Method and device for DC voltage-controlled adsorption and desorption on charged membranes

Description

[0001] Membranes, especially polymer membranes, are typically used for the mechanical retention of substances, biomolecules, viruses, and bacteria. The retention rate is determined by the pore size, and the flow rate is determined by the porosity, the proportion of pores in the membrane matrix.

[0002] So-called chromatographic membranes have been developed from polymer membranes. In addition to mechanical retention properties, these membranes possess additional properties that lead to the adsorption of charged substances. These membranes exhibit a specific surface conditioning or chromatographic properties are created by the incorporation of substances.

[0003] From EP 0 860 888 A1 it is known to coat a membrane with metal using a metal ion beam.

[0004] From WO 2018 / 122,315 A1 and EP 3 115 099 A1 it is known to apply a voltage to a metal-coated membrane relative to a counter electrode.

[0005] From JP H 01301879A it is known to coat ion exchange membranes with metal by means of electroplating.

[0006] WO 00 / 50161 describes a positively charged membrane. The surface of the porous membrane matrix, consisting of, for example, polyaromatics, polysulfones, polyolefins, polystyrenes, polyamides, polyimides, fluoropolymers, polycarbonates, polyesters, cellulose acetate, or cellulose nitrate, is charged by crosslinking it with a polymer structure containing attached positively charged cationic groups, such as quaternary ammonium groups. These are bound to the polymer structure of the membrane via covalent bonding. This so-called chromatographic membrane now has a positive charge that remains positive regardless of the pH value of the solution to be filtered. Using this positively charged surface, negatively charged biomolecules such as albumin (BSA) can be adsorptively bound. WO 00 / 50161 describes that a binding capacity based on BSA of 25 mg / ml (ml of membrane volume) or more can be achieved.

[0007] The binding capacity can be determined by determining the amount of adsorbed substance. This can be done, for example, by filtering through the membrane and determining the concentration before and after passage through the membrane, as well as determining the flux through the membrane.

[0008] The concentration can be determined in several known ways. For example, it can be determined photometrically.

[0009] For this purpose, a UV / VIS spectrophotometer, e.g. Aqualytic type XD7000, with a wavelength range between 190 and 1100 nm, a resolution of 1 nm, a photometric resolution of: absorption: 0.001 and / or transmission: 0.1% can be used.

[0010] For example, an inline measurement of the filtrate, which is fed through the measuring cell (cuvette) via a fine capillary, can be performed during the ongoing process. This can be used to determine how long the added proteins are completely retained, i.e., whether the filtrate is protein-free. If a solution of known concentration is added and the flow rate through the membrane is determined, it can be determined how much the membrane can adsorb before breakthrough occurs. This amount, relative to the membrane volume, is the binding capacity.

[0011] WO 00 / 50160 describes a negatively charged membrane. The surface of the porous membrane matrix, consisting of, for example, polyaromatics, polysulfones, polyolefins, polystyrenes, polyamides, polyimides, fluoropolymers, polycarbonates, polyesters, cellulose acetate, or cellulose nitrate, is charged by crosslinking it with a polymer structure containing attached negatively charged anionic groups, such as hydroxyl groups. These are bound to the polymer structure of the membrane via covalent bonding. This so-called chromatographic membrane now has a negative charge that remains positive regardless of the pH value of the solution being filtered. Positively charged substances or proteins can then be bound by means of the negative charge. WO 00 / 50160 describes a binding capacity of lysozyme of 25 mg / ml or more.

[0012] AU 2014277783 B2 describes a membrane structure consisting of two membrane layers between which silicon nanoparticles are bound in a mass. The two membrane layers can be positively or negatively charged, or one positively and the other negatively charged. The silicon particles bound in a mass can also have a charge.

[0013] The products listed in these examples are used to separate biomolecules. For example, viruses can be separated from proteins. The pH value of the solution to be filtered is selected to correspond to the isoelectric point of a protein to be isolated. If this solution is filtered through a positively charged membrane with pores large enough to prevent proteins from being mechanically retained (e.g., 0.2 µ m, 0.4 µ m or 0.8 µm), the proteins pass through this membrane because they have no charge at the isoelectric point. All other substances that have a negative charge at the set pH value, such as viruses, are then bound by adsorption. These chromatographic properties allow proteins to be purified.

[0014] Biomolecules can also be concentrated via a positively or negatively charged membrane. The target molecules are bound by adsorptive means and thus removed from a solution.

[0015] In a further step, the target molecules are desorbed again by changing the pH value or by pumping a highly saline solution through the membrane after adsorption of the target molecules. This can happen step by step. The salt content of the solution can be gradually increased. This means that substances with a weak charge are initially displaced from the binding sites of the membrane by the salt ions. Other substances with stronger bonds require a higher concentration of salt ions to be released from the binding sites of the membrane. Similarly, the pH value, which indicates the concentration of OH- or H+ ions, can be gradually changed and used to gradually detach adsorbed molecules of different charge strengths.By changing the pH value or by adding a large concentration of salt molecules (e.g. 1 molar NaCl solution), the large number of charged ions displace the target molecules from the binding sites.

