuring setup. The measuring setup is designed to photometrically measure the anions A and / or anion-recognition compound AE-1 present in the first measuring chamber 3, and to determine the anions A qualitatively and / or quantitatively based on this measurement(s). Alternatively or additionally, the measuring setup is designed to photometrically measure the cations K and / or cation-recognition compound KE-2 present in the second measuring chamber 4, and to determine the cations K qualitatively and / or quantitatively based on this measurement(s).

[0103] As shown in the figure, the measuring arrangement comprises a light source 10, which is configured to generate a light beam. Furthermore, the measuring arrangement comprises a measuring chamber, wherein, according to the present example, the measuring chamber is formed by the first measuring chamber 3 and the second measuring chamber 4.

[0104] A first optical waveguide 12a is arranged between the light source 10 and the first measuring chamber 3 and the second measuring chamber 4 (these function as measuring spaces). This waveguide is configured to transmit the light beam from the light source 10 to the measuring space (i.e., the first measuring chamber 3 and the second measuring chamber 4). A second optical waveguide 12b is arranged between the first measuring chamber 3 and the second measuring chamber 4 and a detector 13. This waveguide is configured to transmit the light beam from the first measuring chamber 3 and the second measuring chamber 4, respectively, to the detector 13. The detector 13 is configured to detect a transmitted portion of the light beam after it has passed through the first or second liquid measuring chamber medium located in the measuring space.Furthermore, an evaluation unit 14 is provided, which is designed to qualitatively and / or quantitatively determine the cations and / or anions present in the ion-containing liquid medium 9 based on a signal received from the detector 13. The light source 10, the detector 13, and the evaluation unit 14 are arranged in an external part (e.g., a housing 11) to the measuring cell 1. The evaluation unit 14 is operated by a user 15 and can be programmed or read out by them.

[0105] Figure 2 The figure further shows that ion-containing liquid medium 9 is conveyed from a sample reservoir 18 into the sample chamber 2 via a liquid-conducting component 17 (e.g., a pipe, tube, hose, or the like). The ion-containing liquid medium is also removed from the sample chamber 2, for example, using a pump unit 16.

[0106] Figure 5This figure shows the position of the absorption maxima of various metal cation-metal indicator complexes after corresponding photometric measurement. Good distinguishability of the metal cations can be expected if the absorption maxima are as far apart as possible and do not overlap. This is particularly the case for calmagite and calconcarboxylic acid, which is why in Figures 3 and 4 corresponding absorption spectra of calcocarboxylic acid alone ( Fig. 3 ) and Calmagit alone ( Fig. 4 ) compared to the absorption spectra of calcocarboxylic acid ion associates (with the ions Cu 2+< , Ca 2+< , Fe 3+< , Mg 2+< and Fe 2+< ) in Figure 3 or calmagrite ion associates (with the ions Cu 2+< , Ca 2+< , Fe 3+< , Mg 2+< and Fe 2+< ) in Figure 4The measurements were performed at concentrations of calconcarboxylic acid and calmagit, respectively, and ion concentrations of 0.0001 M (except for Ca²⁺, which was 0.001 M). The pH was adjusted to 10 using a 0.5 M ammonium / ammonia buffer solution. Figures 3 and 4 The results show that the absorption curves of the recognition compound ion associations shift compared to the pure recognition compounds, and that the respective absorption curves exhibit different curve characteristics. Based on this alone, the aforementioned cations can be qualitatively differentiated. This can also be done, for example, by comparing the respective curves with database or literature data.

[0107] The following describes an exemplary method for the quantitative determination of cations (here Cu 2+< ) using an analysis system or method according to the invention, based on an exemplary calculation / derivation using Calmagit as a recognition agent.

[0108] The Rank Annihilation Factor Analysis (RAFA) method for analyzing spectroscopic data, such as those from UV-Vis spectroscopy, is a well-established technique. This allows for the more detailed investigation of metal indicators (detection agents) and the determination of their complex formation constants with a specific metal, as well as the extinction coefficients of the resulting metal-indicator complexes, which are not directly accessible experimentally. In this example, a model would first need to be created that calculates the absorbance of samples with specific initial concentrations of indicator and metal salt from the two aforementioned constants (complex formation constant and extinction coefficient). Subsequently, real samples are measured at the concentrations used in the model. The constants used in the model are varied, and the model's results are compared with the real data.In this example, the point with the smallest relative standard deviation between sample and model represents the optimum for the complex formation constant and the extinction coefficient.

