Differential probe with low slope components

Abstract

1. A method for measuring an analyte in a sample, the method comprising: introducing the sample into a sample region of a measurement device, the measurement device comprising a measurement electrode and a ground electrode in contact with the sample, and a low-slope reference electrode in a reference electrode assembly having an electrolyte solution; the electrolyte solution contacting the low-slope reference electrode, the electrolyte solution being electrically coupled to the sample through at least one junction; measuring a first potential between the measurement electrode and the ground electrode; measuring a second potential between the low-slope reference electrode and the ground electrode; and determining an analyte in the sample by comparing the first potential and the second potential.

Description

[Technical field]

[0001] This application claims priority to U.S. patent application Ser. No. 17 / 569,076, entitled "DIFFERENTIAL PROBE WITH LOW-SLOPE COMPONENT," filed on January 5, 2022, the contents of which are incorporated herein by reference.

[0002] This application relates generally to potentiometric sensor-based measurements of specific ion activity or concentration in a solution, and more particularly to measurements of pH in a sample employing a low slope electrode as a component of the device. [Background technology]

[0003] Ensuring water quality is important in many industries, such as pharmaceuticals and other manufacturing sectors. In addition, ensuring water quality is important for the health and well-being of humans, animals, and plants that depend on water for survival. One water parameter that can be measured is pH, which indicates how acidic or basic the water is. Measuring pH further allows the identification or calculation of other water parameters, such as the buffering capacity of the water, the constituents of a sample, etc., and therefore allows the overall quality of the water to be identified. One method of measuring the constituents of a sample is by using a potentiometric system. Summary of the Invention [Means for solving the problem]

[0004] In summary, one embodiment provides a method for measuring an analyte in a sample, the method comprising: introducing a sample into a sample region of a measurement device, the measurement device comprising a measurement electrode and a ground electrode in contact with the sample, the electrolyte contacting the low-slope reference electrode, a low-slope reference electrode in a reference electrode assembly having an electrolyte, the electrolyte solution being electrically coupled to the sample through at least one junction; measuring a first potential between the measurement electrode and the ground electrode; measuring a second potential between the low-slope reference electrode and the ground electrode; and determining an analyte in the sample by comparing the first potential and the second potential.

[0005] Another embodiment provides an apparatus for measuring an analyte in a sample, the apparatus comprising: a measurement electrode and a ground electrode in contact with the sample; a low slope reference electrode in a reference electrode assembly having an electrolyte solution in contact with the low slope reference electrode, the electrolyte solution being electrically coupled to the sample via at least one junction; a processor; and a memory device storing instructions executable by the processor to measure a first potential between the measurement electrode and the ground electrode, measure a second potential between the low slope reference electrode and the ground electrode, and compare the first potential and the second potential to determine an analyte in the sample.

[0006] A further embodiment provides a method of measuring pH of a sample, the method including: introducing a sample into a sample region of a measurement device having a pH measurement electrode and a ground electrode in contact with the sample, and a low-slope reference electrode in a reference electrode assembly having an electrolyte solution in contact with the low-slope reference electrode, the electrolyte solution being electrically coupled to the sample through at least one salt bridge, the low-slope reference electrode having an absolute sensitivity of less than 55 mV / pH unit; measuring a first potential between the pH measurement electrode and the ground electrode; measuring a second potential between the low-slope reference electrode and the ground electrode; and determining a pH based on hydrogen ion concentration in the sample by comparing the first potential and the second potential.

[0007] The above is a summary and, as such, may contain simplifications, generalizations, and omissions of detail. Accordingly, those skilled in the art will appreciate that the summary is illustrative only and is not intended to be in any way limiting.