[0016] In addition to the advantages of adsorptive properties in addition to mechanical retention, chromatographic membranes have certain disadvantages. Adsorbed substances can only be desorbed again if chemicals are added that exceed the existing binding force of the bound charged molecules. This usually occurs through a significant change in pH or the addition of a highly saline solution. Due to the ion concentration and strength, the bound molecules are replaced by salt ions or by hydrogen or hydroxide ions. Rinsing is then necessary to remove the pH change or the high salt content, thus restoring the membrane's chromatographic properties. In addition, the solution of the captured target molecules must also be neutralized and / or freed of its saline cargo.Target molecules, such as sensitive biomolecules, can be damaged by drastic pH changes or high salt concentrations. This also places limitations on the chromatographic membrane process. The greater the membrane's adsorptive binding forces, the higher the ion content of the desorption medium must be. However, excessively strong acids and alkalis, or salt concentrations, lead to increasing damage to the biomolecules being separated.

[0017] A further disadvantage is the determination of the binding capacity until breakthrough or termination after recovery. If the concentration of the target molecules in the solution is unknown, additional measurement methods such as UV / VIS spectrophotometry or conductivity measurement of the filtrate are necessary to prevent breakthrough of target molecules.

[0018] It is also known to apply a voltage to metallic membranes. However, this requires a constant and reliable voltage across the active surface to achieve or support a filtering effect, depending on the design. Furthermore, it is known, for example from EP 3 115 099 A1 or WO 2018 / 122315 A1, to apply a voltage to metallically coated polymer membranes. It is also known from EP 0 860 888 A1 to coat metallic membranes with a thin metal layer.

[0019] The inventive task is to adsorb the molecules simply and reliably and to simplify the desorption of adsorbed target molecules chromatographically bound to membranes, ideally without the addition of highly ionic substances such as acids, alkalis, or salts. Another task is to develop a readily measurable value that allows for the indication of the current and / or remaining binding capacity of the membrane during the adsorption process and / or its control.

[0020] This object is achieved according to the invention in that the adsorption takes place on a, in particular chemically, charged membrane and the desorption is achieved by physical, electromagnetic and / or by generating electric fields. This is achieved in particular by applying a thin metal layer to one or both sides of a, in particular chemically, positively or negatively charged membrane. Such a charged membrane has a charge, in particular without the application of a voltage. The metal layer is in particular so thin that it does not or hardly changes the porosity but in particular so thick that continuous conductivity of this layer is ensured. Metal(s) that cannot be oxidized or can only be oxidized with great difficulty, such as gold, platinum, palladium, are preferably used.

[0021] The metal layer(s) now serve as electrode(s) that can be charged with a direct current. The level of the applied direct current is preferably selected such that the generated electric fields achieve complete desorption of the adsorptively bound molecules. The problem is solved according to the method, in particular, by a method for separation by means of adsorption and electrodesorption, comprising the following steps: a. Providing a, in particular chemically charged, polymer membrane with a first planar and porous coating of metal at least on a first side of the polymer membrane, in particular as a working electrode, and providing a counter electrode, in particular as a second planar, porous coating on the other side of the membrane or providing a counter electrode independent of the membrane; b. I.Bringing the charged polymer membrane with a flat and porous metal coating and the counter electrode into contact with at least one first fluid, in particular flowing the at least one first fluid through the membrane, wherein the at least one first fluid is in particular a solution with charged, in particular at least two different, substances, in particular biomolecules, for adsorption on the charged surface (inner and / or outer) of the membrane, in particular without applying an additional voltage to the working electrode or by applying a voltage that is equal to the charge of the membrane charge to support the adsorption processes. b.II In particular adsorbing the at least one charged substance on the membrane, in particular during filtration of the solution, in particular until a certain, in particular predetermined, binding capacity and / or a predetermined proportion of the binding capacity of the charged membrane has been used for adsorption. c. Applying a direct voltage between the metal coating of the charged polymer membrane (working electrode) and the counter electrode, wherein in particular the direct voltage is applied in the opposite direction to the charge of the polymer membrane. d. Bringing into contact, in particular flowing through, the membrane with the at least one first fluid and / or a second fluid, which in particular contains no biomolecules for adsorption. In particular, the counter electrode is also brought into contact with the fluid with which the membrane is brought into contact. e.In particular, control of the voltage, in particular increase of the voltage which is opposite to the charge of the membrane for the defined and, in particular sequentially stepwise, desorption of, in particular at least two different substances, in particular biomolecules, which in particular have different charge strengths.

[0022] The volume can be, for example, a vessel. The fluid is, in particular, a liquid and / or, in particular, a solvent containing at least one substance, in particular a dissolved substance, in particular a molecule. The first liquid can, for example, be a solution containing proteins, peptides, or nucleic acids.

[0023] The additional fluid is, in particular, a liquid and / or, in particular, a solvent, in particular a pure solvent. In particular, the first fluid is removed from the first volume and / or the membrane is removed from the first volume and / or the first fluid and membrane are separated from each other. Removal is achieved, in particular, by draining the first fluid and / or flushing the fluid. Thus, it is not necessary for the first fluid to be completely removed; residues are tolerable in any case, but can also be flushed away.

