Platinum Electrode System

Abstract

A detection cell for a chromatography system, the detection cell including: a cell body including a counter electrode in the form of a cell body or wire; a working electrode block including a working electrode; a gasket separating the working electrode block from the cell body, the gasket extending between an inlet and an outlet of the detection cell and defining a sample flow path in fluid contact with the cell body, the counter electrode, and the working electrode; and a reference electrode system in fluid contact with the outlet and including a platinum auxiliary electrode operably connected to a positive pole of a power source and a platinum reference electrode operably connected to a negative pole of the power source.

Description

[Technical Field]

[0001] The present invention relates generally to flow-through detection cells for chromatographic detection, and more particularly to solid reference electrodes and methods for their use in such cells. [Background technology]

[0002] Liquid chromatographic analysis of chemical compounds (eg, carbohydrates, amino acids, and related compounds) has an important place among the tools utilized in the biotechnology industry, biochemical research, and clinical laboratories.

[0003] The use of a liquid chromatography column combined with pulsed electrochemical detection in a three-electrode detection cell under alkaline conditions allows for uniquely selective separation and direct detection of separated analytes without derivatization with exceptional sensitivity.

[0004] To date, the common approach to amperometric detection in highly alkaline mobile phases has been to use a gold working electrode, a platinum or titanium counter electrode, and a liquid-type reference electrode (e.g., a silver-silver chloride electrode, a mercury-mercurous chloride electrode, a mercury-mercurous sulfate electrode, or a thallium amalgam-thallium chloride electrode).

[0005] However, silver-silver chloride reference electrodes can undergo a change in the reference potential, usually a positive shift, during their exposure to alkaline eluents used in chromatographic carbohydrate and amino acid analysis. This results in an excessive potential being applied to the working electrode, resulting in a gradually decreasing response and / or a narrowing of the linear range of the calibration plot. In extreme cases, the working electrode can become passivated with a loss of detection sensitivity.

[0006] For example, other types of reference electrodes, such as mercury-mercury chloride electrodes (calomel electrodes), mercury-mercury sulfate electrodes, and thallium amalgam-thallium chloride electrodes (Thalamid® electrodes), are affected by alkaline eluents in a similar manner and can affect the function of the working electrode in the same way.

[0007] Additionally, as capillary chromatography and multiplexed detection techniques become increasingly important, there is a need to miniaturize detection cells. More importantly, there is a need to reduce the total cell dead volume of electrochemical flow-through cells placed upstream of other detection cells. Otherwise, the electrochemical cell's dead volume will be too large, resulting in significant loss of peak efficiency in downstream detection cells.

[0008] However, miniaturization of cells containing conventional common reference electrodes, such as silver / silver chloride or similar reference electrodes, is generally very difficult due to the space requirements and surface roughness of the liquid junction, as well as the typical bulkiness of the reference electrode body. Furthermore, this type of reference electrode exhibits other problems when used in miniaturized electrochemical detection cells, such as ion leakage from the fill electrolyte solution, relatively short lifetimes, and large total cell dead volumes.

[0009] On the other hand, solid-state reference electrodes can be more easily miniaturized for use with capillary electrochemical detection cells. The total cell dead volume can be dramatically reduced, allowing the cell to be used in front of other detection cells. Furthermore, it offers several other advantages compared to silver / silver chloride reference electrodes, such as longer life, less maintenance, greater robustness, and ease of use.

[0010] More importantly, the solid-state reference electrode does not leak any ions, such as potassium and chloride, in a silver / silver chloride reference electrode. Therefore, multiple ED cells can be used in series to combine ED with different detection techniques, such as ED-MS, to develop new applications.

[0011] The use of a solid palladium-hydrogen reference electrode has been described (see, for example, U.S. Pat. No. 8,342,007). To split water, a constant DC power supply is connected to the palladium and platinum. Hydrogen gas is evolved at the palladium cathode, and oxygen gas is evolved at the platinum anode.