[0109] Ion flow in systems such as the one described here can be described by the Nernst-Planck equation: J i = − D i ∗ ∇ c i − z i ∗ u i ∗ F ∗ c i ∗ ∇ ϕ

[0110] Ji describes the ion flux of ion i at this point. Di is the diffusion coefficient, ci the concentration at the point under consideration, zi the charge number, and ui the mobility of ion i. i, ϕ describes the electrical potential. The first term models diffusion and the second the ion flow due to the voltage applied in the cell.

[0111] A RAFA-like method can be used to determine the extinction coefficients of the metal-indicator complexes employed, as well as their complex formation constants. For this purpose, it is initially assumed that only the following reaction takes place between the metal ion (M²⁺< ) and the indicator (Ind²⁻< ): M 2 + + Ind 2 − ⇌ M Ind

[0112] The resulting complex will be abbreviated as M-Ind in the following. The law of mass action for this reaction can now be expressed using the complex formation constant. K Set up B: K B = M − Ind M 2 + ∗ Ind 2 −

[0113] Furthermore, the following apply The following dependencies exist for the concentrations at equilibrium compared to the original concentrations. ci : M 2 + = c M 2 + − M − Ind Ind 2 − = c Ind 2 − − M − Ind

[0114] In the following, [M-Ind] is abbreviated as x. Substituting equations 5 and 6 into equation 4 and rearranging yields equation 7: K B ∗ c Ind 2 − ∗ c M 2 + − K B ∗ c Ind 2 − + c M 2 + + 1 ∗ x + K B ∗ x 2 = 0

[0115] Solving equation 7 yields equation 8. Only the solution with a negative sign in front of the square root is valid. x = K B ∗ c Ind 2 − + c M 2 + + 1 − K B ∗ c Ind 2 − + c M 2 + + 1 2 − 4 ∗ K B 2 ∗ c Ind 2 − ∗ c M 2 + 2 ∗ K B

[0116] For the total absorbance Ages of the sample, the following equation is assumed to apply: A ges = A Ind 2 − + A M 2 + + A M − Ind + A 0

[0117] A0 is the absorbance when measuring the pure solvent. By substituting the Lambert-Beer law and equations 5 and 6, the following relationship is obtained: A ges = c Ind 2 − − x ∗ ε Ind 2 − + c M 2 + − x ∗ ε M 2 + + x ∗ ε M − Ind + A 0

[0118] The cuvette length can be normalized to 1 cm using a path length correction, allowing it to be omitted for simplification. The extinction coefficients for the pure salt εM²⁺ and for the pure indicator εInd²⁻ can be directly determined from the absorbances of pure solutions of these substances using the Lambert-Beer law. The total absorbance (Atotal) can then be determined by measuring a real solution with cInd²⁻ and εM²⁺. xThe inaccessible extinction coefficient of the metal-indicator complex ε M-Ind, which is accessible via equation 8, can now be determined using this data and by rearranging equation 10: ε M − Ind = A ges − c Ind 2 − − x ∗ ε Ind 2 − − c M 2 + − x ∗ ε M 2 + − A 0 x

[0119] To now KB and To determine εM-Ind, samples with different cInd ²< and εM ²< can be measured. Subsequently, KB can be varied over a wide range of values, and εM-Ind can be determined for each individual sample. For each KB used, the relative standard deviation σR among the εM-Ind can be determined using the following formula: σ R = ∑ i = 1 n ε M − Ind , i − ε M − Ind ^ 2 n − 1 ∗ 1 ε M − Ind ^

[0120] The optimal value for Ke is obtained at minimum σR. The optimal value for εM-Ind is determined at this point from the mean value of the individual εM-Ind of the individual samples. Analogous equations apply to the investigation of metal-indicator complexes with two indicator ligands per metal ion, based on the following law of mass action: K B = M − 2 Ind M 2 + ∗ Ind 2 − 2

[0121] A problem in calculating the metal ion concentrations in the measuring chamber (here, the second measuring chamber for cations) is that the absorbances of the unbound calmagité and those of the metal-calmagité complexes overlap. To solve this problem, equation 9 is extended and it is assumed that the metal ions not bound in the complex hardly absorb. A ges , λ = A Ind 2 − , λ + ∑ A M i − Ind , λ + A 0 , λ A ges , λ = ε Ind 2 − , λ ∗ Ind 2 − + ∑ ε M i − Ind ∗ M i − Ind + A 0 , λ