[0024] However, the first fluid can be mixed with or replaced by the additional fluid. It is preferred to fill the additional fluid into the first volume after draining and, if necessary, flushing the first fluid and / or transferring the membrane from the first volume to a second volume, wherein the second volume is and / or is being filled with the additional fluid.

[0025] In particular, in step b, in particular bI and / or b.II, the adsorption of at least one substance contained in the first fluid takes place. This does not have to be done completely, but it can be done completely. The adsorption of a portion may be sufficient. Adsorption occurs in particular due to the charge of the membrane and / or due to the charge of the membrane and the additionally applied voltage.

[0026] In steps c, d, and / or e, in particular, a partial or complete desorption of what was adsorbed in step b, in particular of the at least one substance, takes place. The desorption takes place into the second fluid or into a mixture of the first and second fluids.

[0027] Step d and / or e takes place at least while the charged polymer membrane with a flat and porous metal coating and the counter electrode are in contact with the first and / or further fluid, in particular in the first and / or second volume. Step d and / or e can also be started before step c.

[0028] In order to desorb previously adsorptively bound biomolecules, the direct voltage is applied to a membrane, in particular a chemically positively charged (charged), in such a way that the metal coating connected to the membrane, acting as the working electrode, is supplied with a negative voltage. This is achieved, for example, by connecting the working electrode to the negative pole of a voltage source and the counter electrode to the positive pole of the voltage source. In the case of a membrane, in particular a chemically negatively charged (charged), the direct voltage is applied in such a way that the metal coating connected to the membrane, acting as the working electrode, is supplied with a positive voltage. This is achieved, for example, by connecting the working electrode to the positive pole of a voltage source and the counter electrode to the negative pole of the voltage source.

[0029] In particular, the method is a method for the chromatographic separation of charged molecules, in particular ion exchange chromatography or ion chromatography for short. Biomolecules are primarily separated based on their charge. The goal is to achieve better separation and / or identification of individual biomolecules by separating them according to charge (analysis) or to extract certain biomolecules from a solution as valuable materials. The extracted biomolecules of the same charge are, in particular, concentrated. For example, the at least one charged substance contained in the first fluid is extracted from the first fluid and transferred to the second fluid and / or concentrated in the first and / or second fluid.

[0030] If the membrane is coated with metal on both sides, i.e. a first and a second coating of metal between which the polymer membrane is arranged, the first coating can be used as the working electrode and the second coating as the counter electrode.

[0031] Advantageously, the method is carried out in particular in such a way and / or the device is designed in such a way that the first fluid in step b, in particular bI and / or b.II, flows in such a way that it flows from the working electrode to the counter electrode, the working electrode is then upstream, the counter electrode downstream.

[0032] Advantageously, the method is carried out in particular in such a way and / or the device is designed in such a way that the first fluid flows in step c, d and / or e in such a way that it flows from the working electrode to the counter electrode. In the case of a, in particular chemically, positively charged (charged) membrane, the direct voltage in step b, in particular bI and / or b.II, is applied in such a way that the working electrode is supplied with a positive direct voltage. This occurs in particular as long as an adsorption process is taking place. The adsorption process by the positively charged membrane can also take place without a voltage supply to the working electrode, but can be intensified by the additional voltage.

[0033] During steps c, d, and / or e and / or for desorption, the working electrode is supplied with a negative voltage, particularly when the membrane is chemically positively charged (charged). This can be done stepwise, for example, from -10 mV to -3 volts, in order to desorb different biomolecules one after the other according to their charge, and thereby, in particular, to separate them, particularly into different second fluids or different volumes of the second fluid. However, a voltage of -3 volts can also be applied immediately to the working electrode, resulting in a short-term desorption of all adsorbed biomolecules.

[0034] For a negatively charged (charged) membrane, in particular a chemically charged one, the direct voltage in step b, in particular bI and / or b.II, is applied in such a way that the working electrode (metal coating connected to the membrane) is supplied with a negative direct voltage. This occurs, in particular, as long as an adsorption process is taking place. The adsorption process by the negatively charged (charged) membrane, in particular a chemically charged one, can also take place without a voltage supply to the working electrode, but can be enhanced by the additional voltage.

[0035] During steps c, d, and / or e and / or for desorption, the working electrode is supplied with a positive voltage. This can, for example, be applied stepwise from +10 mV to +3 volts to desorb different biomolecules one after the other according to their charge, and thereby separate them, particularly into different second fluids or different volumes of the second fluid. However, a voltage of +3 volts can also be applied immediately to the working electrode, resulting in a short-term desorption of all adsorbed biomolecules.

[0036] The coating is typically bonded to the polymer membrane and / or applied directly to it. This can be done, for example, by vapor deposition or magnetron sputtering. The thickness of the metal layer is typically between 20 nm and 50 nm, but can also be between 5 nm and 200 nm.

[0037] In particular, the polymer membrane, especially a chemically charged one, with a flat and porous metal coating is an anion or cation exchange polymer membrane.

[0038] In particular, the first fluid is passed through the membrane (filtered) between the beginning of step b and the beginning of step c. The filtration rate can be, for example, between 0.01 ml / (cm2*min*bar) and 40 ml / (cm2*min*bar). In particular, filtration is carried out for at least one second and / or step b and / or step d are each carried out for at least 1 second, in particular at least 30 seconds.