[0012] However, palladium has the ability to adsorb hydrogen molecules and undergoes volume expansion after absorbing hydrogen (Gileadi et al., Interfacial Electrochemistry: An Experimental Approach, Addison-Wesley, 1975, pp. 247-249), and is converted into various forms of palladium hydride.

[0013] It is known that three phases exist in palladium when hydrogen is adsorbed. 1. H:Pd atomic ratio x<0.03 (PdHx) is the α phase. 2.α / β(x:0.03~0.59). 3. β phase (x:>0.59).

[0014] As shown in Figure 1, the potential plot of a palladium hydride electrode plateaus only in the α / β phase. Therefore, palladium hydride provides the best stable potential as a reference electrode in the α / β phase (Goffe et al., "Internally Charged Palladium Hydride Reference Electrode—Part 1: The Effect of Charging Current Density on Long-Term Stability," Med. Biol. Eng., 1978, 16, 670-676).

[0015] Thus, solid-state palladium hydride reference electrodes have several inherent drawbacks. 1. It requires an excessive amount of time, over two hours, to initialize before being ready for use. 2. If used in an extremely high concentration of hydroxide, i.e. 1M NaOH, it may shorten the lifespan. 3. It increases in size after absorbing a large amount of hydrogen, and then forms palladium hydride.

[0016] It would therefore be desirable to provide a solid-state reference electrode that can overcome at least some of the problems mentioned above.

[0017] The listing or discussion of an apparently prior-published document in this specification should not necessarily be taken as an acknowledgement that the document is part of the state of the art or is common general knowledge. Summary of the Invention

[0018] Accordingly, the present invention provides a flow-through detection cell for a chromatography system, the flow-through detection cell comprising a cell body having an inlet, an outlet, and a counter electrode, a working electrode, a sample flow path extending between the inlet and outlet and in fluid contact with the counter electrode and the working electrode, and a platinum-hydrogen (Pt / H2) reference electrode system.

[0019] The detection cell may be a three-electrode detection system.

[0020] The cell body may be formed from a conductive or non-conductive material. The cell body may be formed from a corrosion-resistant metal or a conductive polymer. The cell body may be formed from a material selected from the group consisting of titanium, a corrosion-resistant alloy, stainless steel, carbon-filled polyetheretherketone (PEEK), polythiophene, polyindole, and polynaphthalene.

[0021] The reference electrode system is a Pt / H2 reference electrode system. The reference electrode system includes a platinum (Pt) reference electrode and a platinum (Pt) auxiliary electrode, both of which are in fluid contact with the fluid sample flow path. The reference electrode may be connected directly or indirectly to the negative pole of a power source. The auxiliary electrode may be connected directly or indirectly to the positive pole of the power source.

[0022] The detection cell may further include a gasket disposed between the counter electrode and the working electrode and having a notch that forms a laminar channel between the counter electrode and the working electrode, the channel being fluidly connected to the inlet and outlet of the cell body, thereby forming a portion of the fluid sample passageway.

[0023] The cell body may include an inlet and an electrode cavity fluidly connected to the inlet and outlet, thereby forming a portion of the fluid sample flow path. At least one of the Pt reference electrode and the Pt auxiliary electrode may be a wire. For example, a platinum (Pt) reference electrode may include a wire extending into a reference electrode bore in the cell body that is insulated with a non-conductor, such as a polymer tubing.

[0024] Another aspect of the present invention relates to a chromatography system including any of the above detection cells. The chromatography system may include multiple detection cells, and the detection cells may be arranged in series. [Brief explanation of the drawings]

[0025] The method and apparatus of the present invention have other features and advantages that will be apparent from, or will be more fully described in, the accompanying drawings incorporated herein and the following detailed description of the invention, which together serve to explain certain principles of the invention.

[0026] The invention will now be illustrated, but not limited to, by reference to the following figures and examples.