[0008] For a better understanding of the embodiments, together with other features and advantages, reference is made to the following: This specification should be read in conjunction with the accompanying drawings, and the scope of the present invention is set forth in the appended claims. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram of a three-electrode, differential probe for measuring an analyte in a sample. [Diagram 2] 1 is an example of data for a low slope electrode for measuring pH in a sample. [Diagram 3] FIG. 1 is a flow diagram for measuring components in an aqueous sample. [Figure 4] This is an example of a computer circuit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] It will be readily understood that the components of the embodiments, as generally described and illustrated in the figures herein, can be arranged and designed in a wide variety of different configurations in addition to the exemplary embodiments described. Thus, the following more detailed description of the examples, as illustrated in the figures, is not intended to limit the scope of the claims, but is merely representative of examples.

[0011] Throughout this specification, references to "one embodiment" or "an embodiment," or the like, mean that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment. Thus, the appearances of phrases such as "in one embodiment" or "in an embodiment" in various places throughout this specification do not necessarily all refer to the same embodiment.

[0012] Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to provide a thorough understanding of the embodiments. However, those skilled in the relevant art will appreciate that various embodiments may be modified without departing from the spirit and scope of the invention, without the need for any particular limitation or limitation of the invention, and without the need for any particular limitation or limitation of the invention, ...

[0013] In some instances, for simplicity, the terms "concentration" and "activity" may be used interchangeably, as in the case of measuring the pH of a sample with a glass-based ion selective electrode (ISE).

[0014] A common potentiometric system is the combination pH probe. Generally, such probes consist of a glass membrane-based hydrogen ion sensitive electrode used in series with a reference electrode. The glass membrane electrode is sensitive to changes in hydrogen ion activity or concentration, which can be related to the pH of the sample by a change in the electrode's voltage. The glass membrane electrode is connected in series with a reference electrode, such as a common Ag / AgCl reference electrode, to complete the probe measurement circuit. Ideally, the voltage of the reference electrode is defined by its composition and structure and is invariant with changes in the sample. In such cases, the total voltage measured between the glass membrane pH electrode and the reference electrode is a function of the voltage of the glass membrane pH electrode and the potential of the reference electrode, which is primarily due to hydrogen ion activity or concentration.

[0015] Another pH measurement probe configuration is the differential pH probe. In such devices, three main electrodes are generally utilized to measure pH (see U.S. Patents 3,709,796 and 3,862,895, incorporated herein by reference). These consist of a measurement electrode, a reference electrode, and a ground electrode. Also, like the combination electrodes described above, the measurement electrode for a differential pH probe may be a glass membrane-based electrode that is sensitive to changes in the hydrogen ion activity concentration of the sample. The reference electrode may be a common reference electrode, such as an Ag / AgCl electrode, but in differential probes it is more commonly composed of a second glass membrane-based pH electrode that is in a solution of a pH buffer electrolyte, such that the buffer electrolyte solution maintains a stable potential of the reference pH electrode. The third electrode is a ground rod, which may consist of a metal electrode, for example platinum or titanium. In a differential pH probe, the potential of the measurement electrode relative to the ground rod is compared to the potential of the reference electrode relative to the ground rod. The comparison value is related to the pH of the sample.

[0016] In both combination and differential pH probes, the accuracy of the pH measurement of a sample depends in part on the stability of the reference electrode's potential. Potential changes in the reference electrode can introduce errors into the pH measurement of a sample. One source of error can be due to reference potential drift caused by changes in the composition of the electrolyte in contact with the reference electrode. The change in electrolyte causes a shift or drift in the potential of the reference electrode and thus changes the measurement value for determining the sample pH. The degree of shift or drift depends on the nature and degree of change of the electrolyte solution, possibly caused by poisoning by sample components or dilution by the sample. The degree of shift or drift can also depend on the sensitivity of the reference electrode to the changed electrolyte solution. Reference electrodes, such as the Ag / AgCl type in combination pH probes and glass membrane-based pH electrodes used as reference electrodes in differential probes, are sensitive to the components of the electrolyte (Cl in the example of an Ag / AgCl reference electrode). - Concentration, or differential probe glass pH reference electrodes often have a potential sensitivity of about 50 to 60 mV / decade relative to hydrogen ion activity or concentration.