[0122] equation Equation 15 is obtained by substituting the Lambert-Beer law. The extinction coefficient of the indicator εInd 2-,λ at wavelength λ is already known from the described measurements. The extinction coefficients of the metal-indicator complexes εM i -Ind,λ are accessible through the data from the investigation of the metal-indicator complexes, since the concentrations of the individual substances in the investigated solution are determined. Thus, equation 11 can also be used at other wavelengths and the concentrations substituted. In order to determine the individual concentrations in the measuring cell itself, the absorbance must be determined at i+1 wavelengths. Since the extinction coefficients of the substances present in solution can be determined at all wavelengths, one now obtains i +1 equations for the same number of unknown concentrations. Solving this system of equations yields the equilibrium concentrations. To determine the total concentrations of the metal ions in the system, equations 4 and 5 are used: c M , i = M i − Ind ∗ 1 + 1 K B , i ∗ Ind 2 −

[0123] The concentration of copper ions is calculated using an analogous equation based on equation 13.

[0124] To model the concentration in the measuring chambers, some assumptions must first be made. It must be assumed that ion diffusion through the membrane is negligible. Furthermore, the formation of boundary layers should initially be disregarded. Thus, the following simplified Nernst-Planck equation for the ion flux results. J i through the membrane: J i = − z i ∗ u i ∗ F ∗ c i ∗ ∇ ϕ

[0125] It is now assumed that the potential ϕ in the solution changes only linearly and that ∇ϕ is therefore constant. By rewriting this as a rate law, we obtain the following equation: − dc a dt = k ∗ c a Here, k describes the constants involved, and ca describes the concentration of the respective metal ion outside the measuring chamber, i.e., in front of the membrane. Integration yields the following equation: ∫ c a , 0 c a , 1 c − 1 ∗ dc = − k ∗ ∫ 0 t dt

[0126] Therefore: c a , 1 = c a , 0 ∗ e − k ∗ t c a , 1 − c a , 0 = Δ c a

[0127] Furthermore, the change in the measurable concentration in the measuring chamber Δc over the volume V this, as well as the volume of the external sample Va, The change in external concentration is approximately dependent on the ion migrating from the sample into the measuring chamber. This results in the following equation: Δ c a = − Δ c ∗ V V a

[0128] By substituting equations 21 and 22 into equation 20 and subsequently rearranging, a law for determining the initial external concentration with a known change in the internal concentration is obtained, which ultimately makes it possible to determine the concentration of the sample: c a , 0 = Δ c ∗ V V a 1 − e − k ∗ t

Claims

1. An analysis system for the qualitative and / or quantitative determination of ions in an ion-containing liquid medium (9), wherein the ions are cations (K) and / or anions (A), the analysis system comprising: - a measuring cell (1) comprising: a first measuring chamber (3), a second measuring chamber (4), and a sample chamber (2) arranged between the first measuring chamber (3) and the second measuring chamber (4), wherein the sample chamber (2) is designed to accommodate the ion-containing liquid medium (9), wherein a first electrode (5) is arranged in the first measuring chamber (3) and a second electrode (6) is arranged in the second measuring chamber (4), and wherein a voltage can be applied between the first and second electrodes (5, 6), whereby the first electrode (5) can be positively polarised and the second electrode (6) can be negatively polarised, and whereby the anions (A) can be transported towards the first electrode (5) and the cations (K) can be transported towards the second electrode (6), wherein an anion-selective membrane (7) is arranged between the first measuring chamber (3) and the sample chamber (2), and a cation-selective membrane (8) is arranged between the second measuring chamber (4) and the sample chamber (2), wherein the anion-selective membrane (7) is designed to enable a passage of anions (A) out of the sample chamber (2) into the first measuring chamber (3), and wherein the cation-selective membrane (8) is designed to enable a passage of cations (K) out of the sample chamber (2) into the second measuring chamber (4), wherein the first measuring chamber (3) is filled with a first liquid measuring chamber medium, and wherein optionally a first detection substance (E-1) is contained in the first liquid measuring chamber medium, in order to form anion detection substance associates (A-E-1) when anions (A) pass into the first measuring chamber (3), and wherein the second measuring chamber (4) is filled with a second liquid measuring chamber medium, and wherein optionally a second detection substance (E-2) is contained in the second liquid measuring chamber medium, in order to form cation detection substance associates (K-E-2) when cations (K) pass into the second measuring chamber (4), and - a measuring arrangement that is designed a. to measure the anions (A) and / or anion detection substance associates (A-E-1) present in the first measuring chamber (3) photometrically by way of a photometric measurement, and to determine the anions (A) qualitatively and / or quantitatively on the basis of this / these measurement(s), and / or b. to measure the cations (K) and / or cation detection substance associates (K-E-2) present in the second measuring chamber (4) photometrically by way of a photometric measurement, and to determine the cations (K) qualitatively and / or quantitatively on the basis of this / these measurement(s).