[0027] [Figure 1] 1 is a potential plot of a palladium hydride electrode. [Figure 2] FIG. 1 is a side view of a thin layer detection cell fitted with a solid-state true Pt / H2 reference electrode. [Figure 3] FIG. 1 is a side view of an ED cell with a Pt / H2 reference electrode in the working electrode block. [Figure 4] FIG. 1 is a side view of a cell with a Pt / H2 reference electrode in the counter electrode block. [Figure 5]FIG. 1 is a schematic diagram of an exemplary detection cell for a chromatography system according to various aspects of the present invention. [Figure 6] Overlay chromatograms obtained using the new Pt / H2 and Ag / AgCl REs in the current ED cell: a mixture of six monosaccharides. [Figure 7A] Overlaid 40 consecutive chromatograms obtained using an Ag / AgCl reference electrode. [Figure 7B] Overlaid 40 consecutive chromatograms obtained using a Pt / H2 reference electrode. [Figure 8A] Response stability plot of 40 consecutive injections obtained with an Ag / AgCl reference electrode. [Figure 8B] Response stability plot of 40 consecutive injections obtained using a Pt / H2 reference electrode. [Figure 9] Overlay chromatograms obtained using a new Pt / H2 reference electrode in a flow-through ED cell for the analysis of fluorodeoxyglucose (FDG), fluorodeoxymannose (FDM), and chlorodeoxyglucose (CDG): 0.5 ppm (solid line), 5 ppm (dotted line), and 50 ppm (dashed line). [Figure 10] Typical chromatogram obtained with a new Pt / H2 reference electrode in a flow-through ED cell for the analysis of streptomycin: 1. system suitability peak (thermal decomposition peak of streptomycin), 2. streptomycin. [Figure 11] Typical chromatogram obtained with the new Pt / H2 reference electrode in a flow-through ED cell for the analysis of a mixture of mono- and disaccharides: 1. glucose, 2. fructose, and 3. sucrose. [Figure 12]Typical chromatogram obtained with a new Pt / H2 reference electrode in a flow-through ED cell for the analysis of a mixture of seven alcohols: 1. arginine, 2. lysine, 3. alanine, 4. threonine, 5. glycine, 6. valine, 7. serine, 8. proline, 9. isoleucine, 10. leucine, 11. methionine, 12. histidine, 13. phenylalanine, 14. glutamate, 15. aspartate, 16. cystine, 17. tyrosine, (*: system peak). [Figure 13] Typical chromatogram obtained with a new Pt / H2 reference electrode in a flow-through ED cell for the analysis of a mixture of seven alcohols: 1. sorbitol, 2. glycerol, 3. ethylene glycol, 4. methanol, 5. ethanol, 6. 1-propranolol, and 7. 1-butanol (50 ppm excluding 100 ppm 1-butanol) (*: excluded volume). DETAILED DESCRIPTION OF THE INVENTION

[0028] Reference will now be made in detail to various embodiments of the invention, examples of which are illustrated in the accompanying drawings and described below. While the invention will be described in conjunction with exemplary embodiments, it should be understood that this description is not intended to limit the invention to those exemplary embodiments. On the contrary, the invention is intended to encompass not only the exemplary embodiments but also various alternatives, modifications, equivalents, and other embodiments that may be included within the invention as defined by the appended claims.

[0029] FIG. 2 illustrates an exemplary embodiment of the present invention in which the Pt / H2 reference electrode is part of a three-electrode thin layer detection cell.

[0030] A detection cell typically contains three electrodes. However, a detection cell may have two or more electrodes according to various embodiments, configurations, and design considerations. While older two-electrode designs use the same two electrodes (working and reference electrodes) for voltage regulation and current measurement, in three-electrode cells, only the voltage is regulated between the reference and working electrodes. Current measurement is performed between the working and counter electrodes.

[0031] The counter electrode is sometimes called an auxiliary electrode. However, in the context of this specification, the term auxiliary electrode is reserved for the second anodic electrode of a two-electrode system of a Pt / H2 electrode. There are reports describing chromatographic detection cells with more than three electrodes, for example, including multiple working electrodes referenced to the same reference electrode (LUNTE et al., "Difference Mode Detection with Thin-Layer Dual-Electrode Liquid Chromatography / Electrochemistry," Anal. Chem., 1985, Vol. 57, pp. 1541-1546). The Pt / H2 electrode described here can be used with all of the above types of low-dead-volume chromatographic detection cells.