[0017] The invention disclosed herein describes a method to reduce errors in pH measurements due to shift or drift in the reference electrode by utilizing a reference electrode that has a low sensitivity (or slope) to the components of the reference electrolyte, such that changes in electrolyte composition, for example due to dilution or poisoning, have less impact on the accuracy error of the pH probe compared to a typical reference electrode, since the same change in electrolyte results in a smaller absolute change in the reference electrode potential.

[0018] Measurement of a sample using a potentiometric system may use a metering circuit designed to provide a relative voltage reading measured across a measurement electrode and a reference electrode. The system and method may calculate an ion concentration (hydrogen ion concentration in the case of pH metering). The voltage may be measured in a circuit including a measurement half-cell electrode and a reference half-cell electrode. The two half-cells may be electrically connected to a measurement meter or meter circuit. For example, pH may be measured using a combination of a hydrogen ion measurement half-cell and a reference half-cell electrode.

[0019] Traditionally, a reference electrode (e.g., an Ag / AgCl electrode) may be used together with the measurement electrode to form a complete cell. The reference electrode and the measurement electrode may be used to measure the concentration of an ion in a sample. In other words, the method and system may measure the pH or concentration of an ion in a sample. The reference electrode may keep its potential as constant as possible throughout the measurement. The measurement electrode may be such that the measured potential is a function of the concentration of the ion. The potential of the reference electrode may be maintained by having the reference electrode in the presence of an electrolyte solution. The electrolyte solution is, for example, a 3M KCl / AgCl(sat'd) electrolyte solution in contact with an AgCl-coated Ag wire for an Ag / AgCl reference electrode. The electrolyte is usually isolated from the sample but is in electrical contact with the external sample through a junction or salt bridge. Using the reference electrode in a circuit with the measurement electrode, the concentration of the ion in the sample can be calculated. The measurement may be the voltage of the reference electrode and the voltage of the measurement electrode, which may be displayed on a potentiometer in a millivolt (mV) instrument. The potential of a conventional two-electrode probe can be expressed as: E Cell = Emeas - (Eref + Ej) where Emeas, Eref, and Ej are the potentials of the measurement electrode, reference electrode, and junction, respectively. The reference and measurement half-cell electrodes are electrically connected to the pH meter circuit to produce a measurement in millivolts. The millivolt measurement may represent the hydrogen ion activity in the solution being measured.

[0020] The differential measurement approach utilizes a third electrode, a ground electrode. In this measurement approach, a first potential is determined between the reference electrode and the ground rod, and a second potential is determined between the measurement electrode and the ground rod. In the case of a differential pH probe, the reference electrode may consist of a standard glass electrode in a reference electrode assembly that includes a pH buffered electrolyte solution and a junction between the electrolyte solution and the sample. The overall measurement for measuring the analyte in the sample is a comparison of the first potential and the second potential. The potential of a differential probe can be expressed as: E A =E MEAS -E GRND E B =(E REF +E J )-E GRND E CELL =E A -E B =(E MEAS -E GRND )-[(E REF +E J )-E GRND )] =E MEAS -(E REF +E J ) Here, the reference half-cell electrode and ground rod are electrically connected to a pH meter circuit to produce a measurement in millivolts, and the measurement half-cell electrode and ground rod are electrically connected to a pH meter circuit to produce a measurement in millivolts. The millivolt readings from the two circuits can be used to produce a millivolt value that represents the hydrogen ion activity in the solution being measured.

[0021] Such analyte measurement systems can suffer from potential drift, which can occur due to, for example, changes in the properties of the electrolyte solution in contact with the reference half-cell electrode. Changes in the potential of the reference half-cell electrode can result in a shift in the overall system potential and therefore the voltage output. This can result in analyte measurement errors. Minimizing the drift of the reference electrode over time can improve probe accuracy over time and minimize maintenance intervals, potentially saving customers time, cost, and frustration.