2. The analysis system according to claim 1, wherein a first mixing apparatus is arranged in the first measuring chamber (3) to mix the first liquid measuring chamber medium contained in the first measuring chamber (3), and / or wherein a second mixing apparatus is arranged in the second measuring chamber (4) to mix the second liquid measuring chamber medium contained in the second measuring chamber (4).

3. The analysis system according to claim 1 or 2, wherein in order to adjust a pH of the first liquid measuring chamber medium contained in the first measuring chamber (3) and / or of the second liquid measuring chamber medium contained in the second measuring chamber (4), a. a charge-permeable membrane is arranged between the first measuring chamber (3) and the second measuring chamber (4) to enable a charge to pass between the first measuring chamber (3) and the second measuring chamber (4), or b. a first charge-permeable membrane is arranged between the first measuring chamber (3) and a first water electrolysis chamber fitted with a first water electrolysis electrode, to enable a charge to pass between the first measuring chamber (3) and the first water electrolysis chamber, and / or a second charge-permeable membrane is arranged between the second measuring chamber (4) and a second water electrolysis chamber fitted with a second water electrolysis electrode to enable a charge to pass between the second measuring chamber (4) and the second water electrolysis chamber.

4. The analysis system according to claim 1, wherein the measuring arrangement comprises: - a light source (10) that is designed to generate a light beam, - a measuring space, wherein the measuring space a. is formed by the first measuring chamber (3) and / or the second measuring chamber (4), or b. is arranged outside the measuring cell (1), wherein the measuring space can be filled with the first and / or second liquid measuring chamber medium, - a first optical waveguide (12a) arranged between the light source (10) and the measuring space, which waveguide is configured to guide the light beam from the light source (10) to the measuring space, and a second optical waveguide (12b) arranged between the measuring space and a detector (13), which waveguide is configured to guide the light beam from the measuring space to the detector (13), wherein the detector (13) is designed to detect a transmitted component of the light beam after the light beam has passed through first or second liquid measuring chamber medium located in the measuring space, and - an evaluation unit (14), which is designed to determine cations and / or anions present in the ion-containing liquid medium (9) qualitatively and / or quantitatively on the basis of a signal received from the detector (13).

5. The analysis system according to claim 4, wherein the light source (10), the detector (13) and the evaluation unit (14) are arranged outside the measuring cell (1).

6. The analysis system according to claim 1, wherein the sample chamber (2) has an inlet for receiving the ion-containing liquid medium (9), wherein the sample chamber (2) a. can be filled with the ion-containing liquid medium (9) through the inlet, or b. the ion-containing liquid medium (9) can flow through the sample chamber from the inlet towards an outlet, wherein the analysis system further comprises: - a sample reservoir (18) for the ion-containing liquid medium (9), which is connected to the inlet of the sample chamber (2) via a liquid-carrying component (17), - a pump unit (16) which is designed to pump the ion-containing liquid medium (9) out of the sample reservoir (18) and through the sample chamber (2) via the liquid-conducting component (17).

7. The analysis system according to claim 6, further comprising a filter unit arranged between the pump unit (16) and the inlet in order to filter the ion-containing liquid medium (9) .

8. The analysis system according to any one of the preceding claims, wherein the electrodes (5, 6) are made from the same metal or different metals, for example titanium or platinum.

9. The analysis system according to any one of the preceding claims, wherein the first detection substance (E-1) and / or the second detection substance (E-2) is selected from the group: calmagite, dimethylglyoxime, calcon carboxylic acid, xylenol orange, eriochrome black T, eriochrome blue black R, ethylenediamine tetraacetate (EDTA), oxalic acid, Kalignost, murexide, methylthymol blue, metal phthalein, pyrocatechol violet, 1-(2-pyridylazo)-2-naphthol, 4-(2-pyridylazo) resorcinol, iron (III) chloride, or mixtures thereof.