[0032] The detection cell of the present invention eliminates the need for a large reference electrode compartment required when utilizing a silver / silver chloride electrode. As shown in FIG. 2, the relatively bulky silver / silver chloride reference electrode is replaced by a Pt wire (3) connected to the negative pole (5) of a secondary power supply. Preferably, a positively charged electrode consisting of a Pt wire (2) is required to complete the reference electrode system (Pt / Pt charged by a secondary DC power supply). The two Pt wires are insulated from each other and from the counter electrode block (10) via a polymer sleeve. The novel solid-state reference electrode is located in the same laminar flow channel as the working electrode (6) and counter electrode (10). The flow channel (11) is defined by cutouts in the thin film gaskets (9) and (9b).

[0033] The Pt reference electrode (3) and / or auxiliary Pt electrode (2) may preferably be in the form of a Pt wire, although the Pt reference electrode (3) and / or auxiliary Pt electrode (2) may also be in the form of a foil or tube.

[0034] Typically, the detection cell also includes a yoke-knob assembly (not shown) for assembly of the detection cell.

[0035] Suitable materials for the cell body (10), which functions as a counter electrode, include, but are not limited to, titanium, high-quality stainless steel, or a sturdy, highly conductive polymer. Suitable materials for the cell body, which does not function as a counter electrode, include, but are not limited to, polytetrafluoroethylene (PTFE), polyetheretherketone (PEEK), polychlorotrifluoroethylene (Kel-F), and polycarbonate. The cell body is preferably machined or otherwise formed to include an inlet (7) and an outlet (1) that are fluidly connected to the laminar channel (11) to form a fluid sample flow line. Preferably, the inlet, channel, and outlet are configured to minimize dead volume within the detection cell. In the illustrated configuration, the laminar pathway of the cell is formed by a channel in the gasket; however, it will be understood that the laminar pathway of the cell could also be formed by a microgroove machined into the body of the conductive counter electrode.

[0036] For purposes of the present invention, a thin-layer channel has a volume ranging from about 1 pL to about 100 μL, e.g., from about 1 pL to 1 μL. The following ranges of channel dimensions, either in a gasket or as micromachined microgrooves, can be used to form low-volume thin-layer channels: The overall dimensions of the channel may include a width of about 0.01 mm to about 6 mm, e.g., about 0.1 to about 3 mm, a length of about 3 mm to about 24 mm, e.g., about 6 to about 12 mm, and a thickness of about 0.001 mm to about 1.0 mm, e.g., about 0.0125 to about 0.5 mm. Preferably, they include a width of about 0.5 to 2 mm, a length of about 6 to 10 mm, and a thickness of about 0.0125 to 0.25 mm. Most preferably, they include a width of about 0.5 to 1.5 mm, a length of about 6 to 9 mm, and a thickness of about 0.0125 to 0.05 mm.

[0037] The yoke-knob assembly allows for rapid assembly and disassembly of the detection cell in an otherwise known manner. In particular, the yoke-knob assembly includes a yoke for aligning the working electrode (6) with the gasket (9) and, in turn, with the cell body (10) to sealingly engage the working electrode, gasket, and cell body with one another. It will be appreciated that the yoke-knob assembly can be configured to provide a consistent sealing force against the working electrode, e.g., approximately 1-15 lb / in² of pressure, to suitably and reliably maintain the sealing action of the gasket against both the working electrode and the cell body.

[0038] As previously mentioned, in contrast to conventional detectors which include a relatively bulky silver / silver chloride reference electrode, the detection cell of the present invention includes a platinum / platinum (Pt / Pt) reference electrode system.

[0039] In Figure 2, a platinum (Pt) hydrogen reference electrode system (2, 3) extends into the reference electrode bore of the conductive cell body (10, counter electrode) insulated with a polymer tubing (14). The reference electrode (3) is connected directly or indirectly to the negative pole (5) of a suitable power supply.

[0040] As detailed above, the reference electrode system includes an auxiliary Pt electrode (2) to complete the reference electrode system (2, 3), which is positively charged by being connected directly or indirectly to the positive pole (4) of a suitable power supply.