[0022] Thus, the systems and methods described herein provide techniques for analyte measurement in a sample. In embodiments, the sample pH may be measured using a voltammetric or potentiometric electrode, such as an ion-selective electrode (ISE). In embodiments, the systems and methods may measure any analyte in the sample. In embodiments, the systems and methods may be used as a reference half-cell electrode, a less sensitive pH electrode, or other ion-selective electrode. Low-sensitivity electrodes, referred to as low-slope electrodes, are electrodes that are less sensitive than the sensitivity of the measurement electrode, and often have an absolute sensitivity to the analyte or other species less than 59 mV / decade, or an absolute sensitivity to changes in solution composition less than 55 mV / decade. Such low-slope reference electrodes may replace traditional reference electrode half-cells (i.e., those with a slope or sensitivity of 59 mV / decade) in electrochemical-based measurement systems. In one embodiment, a differential pH probe using a pH electrode half-cell with low sensitivity or low slope in the reference electrode assembly, e.g., a pH half-cell electrode in a reference electrode assembly with a more traditional sensitivity of ~59 mV / pH, may reduce the effect of the pH buffer electrolyte solution composition on the reference half-cell potential. This reduces the overall potential shift of the measurement system. For example, a pH reference electrode half-cell with a slope of about 59 mV / pH will produce a larger voltage shift for a unit change in pH of the reference electrolyte buffer than would be noted for a low-slope reference electrode half-cell with a sensitivity of, e.g., 6 mV / pH. Thus, for a change or drift in the electrolyte buffer, there will be a smaller change in potential, leading to a more accurate measurement of the pH (or other analyte being measured) in the sample. This approach may result in a more stable reference system and therefore a more accurate pH probe.

[0023] The illustrated embodiment examples will be best understood by referring to the drawings, in which: The following description is intended by way of example only and merely sets forth specific examples.

[0024] With reference to FIG. 1, an embodiment may measure an analyte in a sample. In an embodiment, the system and method may measure the pH of the sample. In an embodiment, the system and method may measure an ion or analyte in a sample. The system may include three electrodes: a measurement electrode, a reference electrode, and a ground electrode (ground rod). In an embodiment, when the reference electrode half-cell is in the assembly, there are one or more junctions or salt bridges in the assembly. For example, the reference electrode assembly may have a housing with the half-cell electrodes inside the housing immersed in the electrolyte. The reference electrode assembly may have one or more salt bridges or junctions. The junctions may be in the housing. The junctions may be for electrical or ionic conductivity with the sample.

[0025] In a differential measurement system such as that shown in Figure 1, a first voltage or potential measurement may be made between a measurement electrode and a ground electrode. A second potential measurement may be made between a reference electrode and a ground electrode. Note that the difference between the first and second potential measurements may be equal to the difference between the measurement electrode and the reference electrode.

[0026] In embodiments, the system and method may improve the overall performance and lifespan of a typical sensor device for measuring an analyte or pH in a sample. For ease of reading, a glass pH electrode may be used as an example. However, the system and method may relate to an electrode for measuring any analyte or ion in a sample. In other words, any ion-selective electrode (ISE) may be used.

[0027] For example, a pH glass electrode may be used as the measuring electrode. The reference electrode may be a glass electrode or a different material, such as a polymer membrane-based pH ISE. The reference electrode may be internally immersed in the electrolyte. The electrolyte of the reference assembly may be a highly conductive solution that includes a pH buffer. The buffer may maintain a pH of about 7.0. In an embodiment, there may be a single junction. In an embodiment, there may be a dual junction. The dual junction may have an electrolyte solution that does not include a pH buffer.