[0039] The advantage of applying the direct voltage to a, particularly chemically, positively charged (charged) membrane in such a way that the working electrode (metal coating connected to the membrane), which the fluid passes through first (upstream), is supplied with a positive direct voltage, is that the binding capacity of the charged (charged) membrane can be increased by means of this voltage which is directed in the same direction as the charge of the membrane.

[0040] The advantage of applying the DC voltage to a negatively charged (charged) membrane, particularly a chemically negatively charged one, in such a way that the working electrode (metal coating connected to the membrane), which the fluid passes through first (upstream), is supplied with a negative DC voltage, is that the binding capacity of the charged (charged) membrane can be increased by means of this voltage which is directed in the same direction as the charge of the membrane.

[0041] Preferably, the magnitude of the first and / or second DC voltage is in a range in which the fluid is not electrolytically decomposed, in particular at least 10 mV, and in particular its magnitude is in the range from 10 mV to 3 V. This is particularly advantageous for aqueous fluids. However, higher voltages of up to 50 volts can also be applied for a short time, in particular for a maximum of 3 seconds and / or at least 10 ms.

[0042] Preferably, the counter electrode is formed either by a further planar, porous coating of metal on a second side opposite the first side, wherein the planar coatings of metal are insulated from one another by the polymer membrane, or by a permeable electrode arranged with an insulating and permeable spacer in between, in particular formed by a metallic mesh.

[0043] This allows a defined and stable arrangement to be created, particularly when measuring and / or controlling the current, which minimizes external influences and can be generated reproducibly.

[0044] Metals that are difficult or impossible to oxidize are preferred for coating. Metals such as gold, platinum, or palladium are used.

[0045] Preferably, the porosity of the polymer membrane with metal coating, based on the initial bubble point pore and / or the average pore size, is reduced by between 0.01% and 10%, in particular 0.01 and 1%, compared to the uncoated polymer membrane and / or the thickness of the metal coating is 1 to 100 nm and / or the pore size of the uncoated polymer membrane is in particular in the range of 0.01 µ m and 15 µm. This enables a reliable metallic coating and a relatively small and consistent change in the physical membrane properties.

[0046] The metal is in particular precious metal, especially gold, silver and / or platinum.

[0047] The polymer membrane with a metal coating advantageously has porous passages. These can be sponge-like for polymer membranes made of polysulfone, polyethersulfone, polyamide, etc. This means that the pores are not tunnel-shaped passages, but rather the membrane has a porous structure inside and / or the wall area of ​​a passage is increased by at least a factor of 100, in particular at least a factor of 1000, compared to a tunnel-shaped passage with the same passage width. In particular, the pores located inside the membrane are at least, in particular only partially, coated with the metal coating. This allows the active surface to be increased.

[0048] The membrane, in particular a chemically charged membrane, advantageously has a binding capacity of at least 25 mg lysozyme or albumin, in particular BSA, per ml of membrane volume. This means in particular that the membrane with the metal coating on one or both sides can adsorb such an amount of the respective molecule. The membrane volume is the volume that a membrane has, whereby the volume of the pores in the membrane is part of the volume and is not subtracted. For example, a circular membrane used, such as that used in syringe filters, has a diameter of 25 mm and a thickness of 0.15 mm. This therefore has a membrane volume of 73.6 mm3. This binding capacity is advantageously present in, and in particular across, the entire pH range between pH 3 and pH 10.

[0049] The object is also achieved by a sorption and / or filtration device, in particular an electrosorption and / or electrofiltration device, comprising a, in particular chemically charged, polymer membrane with a first planar and porous metal coating on at least one side of the polymer membrane and, in particular, a metal coating contacting the coating as a working electrode. Furthermore, the device comprises a counter electrode. In particular, it comprises a second metal coating contacting the side of the membrane opposite the first coating as a counter electrode. Advantageously, it also comprises a third electrode as a reference electrode.

[0050] With regard to the coating, the counter electrode and the application of the voltages, the above applies analogously, in particular the device is set up for the corresponding application of the voltage(s), in particular it is set up to carry out the method and for this purpose has in particular a correspondingly set up control which is set up in particular to control the voltage between the electrode (also working electrode, formed by the coating of metal) and the counter electrode and / or to control the flow of the first and / or further fluid.

[0051] Advantageously, the counter electrode is formed either by a further flat, porous coating of metal on a second side opposite the first side or by a permeable electrode arranged with an insulating and permeable spacer in between, in particular formed by a metallic mesh.

[0052] Preferably, the porosity of the polymer membrane with metal coating is reduced by between 0.01% and 20%, in particular 0.01% and 1%, relative to the initial bubble point pore and / or the average pore size compared to the uncoated polymer membrane and / or the thickness of the metal coating is 5 to 100nm and / or the pore size of the uncoated polymer membrane is in particular in the range of 0.01 µm to 15 µ m.

[0053] Advantageously, the sorption and / or filtration device comprises a device for applying direct voltage to the working electrode (metal coating) in the presence of a counter electrode.