10. The analysis system according to any one of the preceding claims, wherein the cations are selected from the group: iron(II) ions, iron(III) ions, copper (II) ions, magnesium (II) ions, calcium (II) ions, manganese (II) ions, potassium(I) ions, ammonium cations (NH4+), or mixtures thereof, and / or wherein the anions as selected from the group: nitrate ions (NO3-), nitrite ions (NO2-), phosphate ions (PO43-), or mixtures thereof.

11. The analysis system according to any one of the preceding claims, wherein the first and / or second liquid measuring chamber medium comprises an electrolyte, preferably sodium sulfate.

12. The analysis system according to any one of the preceding claims, wherein the anion-selective membrane (7) and / or the cation-selective membrane (8) are each made from a membrane material that comprises: - a first polymer material, preferably modified polystyrene (PS), with functional groups arranged on a polymer material surface, wherein the functional groups arranged on the polymer material surface functional groups lend an anion selectivity to the anion-selective membrane (7) and / or a cation selectivity to the cation-selective membrane (8), wherein the functional groups arranged on the polymer material surface for lending anion selectivity to the anion-selective membrane (7) are preferably quaternary amines, and / or wherein the functional groups arranged on the polymer material surface for lending cation selectivity to the cation selective membrane (8) are preferably carboxylic acid or sulfonic acid groups, - a second polymer material for mechanical strengthening of the anion-selective membrane (7) and / or the cation-selective membrane (8), preferably polyvinyl chloride (PVC), polypropylene (PP) or polyethylene terephthalate (PET).

13. An analysis process for qualitative and / or quantitative determination of ions in an ion-containing liquid medium (9) using the analysis system according to any one of claims 1-12, said process comprising the following steps: - SO-a: application of a voltage between the first electrode (5) and the second electrode (6), whereby the first electrode (5) is positively polarised and the second electrode (6) is negatively polarised, and whereby anions (A) are transported from the sample chamber (2), through the anion-selective membrane (7) towards the first electrode (5) arranged in the first measuring chamber (3), and cations (K) are transported from the sample chamber (2), through the cation-selective membrane (8) towards the second electrode (6) arranged in the second measuring cell (4), - S1: forming anion detection substance associates (A-E-1) from anions (A) present in the first measuring chamber (3) and the first detection substance (E-1), and / or forming cation detection substance associates (K-E-2) from cations (K) present in the second measuring chamber (4) and the second detection substance (E-2), - S2: photometric measurement of anions (A) and / or anion detection substance associates (A-E-1) present in the first measuring chamber (3) with the measuring arrangement, and / or photometric measurement of cations (K) and / or cation detection substance associates (K-E-2) present in the second measuring chamber (4) with the measuring arrangement, - S3: qualitative and / or quantitative determination of the anions (A) and / or cations (K) on the basis of the photometric measurement in step S2.

14. The analysis process according to claim 13, wherein the following step is performed prior to the optional step S1, or prior to step S2: - S0-b: adjustment of a pH of the first liquid measuring chamber medium contained in the first measuring chamber (3) and / or of the second liquid measuring chamber medium contained in the second measuring chamber (4) with an analysis system according to claim 3.

15. The analysis process according to claim 13, wherein the following step is performed after step S3 or prior to step SO-a: - S4: application of a reverse voltage compared to the voltage applied in step S0-a between the first electrode (5) and the second electrode (6), whereby the first electrode (5) is negatively polarised and the second electrode (6) is positively polarised, whereby the anion detection substance associates (A-E-1) formed in the first measuring chamber (3) in optional step S1 are reverted to anions (A) and the first detection substance (E-1), and anions (A) are transported from the first measuring chamber (3) through the anion-selective membrane (7) back into the sample chamber (2), whereby the first detection substance (E-1) is regenerated, and / or whereby the cation detection substance associates (K-E-2) formed in the second measuring chamber (4) in optional step S1 are reverted to cations (K) and the second detection substance (E-2), and cations (K) are transported from the second measuring chamber (4) through the cation-selective membrane (8) back into the sample chamber (2), whereby the second detection substance (E-2) is regenerated.

16. The analysis system according to any one of claims 1-12, wherein the analysis system as a compact probe with integrated pump unit is arranged directly in a sample reservoir.