[0028] Within the reference housing, the electrolyte solution of the reference electrode assembly may deteriorate or change over time and with repeated use. This may result in a variation in the pH of the electrolyte of the reference electrode assembly. Such deterioration or change in the electrolyte solution of the reference electrode assembly may result in a drift in the reference electrode potential, causing inaccurate or inaccurate pH measurements.

[0029] In embodiments, the reference electrode half-cell may be selected with an ion sensitivity less than that of the measurement electrode. For example, in a system with a hydronium-sensitive glass measurement electrode (~59 mV / pH), a half-cell reference electrode with an absolute sensitivity less than about 55 mV / pH may be selected. Thus, any changes in the electrolyte solution of the reference electrode assembly will have a small effect on the value of the potential.

[0030] In a differential probe system for pH measurement, the measurement electrode and the reference electrode may be constructed of similar hydronium ion sensitive glass material. These two electrodes typically have similar hydronium ion sensitivity of ∼59 mV / pH. In such a case, a pH change of 1 pH unit in the sample or a pH change of 1 unit in the pH buffer electrolyte solution of the reference electrode assembly results in an absolute potential change of about 59 mV. In an embodiment, the lifetime and stability of the measurement system may be improved by using a less sensitive reference electrode. For example, a pH reference electrode with a sensitivity of ∼30 mV / pH or less may be used. In this way, any change in the pH of the electrolyte buffer of the reference electrode assembly can result in a smaller change in the measured potential. In other words, if a low slope electrode is used instead of the high sensitivity electrode of the reference electrode assembly, a shift or drift in the pH of the electrolyte buffer of the reference assembly will cause a smaller change to the measured potential.

[0031] In an embodiment, a glass pH measuring electrode half-cell can be combined with a calcium ISE reference electrode half-cell. The sensitivity of the calcium ISE is ∼29 mV / pCa. The sensitivity of the calcium ISE is approximately half that of a typical pH measuring electrode (∼59 mV / pH). Thus, a shift in the electrolyte solution in the reference assembly results in a smaller potential shift in the measuring potential of the probe. Thus, the accuracy of the measurement system can be improved by making the reference electrode assembly much more stable against any changes to the electrolyte buffer of the reference electrode.

[0032] In embodiments, the reference electrode half-cell may be selected based on the intended use. In this section, pH measurements are used as an example for ease of reading. However, other examples of ion selective electrodes (ISEs) sensitive to other analytes in the electrolyte solution of the reference assembly may also work for low slope reference electrode components. For example, the following ISEs may be used: Ca 2+ Ca in a solution containing ions 2+ ISE(~29mV / decade) Mg 2+ Mg in solution containing ions2+ ISE(~29mV / decade) SO4 2- SO4 in solution containing ions 2- ISE(~29mV / decade) PO4 3- PO4 in solution containing ions 3- ISE(~20mV / decade) Ba 2+ Ba in solution containing ions 2+ ISE(~29mV / decade)

[0033] In embodiments, an ISE can be used that binds interfering ions in solution with the same results while providing less sensitivity. For example, a barium ISE can be used that binds Fe 2+ (~29 mV / decade) in solution. In other words, a half-cell with a smaller sensitivity (mV / decade) than the measurement electrode can be selected.

[0034] Referring to FIG. 2, example data of the usefulness of a lower slope pH reference electrode is illustrated. A lower slope pH electrode can be used in place of a standard slope (~59 mV / pH) pH electrode. For example, a low slope pH reference electrode (~6 mV / pH slope) may shift the potential by ~3 mV for a 0.5 pH shift, compared to ~30 mV for a conventional slope pH reference electrode (~59 mV / pH slope). A low slope pH electrode may be used as the reference electrode half-cell in a reference electrode assembly. The lower slope may reduce the degree of potential shift that occurs for a unit change in the pH buffer electrolyte of the reference electrode assembly used to immerse the pH reference electrode. The potential of the reference electrode may be directly compared to the potential of the measurement electrode in a conventional two-electrode ISE probe. Here, a smaller change in the reference potential due to a change in the electrolyte composition of the reference electrode assembly may allow for more accurate measurements. In a differential arrangement (see FIG. 1), the potential of the reference pH electrode half-cell is compared to a ground rod. The reference pH electrode is immersed in the pH buffer electrolyte with an ionic junction bridging the reference electrode assembly, the pH buffer solution, and the sample, providing an electrical circuit with the reference pH electrode and the ground rod. The measurement pH electrode is in contact with the sample and may be in electrical contact with the same ground rod used in the reference pH electrode's circuit loop. The pH of the sample may be correlated to the difference between the reference pH electrode and ground rod potentials and the measurement pH electrode and ground rod potentials. Again, smaller changes in reference potential due to changes in the electrolyte composition of the pH buffer in the reference electrode assembly may allow more accurate measurements by the probe.