[0054] To support the adsorption of the, in particular chemically charged (charged) membrane, the direct voltage on the working electrode is directed in particular such that it is aligned with the membrane's charge. The voltage is aligned in particular if the voltage changes and / or increases the adsorption capacity and / or the zeta potential away from zero and / or if, in the case of a, in particular chemically negatively charged, membrane, the working electrode or metal coating is connected to the negative pole, and in the case of a, in particular chemically positively charged, membrane, the working electrode or metal coating is connected to the positive pole.

[0055] To desorb molecules from the, in particular chemically, charged (charged) membrane, the direct voltage on the working electrode is directed in particular such that it opposes the charge of the membrane. The voltage is oppositely directed in particular if the voltage changes the adsorption capacity and / or the zeta potential towards zero and / or reduces it and / or if, in the case of a negatively charged membrane, the working electrode is connected to the positive pole of a voltage source and, in the case of a positively charged membrane, the working electrode is connected to the negative pole. In this case, the other pole is connected in particular to the counter electrode.

[0056] Particularly preferred is an electrosorption and / or electrofiltration device in the form of a syringe attachment or syringe filter. Here, the membrane's adsorption capacity without applying a voltage is particularly advantageous. After adsorption, the attachment can then be discharged by applying a voltage, thereby desorbing the adsorbed molecules.

[0057] The membrane coated with metal on one or both sides can advantageously be processed in the same way as a conventional polymer membrane. It can be processed both as a flat membrane in syringe filters and as a pleated membrane in capsules.

[0058] In this case, the working electrode is specifically contacted, and the contact is led outward via devices such as a wire or a thin metal foil to supply a voltage. The same procedure is advantageously followed with the counter electrode, which either represents the second coating on the opposite side of the membrane or is mounted at a different location.

[0059] Such an advantageous design allows the production of syringe filters or capsules with two contacts that can be supplied with voltage from the outside.

[0060] The object is also achieved by a system comprising a sorption and / or filtration device and a desorption device, comprising a receiving device for receiving the polymer membrane with metal coating of the sorption and / or filtration device and for bringing the received polymer membrane with metal coating of the sorption and / or filtration device into contact with a first fluid, and comprising a device for applying a direct voltage between the metal coating and the counter electrode, wherein the counter electrode is either a component of the sorption and / or filtration device or of the receiving device. Desorption can be achieved simply and reliably with such a device, which in particular has means for flushing the membrane with the fluid. In particular, the device also has means for measuring at least one concentration in the fluid.

[0061] The object is also achieved by a charged polymer membrane with a flat and porous metal coating on at least a first side of the polymer membrane. Regarding the membrane and its coating(s), all advantageous embodiments described with respect to the membrane of the device or method apply accordingly.

[0062] The metal layer(s) (electrode(s)) is / are / will be applied directly to the top and / or bottom of the membrane, particularly by magnetron sputtering or metal vapor deposition. It is also possible to apply a metal layer to only one side of a membrane and place the necessary counter electrode nearby, independent of the membrane. It is also possible to implement an arrangement with three electrodes, with the first being the working electrode, the second the counter electrode, and the third the counter electrode.

[0063] The invention relates, in particular, to chemically positively and negatively charged membranes that exhibit chromatographic properties. These membranes are used for the chromatographic separation of preferably charged biomolecules. Such chemically charged membranes are generally made of polyamide, but can also be made of other polymers. Standard membranes typically have pore sizes in the range of 0.2 µ m to 0.8 µ m, but can also have pore sizes between 0.01 µ m and 10 µ m.

[0064] One possibility to achieve higher binding capacities is the use of multi-membrane stacks, typically of 2 to 10 membranes (Fa Pall, Acrodisc) and / or the application of a voltage that enhances adsorption.

[0065] In particular, the method is described as membrane chromatography with a chemically coated membrane on both sides, in which the two sides are insulated from each other and as working electrode (AE), in particular upstream side coating, and counter electrode (GE), in particular downstream side coating

[0066] The membrane consists in particular of porous polymers such as PES or PA with pore size of 0.05 to 1 um with a typical thickness of 100 to 150 µ m (range 10 to 200 µ m)

[0067] In order to adsorb negatively charged molecules in the membrane, the working electrode is set to a positive potential and the counter electrode to a negative potential.

[0068] In order to adsorb positively charged molecules in the membrane, the working electrode is set to a negative potential and the counter electrode to a positive potential.

[0069] It is assumed that the resulting electric field between the working and counter electrodes exerts additional attractive interactions on charged molecules in the region of the working electrode and repulsive interactions in the region of the counter electrode.

[0070] The binding capacity can be increased by serial arrangement of several membranes, especially 2 to 10 membranes

[0071] Typical adsorption parameters are: Transmembrane flow between 1 and 50 ml / (cm 2 < *bar*min), especially with a single-layer membrane arrangement. Advantageous potential differences between the electrode and counter electrode for adsorption are in the range of +0.1 to 30 V, especially +1 to +10 V, in the case of negative molecules. Advantageous potential differences between the electrode and counter electrode for adsorption are in the range of -0.1 to -30 V, especially -1 to -10 V, in the case of positive molecules.