[0041] In operation and use, the detection cell is used in a manner similar to that of known detectors having a conventional silver / silver chloride reference electrode. For example, the Pt reference electrode (3) and the Pt auxiliary electrode (2) are connected to a power supply with the polarity shown in FIG. 2. Furthermore, the Pt reference electrode (3) is connected as a reference electrode to the electronic circuitry of the three-electrode detection system in an otherwise conventional manner. In a preferred configuration, the auxiliary electrode (2) is positioned downstream of the working electrode (6) and the Pt reference electrode (3), and the Pt reference electrode (3) is positioned downstream of the working electrode (6).

[0042] The Pt / H2 reference electrode is generated by applying a potential from a power supply connected to the Pt reference electrode (3) and the Pt auxiliary electrode (2). Preferably, the potential is less than approximately 10 V, more preferably approximately 1.25-2 V, and most preferably approximately 1.5-1.7 V. The potential is also substantially constant, i.e., subject to voltage oscillations and / or other fluctuations of less than approximately 10 mV, more preferably less than approximately 0.1 mV, and most preferably less than approximately 0.001 mV.

[0043] The Pt reference electrode provides a hydrogen electrode that provides a stable reference potential relative to the Ag / AgCl and Pt / H2 reference electrodes immersed in the same solution.

[0044] The actual difference in the reference values ​​can be measured using any one of a variety of suitable methods. For example, for any new detection experiment, the precisely adjusted values ​​of the DC amperometric potential and pulsed electrochemical potential can be determined by achieving approximately the same level of baseline signal and similar peak area as a silver / silver chloride reference electrode. Alternatively, the reference potential of a Pt / H2 reference electrode can be evaluated by potential measurements compared to a conventional silver / silver chloride electrode installed in a second detection cell located downstream of the first detection cell.

[0045] Alternatively, the Pt / H2 reference electrode can be located in the working electrode block (8) instead, which differs from the design shown in Figure 2 (see Figure 3). The advantage of this design is that the Pt / H2 reference electrode can be regenerated by polishing it together with the working electrode, thereby extending the life of the reference electrode.

[0046] Finally, the Pt / H2 reference electrode may be implemented as a reference electrode module containing two closely spaced Pt wires (see Figure 4). The two Pt wires are inserted into the same polymer tube (12), such as a double-lumen tube with a double bore, while remaining insulated from each other. Such a reference electrode module can be fabricated to fit the counter electrode and flushed together with the counter electrode body in a flow-through electrochemical cell. The reference electrode is sufficiently insulated from the counter electrode (10). This compact configuration of the Pt / H2 reference electrode allows for a shorter length of the thin-layer flow channel 11. As a result, the total cell dead volume of the flow-through cell is further minimized, potentially preventing degradation of chromatographic performance in downstream detectors.

[0047] Advantageously, the present invention provides a Pt / H2 reference electrode that can be easily miniaturized for use in chromatographic detection cells. The present invention also makes the Pt / H2 reference electrode suitable for use in capillary systems that have extreme requirements for minimizing dead volume.

[0048] The reference electrode system of the present invention produces a stable reference potential that does not change upon exposure to the eluent or mobile phase used in the chromatographic separation process. Furthermore, the reference electrode assembly of the present invention does not leach any ions that would interfere with the proper functioning of other detectors connected downstream.

[0049] The configuration of the reference electrode assembly of the present invention allows for a stable reference potential during long-term exposure to alkaline column eluates. Advantageously, there is no accidental application of excessive detection potential to the working electrode, which would result in a downward trend in detection response over time or a narrower range of linearity in the calibration plot.

[0050] Because the Pt / H2 reference electrode does not include a liquid junction like a typical liquid-type reference electrode, there is no electrolyte exiting the reference electrode (e.g., chloride ions exiting a silver / silver chloride electrode). In general, the reference electrode assembly of the present invention provides a longer service life compared to conventional silver / silver chloride reference electrodes and other liquid-type reference electrodes.