[0035] With reference to FIG. 3, an embodiment may measure an analyte of a sample. The analyte may be hydrogen ions to determine pH. The analyte may be any ion measured by an ISE. In an embodiment, at 301, an aqueous sample may be introduced into a sample chamber or region. The aqueous sample may be placed or introduced into the test chamber manually by a user or using mechanical means, such as gravity flow, pumps, pressure, fluid flow, etc. For example, a water sample for pH testing may be introduced into the chamber by a pump. In an embodiment, there may be one or more chambers in which one or more method steps may be performed. In an embodiment, valves or the like may control the inflow and outflow of aqueous solution, if any, into or from one or more chambers. Once the sample is introduced into the measurement system, the system may measure the pH of the sample.

[0036] In embodiments, the electrodes may be disposed completely or at least partially within a volume of the aqueous solution or sample. For example, when an aqueous solution is introduced into a chamber having one or more electrodes, the aqueous solution may at least partially cover the one or more electrodes. As another example, the one or more electrodes may be disposed partially within the chamber, with other portions of the electrodes being outside the chamber. Thus, when the aqueous solution is introduced into the chamber, it covers only the portions of the electrodes that are within the chamber.

[0037] In one embodiment, at 302, the method and system may measure a first potential between a measurement electrode and a ground electrode. At 303, the method and system may measure a second potential between a low slope reference electrode and a ground electrode. Further details are described herein.

[0038] The methods and systems may determine the analyte or analyte concentration of the sample, at 304. This determination may be made based on the first and second measured potentials.

[0039] However, if an analyte (i.e., hydrogen ions) may be measured at 304, the system may output at 305 the pH of the aqueous sample, the ion concentration of the analyte, or the like. In an embodiment, the output may be in the form of a display, storing the data in a memory device, transmitting the output via a connection or wireless system, printing the output, etc. The system may be automated, i.e., the system may automatically output the electrodes. The system may also have alarms, limits, or predefined thresholds associated with it. For example, if a measurement reaches a threshold, the system may trigger an alarm, alert the system / personnel to the fault, change the flow of the aqueous solution, etc. The data may be analyzed in real time, stored for later use, or any combination thereof.

[0040] Thus, the various embodiments described herein represent technical improvements over conventional methods and instruments for the measurement of analytes. Using the techniques described herein, the embodiments may employ methods and devices for instruments for the measurement of analytes. This is in contrast to conventional methods that have the limitations discussed above. Such techniques provide superior methods and instruments for the measurement of analytes.

[0041] While various other circuits, circuits or components may be utilized in the information processing device, one example is illustrated in FIG. 4 with respect to an instrument for analyte measurement according to any one of the various embodiments described herein. The device circuit 10' may include, for example, a measurement system on a chip design found in a particular computing platform (e.g., mobile computing, desktop computing, etc.) software and a processor are combined into one chip 11'. The processor includes an internal arithmetic unit, registers, cache memory, buses, VO ports, etc., as is well known in the art. Essentially all peripherals (12') may be connected to a single chip 11', although the internal buses, etc., are dependent on different vendors. The circuit 10' combines the processor, memory control, and I / O controller hub all into one chip 11'. Also, this type of system 10' does not typically use SATA, PCI, or LPC. For example, common interfaces include SDIO and I2C.