[0072] The detachment and recovery of adsorbed molecules can be achieved solely by the described potential change and does not require any salinization or pH change

[0073] The desorption and elution of previously bound molecules occurs in particular after exchange of a volume of the first fluid or passage of a volume of the first fluid and / or adsorption from a volume of the first fluid, wherein the volume is less than 10 times the membrane volume, whereby the following advantageous properties can be achieved Faster recovery, i.e., shorter processing time. Less interference from diffusion processes. Higher molecular concentration than without applying a rectified voltage. The filtrate is free of interfering electrolytes (H +< , OH -< , KCl, NaCl) in higher concentrations. The process of adsorption and desorption leads to a high recovery rate of > 95% The process of adsorption and desorption can be repeated and / or by potential change alone, in particular at least 10 times, in particular at least 20 times.The described arrangement of the switchable membrane chromatography device can be used to separate molecular species with different isoelectric points. The electric field between the working electrode and counter electrode is adjusted using the DC voltage so that the attractive interaction of the stationary phase is greater for molecular species 1 than for molecular species 2, so that greater retention is achieved for molecular species 1 than for molecular species 2. Example: In the case of molecular species 1 with IEP (isoelectric point) <7 and molecular species 2 with IEP > 7, only one membrane metallized on both sides and pH 7 can be used. With a positive potential difference between the working electrode (positive) and counter electrode (negative), molecular species 1 can be bound and molecular species 2 can be eluted. With a negative potential difference between the working electrode (negative) and counter electrode (positive), molecular species 2 can be bound and molecular species 1 can be eluted.

[0074] In the adsorption phase, typical currents between working electrode and counter electrode can be measured in the range of 0.001 to 1 mA per cm 2 of membrane area, depending on analyte and electrolyte concentration, electrode DC voltage, membrane type, concentration and flow rate (feed speed).

[0075] In the desorption phase, typical currents between the working electrode and the counter electrode are particularly higher than the currents during adsorption and are in the range of -0.01 to -10 mA, depending in particular on the analyte and electrolyte concentration, electrode DC voltage, membrane type, concentration and flow rate (feed speed).

[0076] Especially at substance concentrations of more than 10E-5 mol / l, there is a correlation between the measured electrode current and the amount of adsorbed or desorbed molecules per unit time (mass transport).

[0077] The measured electrode current can therefore be used to record the amount of adsorbed or desorbed molecules. This allows the membrane loading to be controlled so that breakthrough does not occur during the adsorption phase, or the flow and / or adsorption is stopped before breakthrough. This allows the desorption phase to be designed so that flow and / or desorption is stopped when recovery is desired.

[0078] Advantageous designs are: Membrane coated on both sides with 0 to 100 nm Au and / or membrane pore size (typical pore, cut-off): 1-1000 nm and / or porosity: 10-95% and / or membrane thickness or membrane volume / effective filter area (cm): 0.005 to 0.20 cm (single membrane stack to multi-stack with n = 1 to n = 10) and / or substance concentration in the feed: 10E-10 mg / ml (endotoxins) to 10 mg / ml (proteins) and / or feed rate per cm 2 < effective filter area: 0.1 to 10 ml / (cm 2 < *min) and / or substance transport rate per cm 2 < effective filter area: 10E-11 to 100 mg / (cm 2 < *min) and / or electrolyte concentration NaCl or KaCl: 0 to 10 mmol / l and / or Stokes radius d. Analyte molecule: 1 to 20 nm and / or Molecular masses: 100 to 1,000,000 g / mol and / or Uncharged or positively charged membrane and electrode DC voltage (working electrode-counter electrode) with V > OV and / or Uncharged or negatively charged membrane and electrode DC voltage (working electrode-counter electrode) with V < OV

[0079] The described method also enables an increased binding capacity (100% to 1000%) of polymer membranes through the additive effect of the electric field between electrode and counter electrode for the cases The described method enables chromatographic separation, in particular Separation of positively charged from negatively charged molecules on positively charged membranes with a positive working electrode DC voltage, in which negatively charged molecules are adsorbed on the membrane surface and positively charged molecules are transmitted through the membrane. Separation of negatively charged from positively charged molecules on positively charged membranes with a positive working electrode DC voltage, in which positively charged molecules are adsorbed on the membrane surface and negatively charged molecules are transmitted through the membrane. Elution of the respective retained molecule type after the electrode DC voltage is reversed. Increase in separation performance (binding capacity, separation of different molecules) when several electrically switchable individual membranes are stacked in series or several individual modules are connected in series. In the case of several membranes connected in series, the option of at least two,in particular, each membrane or group of membranes shall be subjected to a different electrode DC voltage,

[0080] Compared to conventional chromatographic membranes based on ion exchange, the described method enables higher mass transfer rates (fluid volume and analyte molecule quantities per unit time and per effective membrane bed volume) by increasing the binding forces and thus the binding capacities of the effective electric field. This allows for the purification or separation of more highly concentrated drug solutions.