[0051] The Pt / H2 reference electrode can be realized as a reference electrode assembly including a Pt reference electrode (3) and a Pt auxiliary electrode (2), each in the form of a wire in close proximity to one another. Such a reference electrode system can be fabricated to fit into existing reference electrode compartments designed for conventional silver / silver chloride reference electrodes.

[0052] For example, the reference electrode system may be configured to replace the large reference electrode cylinder of an existing detection cell, such as the ED provided by Thermo Fisher Scientific, Inc., Waltham, Massachusetts, and shown in the ICS-6000 and other ICS series Ion Chromatography System Operator's Manual (Dionex ICS-6000 Ion Chromatography System Operator's Manual, Document No. 22181-97002, Revision 01, February 2018), the entire contents of which are incorporated herein by reference.

[0053] In another exemplary embodiment of the invention illustrated in Figure 5, a detection cell includes a cell body (10) having a threaded reference electrode cavity (14), a working electrode block (8, Figure 4), and a gasket (9, Figure 4) disposed between the cell body and the working electrode block. An inlet (7) is fluidly connected to the bottom of the threaded reference electrode cavity. The detection cell may also include a reference electrode housing that is secured within the threaded reference electrode cavity to position the end of the electrode in electrical contact with the fluid sample line.

[0054] The reference electrode housing may be secured within cavity 14 by a tightening nut 11, which allows for releasably securing the reference electrode housing within cell body 10. It will be appreciated that the electrode housing may be releasably or permanently secured within the cavity by other suitable means, including, but not limited to, a gasket, a press fit, a bayonet fit or cap, welding, etc.

[0055] Suitable fixtures may secure the Pt reference electrode (3) and Pt auxiliary electrode (2) within the housing. For example, 6-32 fittings and 1 / 16 inch tubing may be utilized to hermetically secure the wire electrodes within the housing. It will be appreciated that suitable means, such as a wire sleeve, may be utilized to secure the electrodes within the reference electrode housing. It will also be appreciated that the electrodes may be formed from wire or other suitable conductors, such as rod, tube, foil, net, or grid-shaped conductors.

[0056] A reference electrode gasket (13) may be provided, defining a laminar channel extending between the Pt reference electrode (3) and the Pt auxiliary electrode (2). Similar to the gasket (9, FIG. 4) described above, the laminar passage through the cell by the reference electrode may be formed by a channel in the reference electrode gasket, or by microgrooves machined into the reference electrode cavity (14) and / or the conductive counter electrode cell body (10). In either case, the channel and outlet are configured to minimize dead volume within the detection cell.

[0057] The foregoing description of specific exemplary embodiments of the present invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and obviously, many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and their practical applications, thereby enabling those skilled in the art to make and utilize various exemplary embodiments of the invention, and various alternatives and modifications thereof. It is intended that the scope of the present invention be defined by the appended claims and their equivalents.

[0058] For the avoidance of doubt, when the terms "comprising" or "comprises" are used herein, the detection cell or detection system being described must include the recited components, but may optionally include additional components. "Comprising" should be considered to include the terms "consisting of" or "consists of" when the detection cell or system being described must contain only the recited components.

[0059] For the avoidance of doubt, preferences, options, particular features, etc. stated with respect to a given aspect, feature or parameter of the invention should be deemed to be disclosed in combination with any and all other preferences, options, particular features, etc. stated with respect to the same or other aspects, features and parameters of the invention, unless the context indicates otherwise.

[0060] As used herein, the term "about," for example, when referring to a measurable value (such as an amount or parameter), refers to a variation of ±20%, ±10%, ±5%, ±1%, ±0.5%, or particularly ±0.1% of the specified amount.

[0061] Example The equipment used in the following experiments was obtained from Thermofisher Scientific as indicated in the table and detailed information can be found in the relevant product catalogue.

[0062] Examples obtained using a prototype reference electrode on a current ED cell Example 1: Analysis of a mixture of six monosaccharides All chromatograms were obtained using the ICS-5000 under the conditions and cell embodiment in Table 1 (Figure 5). + Data illustrating the performance of the new Pt / H2 reference electrode installed in the reference compartment of a current flow-through electrochemical cell for chromatographic detection are shown in Figures 6, 7A, 7B, 8A, and 8B and in Table 2.