[0042] There is a power management chip(s) 13', for example a battery management unit BMU, that manages the power provided via a rechargeable battery 14' that can be recharged by connection to a power source (not shown). In at least one design, a single chip such as 11' is used to provide BIOS-like functionality and DRAM memory.

[0043] The system 10' typically includes one or more of a WWAN receiver 15' and a WLAN receiver 16' for connecting to various networks, such as telecommunications networks and wireless Internet devices, e.g., access points. In addition, the device 12' typically includes, e.g., transmit and receive antennas, oscillators, PLLs, etc. The system 10' includes an input / output device 17' for data input and display / rendering (e.g., a computing location located away from the single beam system that is easily accessible to the user). The system 10' typically includes various memory devices, e.g., flash memory 18' and SDRAM 19'.

[0044] The electronic components of one or more systems or devices can be understood to include, but are not limited to, at least one processing unit, memory, and a communication bus or communication means coupling various components including the memory to the processing unit(s). The system or device can include or have access to various device-readable media. The system memory can include device-readable storage media in the form of volatile and / or non-volatile memory, such as read-only memory (ROM) and / or random access memory (RAM). By way of example and not limitation, the system memory can include an operating system, application programs, other program modules, and program data. The disclosed system can be used in an embodiment of an instrument for analyte measurement.

[0045] As will be appreciated by those skilled in the art, various aspects may be embodied as a system, method, or device program product. Thus, aspects may take the form of an entirely hardware embodiment or an embodiment including software, all of which may be generally referred to herein as a "circuit," "module," or "system." Additionally, aspects may take the form of a device program product embodied in one or more device-readable medium(s) having device-readable program code embodied therein.

[0046] It should be noted that various functions described herein may be implemented using instructions stored on a device-readable storage medium, such as a non-signal storage device, and executed by a processor. In the context of this document, a storage device is not a signal, and "non-transitory" includes all media except signal media.

[0047] The program code for performing the operations may be written in any combination of one or more programming languages. The program code may be executed entirely on a single device, partially on a single device, as a standalone software package, partially on a single device, partially on another device, or entirely on other devices. In some cases, the devices may be connected via any type of connection or network, including a local area network (LAN) or a wide area network (WAN), or the connection may be through another device (e.g., via the Internet using an Internet Service Provider), via a wireless connection, e.g., near field communication, or via a hardwired connection such as a USB connection.

[0048] Example embodiments are described herein with reference to figures illustrating example methods, apparatus, and products according to various illustrative embodiments. It will be understood that operations and functionality may be implemented at least in part by program instructions. These program instructions may be provided to a processor of a device, such as a measurement device as illustrated in FIG. 1, or other programmable data processing device, to produce an instrument such that the instructions executed via the processor of the device implement the specified functions / operations.

[0049] It should be noted that values ​​provided herein should be interpreted as including equivalent values, as indicated by the use of the term "about." Equivalent values, as would be apparent to one of ordinary skill in the art, include at least values ​​obtained by ordinary rounding of the last significant figure.

[0050] This disclosure has been presented for purposes of illustration and description, but is not intended to be exhaustive or limiting. Many modifications and variations will be apparent to those skilled in the art. The exemplary embodiments are selected and described to explain the principles and practical applications, and to enable those skilled in the art to understand the disclosure of various embodiments with various modifications as appropriate for the particular use contemplated.

[0051] Thus, while illustrative embodiments have been described herein with reference to the accompanying figures, it should be understood that this description is not intended to be limiting, and that various other changes and modifications may be effected by those skilled in the art without departing from the scope or spirit of the disclosure.