[0081] The invention thus enables numerous further advantages: As a result, diffusion effects play a smaller role in the occupancy of free surface binding sites than with pure ion chromatography. This means that the existing membrane pores can be filled more efficiently and in multiple layers with adsorbate molecules. This means that a membrane arrangement with one or a few stacked membranes can achieve a higher binding capacity than a comparable setup without potential control. This means that the transmembrane resistance is lower for the same binding capacity. This means that the dynamic binding capacity per membrane is closer to the static binding capacity for a given flow rate and molecule concentration than with pure ion exchange. This results in higher flow rates and shorter separation times. The measured electrode current (between working electrode and counter electrode), especially under the assumption of a highly conductive metal coating, e.g., made of gold, in particular double-sided metal coating and use of the two coatings as electrode and counter electrode, depends on the following parameters: Effective membrane area or membrane bed volume Electrode spacing Base electrolyte concentration Concentration and effective net charge of the molecules in the feed Flow rate .

[0082] The measured electrode current thus correlates with the number of adsorbed charged molecules per unit time. Thus, the current measurement in the described method enables the detection and monitoring of the remaining binding capacity. This allows for the control of the inflow with regard to the subsequent breakthrough and is particularly used. This allows for efficient and effective membrane loading. The described method enables the desorption of charged molecules. without salt concentrations (typically in the order of 1 M NaCl or KCl) without pH shift to pH < 4 for negatively and to pH > 10 for positively charged molecules The resulting filtrate with the (active ingredient) molecules contains no to low (typically 1 mmol / I NaCl or KCl or less) ions The resulting filtrate with the (active ingredient) molecules can have a moderate pH, particularly in the range 6 to 8 The described method enables concentrated release of molecules bound in the membrane, ie the elution volume is typically only a few (particularly up to 10) membrane volumes orExchange volumes, in particular by jumping from positive to negative potential (working counter electrode) for negatively charged molecules by jumping from negative to positive potential (working counter electrode) for positively charged molecules This achieves the following separation properties Short retention time after potential switch Very low recovery volume High recovery rate compared to pure ion chromatography Strong concentration, in particular 1 to 1000 times, in particular greater than 10 times, of the filtrate compared to the initial solution Desorption can be accelerated by increasing the flow rate, in particular 10 times compared to the starting flow for adsorption The measuring current between the working and counter electrode, which correlates with the desorption rate, can be used to control the .

[0083] recovery process. The described method enables the repeated adsorption and desorption of charged molecules by: No chemical regeneration of the membrane is required to restore a free membrane surface A binding capacity of > 90% of the original binding capacity and a corresponding recovery of the molecules by potential switch, which in particular occurs at least 10 times, i.e. adsorption and desorption occur in particular at least 10 times on the same membrane, in particular immediately following one another Example 1:

[0084] A commercially available chemically positively charged (charged) membrane (Membrane 1, manufacturer: Pall Corp., trade name: Mustang Membrane) was chosen for comparison with a commercially available positively charged membrane equipped with electrodes from another manufacturer (Membrane 2). Both membranes are made of polyamide and exhibit a similar binding capacity for albumin. A BSA adsorption and desorption test was conducted: Commercially available Membrane 1 achieved a binding capacity of 60 mg BSA per ml of membrane volume. Membrane 2, coated with a 40 nm gold layer on both sides, achieved a binding capacity of 100 mg BSA per ml of bed volume. The differences can be explained by the different products from different manufacturers.

[0085] The adsorbed BSA on membrane 1 was desorbed with a 1 molar salt solution. The recovery rate was between 95% and 96%.

[0086] The adsorbed BSA on membrane 2 was desorbed by applying a negative DC voltage of -3 volts to the top (upstream) of the membrane. The counter electrode was located at the bottom (downstream) of the membrane. The recovery rate was between 95% and 96%. Example 2:

[0087] An identical positively charged membrane (Membrane 1, manufacturer: Pall Corp., trade name: Mustang Membrane) was coated with a gold metal layer on both sides, and an adsorption and desorption test was conducted with albumin. A direct current of a. +2 volts and b. +3 volts was applied for adsorption. In the test with a. +2 volts, 120 mg of BSA per ml could be adsorbed, and with the direct current b. +3 volts, 161 g of BSA / ml could be adsorbed. This means that compared to Membrane 2 without a positive direct current (Example 1), 20% more BSA could be adsorbed at a direct current of +2 volts and 60% more BSA could be adsorbed at a positive direct current of +3 volts. This means that by applying an additional positive direct current to the metal layer, the binding capacity of the chemically positively charged membrane could be increased by up to 60%.

[0088] In addition, the current flow was measured during the experiments. In the experiment with a. +2 volts, a current flow of 2 mA was measured at the beginning of the adsorption of BSA. This current decreased continuously over time until breakthrough and was 0 mA when the binding capacity was reached. In the experiment with b. +3 volts, a current flow of 8 mA was measured at the beginning of the adsorption of BSA. This current flow decreased continuously over time until breakthrough and was 0 mA when the binding capacity was reached. This means that the current flow can be used as a measure of the utilization of the binding capacity. The desorption of the BSA molecules occurred in both experiments (a and b) by switching the direct voltage to -3 volts. The recovery rate of the BSA molecules was between 95% and 96%.

[0089] The examples show that biomolecules (BSA) adsorbed to a chemically positively charged membrane according to the invention can be desorbed again by applying a negative direct voltage.

[0090] Furthermore, the binding capacity of a chemically positively charged membrane can be increased by up to 60% compared to the use of a chemically positively charged membrane by additionally applying a positive direct voltage between +2 volts and +3 volts.