Claims

1. 1. A method for measuring an analyte in a sample, comprising: Introducing a sample into a sample region of a measurement device, comprising: the measuring device having a measurement electrode and a ground electrode in contact with the sample; a low slope reference electrode in a reference electrode assembly having an electrolyte solution; the electrolyte solution contacting the low slope reference electrode, the electrolyte solution being electrically coupled to the sample via at least one junction; measuring a first electrical potential between the measurement electrode and the ground electrode; measuring a second potential between the low slope reference electrode and the ground electrode; determining an analyte in the sample by comparing the first potential to the second potential.

2. The method of claim 1 , wherein the analyte comprises a plurality of hydrogen ions.

3. The method of claim 2 , wherein the plurality of hydrogen ions is correlated to a pH of the sample.

4. 10. The method of claim 1, wherein the low slope reference electrode comprises an absolute sensitivity of less than 55 mV / pH unit.

5. 10. The method of claim 1, wherein the low slope reference electrode comprises a calcium ion selective electrode in a solution containing calcium ions.

6. 10. The method of claim 1 , wherein the low slope reference electrode comprises a magnesium ion selective electrode in a solution having magnesium ions.

7. 10. The method of claim 1, wherein the low slope reference electrode comprises a sulfate ion selective electrode in a solution containing sulfate ions.

8. 10. The method of claim 1, wherein the low slope reference electrode comprises a phosphate ion selective electrode in a solution containing phosphate ions.

9. 2. The method of claim 1, wherein the low slope reference electrode comprises a barium ion selective electrode in a solution containing barium ions.

10. 2. The method of claim 1, wherein drift of the electrolyte solution surrounding the low-slope reference electrode reduces the change in the second measured potential.

11. 1. An apparatus for measuring an analyte in a sample, comprising: a measurement electrode and a ground electrode in contact with the sample; a low-slope reference electrode in a reference electrode assembly having an electrolyte solution in contact with the low-slope reference electrode, the electrolyte solution being electrically coupled to the sample through at least one junction; A processor; a memory device storing instructions executable by the processor, measuring a first potential between the measurement electrode and the ground electrode; measuring a second potential between the low slope reference electrode and the ground electrode; and a memory device that compares the first potential to the second potential to determine an analyte in the sample.

12. The apparatus of claim 11 , wherein the analyte comprises a plurality of hydrogen ions.

13. The apparatus of claim 12 , wherein the plurality of hydrogen ions is correlated to a pH of the sample.

14. 12. The apparatus of claim 11, wherein the low slope reference electrode comprises an absolute sensitivity of less than 55 mV / pH unit.

15. 12. The apparatus of claim 11, wherein the low slope reference electrode comprises a calcium ion selective electrode in a solution containing calcium ions.

16. 12. The apparatus of claim 11, wherein the low slope reference electrode comprises a magnesium ion selective electrode in a solution containing magnesium ions.

17. 12. The apparatus of claim 11, wherein the low slope reference electrode comprises a sulfate ion selective electrode in a solution containing sulfate ions.

18. 12. The apparatus of claim 11, wherein the low slope reference electrode comprises a phosphate ion selective electrode in a solution containing phosphate ions.

19. 12. The apparatus of claim 11, wherein the low slope reference electrode comprises a barium ion selective electrode in a solution containing barium ions.

20. 1. A method for measuring the pH of a sample, comprising the steps of: Introducing a sample into a sample region of a measurement device, comprising: The measuring device has a pH measuring electrode and a ground electrode in contact with the sample; 1. A low slope reference electrode in a reference electrode assembly having an electrolyte solution, comprising: the electrolyte solution contacting the low-slope reference electrode, the electrolyte solution being electrically coupled to the sample through at least one salt bridge, the low-slope reference electrode having an absolute sensitivity of less than 55 mV / pH unit; measuring a first potential between the pH measurement electrode and the ground electrode; measuring a second potential between the low slope reference electrode and the ground electrode; determining a pH based on the hydrogen ion concentration in the sample by comparing the first potential to the second potential.

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