[0091] In addition, it was surprisingly found that the current flow between the electrodes (top and bottom of the membrane) during the adsorption of chemically positively charged membranes, which were supplied with an electrical direct voltage via the metal layer applied to the membrane, can serve as a measure of the utilization of the binding capacity and / or the remaining binding capacity.

[0092] Figure 1illustrates purely exemplary and schematically a process sequence according to the invention.

Claims

1. A method for separating at least one charged substance by means of adsorption on and electrodesorption from a polymer membrane having a first flat and porous coating of metal at least on a first side of the polymer membrane, comprising the following steps a. Preparation of the polymer membrane; b. Bringing the polymer membrane into contact with at least one first fluid, in particular in a first volume, containing said at least one charged substance and adsorbing said at least one charged substance onto the polymer membrane; c. Bringing the polymer membrane and a counter-electrode into contact with said at least one first and / or at least one second fluid, in particular in a first volume; d. Applying a first DC voltage between the first metal coating of the polymer membrane and the counter-electrode to desorb said at least one charged substance from the polymer membrane; characterised in that the polymer membrane is a chemically charged polymer membrane and in that the DC voltage is applied in the opposite direction to the charge of the polymer membrane.

2. A method according to claim 1, wherein the charged polymer membrane is an anion or cation exchange polymer membrane.

3. A method according to one of the preceding claims, characterised in that the first fluid is at least partially removed from the volume between the beginning of step b and the beginning of step d and / or in that the first fluid is at least partially passed through the polymer membrane between the beginning of step b and the beginning of step c, in particular at least 10% of the first fluid and / or at least 5 ml of the first fluid being removed or passing through and / or step b and / or step d being carried out for at least 1 second, in particular at least 30 seconds.

4. A method according to one of the preceding claims, wherein before and / or during step b a second DC voltage with polarity reversed to the first DC voltage is applied between the metal coating and a counter-electrode in contact with the first fluid, in particular over the entire duration of step b and / or at least 1 s, in particular at least 30 s.

5. A method according to one of the preceding claims, wherein the magnitude of the first and / or second DC voltage is in the range of 10mV and 3V.

6. A method according to one of the preceding claims, wherein the counter-electrode is formed either by a second flat, porous coating of metal on a second side opposite the first side, wherein the first and second flat coating of metal are insulated from each other by the polymer membrane, or by a permeable electrode, in particular formed by a metallic mesh, arranged with an insulating and permeable spacer between them.

7. A method according to one of the preceding claims, characterised in that the thickness of the first and / or second coating of metal is in the range from 5 to 200 nm, in particular from 20 and / or up to 50 nm, and / or in that the pore size of the uncoated polymer membrane is greater than 0.01 µm, in particular in the range from 0.01 µm to 15 µm, and / or the polymer membrane with coating of metal has porous passages.

8. A method according to one of the preceding claims, wherein the charged membrane has a binding capacity of at least 25 mg of lysozymes or albumin, in particular BSA, per ml of membrane volume.

9. A sorption and / or filtration device, in particular electrosorption and / or electrofiltration device, for separation via adsorption and electrodesorption, comprising a polymer membrane with a first flat and porous coating of metal on at least one side of the polymer membrane and comprising a counter-electrode and in particular a further electrode, characterised in that the polymer membrane is a chemically charged polymer membrane.

10. A sorption and / or filtration device, in particular electrosorption and / or electrofiltration device, according to claim 9, wherein the counter-electrode is formed either by a second flat, porous coating of metal on a second side opposite the first side or by a permeable electrode, in particular formed by a metallic mesh, arranged with an insulating and permeable spacer in between.

11. A sorption and / or filtration device, in particular electrosorption and / or electrofiltration device, according to one of claims 9 to 10, characterised in that the thickness of the first and / or second coating of metal is in the range from 5 to 200 nm, in particular from 20 nm and / or up to 50 nm, and the pore size of the uncoated polymer membrane is in the range from 0.01 pm to 15 µm.

12. A sorption and / or filtration device, in particular electrosorption and / or electrofiltration device, according to one of claims 9 to 11, comprising a device for applying direct voltage between the coating of metal and the counter-electrode, the direct voltage being directed in particular so as to oppose the charge of the membrane.

13. A sorption and / or filtration device, in particular electrosorption and / or electrofiltration device, according to one of claims 9 to 12, wherein the electrosorption and / or electrofiltration device is designed as a syringe attachment and / or syringe attachment filter, so that liquid moved by the syringe barrel is guided through the membrane and / or past the membrane.

14. A system consisting of a sorption and / or filtration device for separation via adsorption and a device for desorption, wherein the sorption and / or filtration device comprises a polymer membrane having a first planar and porous coating of metal on at least one side of the polymer membrane, wherein the polymer membrane is a chemically charged polymer membrane, and wherein the device for desorption comprises a counter-electrode and a receiving device for receiving the polymer membrane with metal coating of the sorption and / or filtration device and for bringing the received polymer membrane with metal coating of the sorption and / or filtration device and the counter-electrode into contact with a first fluid and a device for applying a DC voltage between the metal coating and the counter-electrode.