[0063] [Table 1] *System control and data processing: Thermo Scientific Dionex Chromeleon® 7.2 software

[0064] [Table 2] *: Ratio = response of prototype RE / response of Ag / AgCl RE **:n=3

[0065] Example 2: Analysis of Fluorodeoxyglucose (FDG), Fluorodeoxymannose (FDM) and Chlorodeoxyglucose (CDG) Chromatograms were generated on an ICS-6000+ system using the conditions and cell embodiment (Figure 5) in Table 3. A chromatogram illustrating the performance of the new Pt / H2 reference electrode installed in the reference compartment of the current flow-through electrochemical cell for chromatographic detection is shown in Figure 9.

[0066] [Table 3] *System control and data processing: Thermo Scientific Dionex Chromeleon® 7.2 software

[0067] Example 3: Analysis of streptomycin Chromatograms were generated on an ICS-6000 system using the conditions and cell embodiment (Figure 2) in Table 4. A chromatogram illustrating the performance of the new Pt / H2 reference electrode installed in the reference compartment of the current flow-through electrochemical cell for chromatographic detection is shown in Figure 10.

[0068] [Table 4] *System control and data processing: Thermo Scientific Dionex Chromeleon® 7.2 software

[0069] Example 4: Analysis of mixtures of monosaccharides and disaccharides Chromatograms were generated on an ICS-6000 system using the conditions and cell embodiment (Figure 2) in Table 5. A chromatogram illustrating the performance of the new Pt / H2 reference electrode installed in the reference compartment of a current flow-through electrochemical cell for chromatographic detection is shown in Figure 11.

[0070] [Table 5] *System control and data processing: Thermo Scientific Dionex Chromeleon® 7.2 software

[0071] Example 5: Analysis of 17 amino acids Chromatograms were generated on an ICS-6000 system using the conditions and cell embodiment (FIG. 5) in Table 6. A chromatogram illustrating the performance of the new Pt / H2 reference electrode installed in the reference compartment of a current flow-through electrochemical cell for chromatographic detection is shown in FIG.

[0072] [Table 6] *System control and data processing: Thermo Scientific Dionex Chromeleon® 7.2 software

[0073] Example 6: Analysis of a mixture of seven alcohols Chromatograms were generated on an ICS-6000 system using the conditions and cell embodiment (FIG. 5) in Table 7. A chromatogram illustrating the performance of the new Pt / H2 reference electrode installed in the reference compartment of a current flow-through electrochemical cell for chromatographic detection is shown in FIG.

[0074] [Table 7] *System control and data processing: Thermo Scientific Dionex Chromeleon® 7.2 software

Claims

1. 1. A detection cell for a chromatography system, the detection cell comprising: a cell body including a counter electrode in the form of a cell body or wire; a working electrode block including a working electrode; a gasket separating the working electrode block from the cell body, the gasket extending between an inlet and an outlet of the detection cell and defining a sample flow path in fluid contact with the cell body, the counter electrode, and the working electrode; a reference electrode system comprising a platinum auxiliary electrode in fluid contact with the outlet and operably connected to a positive terminal of a power source, and a platinum reference electrode operably connected to a negative terminal of the power source.

2. The detection cell of claim 1 , wherein the detection cell is a three-electrode detection system.

3. The detection cell of claim 1 , wherein the cell body is formed from a conductive or non-conductive material.

4. 10. The detection cell of claim 1, wherein the cell body is formed from a corrosion-resistant metal or a conductive polymer and a non-conductive polymer.

5. 5. The detection cell of claim 4, wherein the cell body is formed from a conductive material selected from the group consisting of titanium, a corrosion-resistant alloy, stainless steel, carbon-filled polyetheretherketone (PEEK), polythiophene, polyindole, and polynaphthalene, and a non-conductive material selected from the group consisting of polytetrafluoroethylene (PTFE), polyetheretherketone (PEEK), polychlorotrifluoroethylene (Kel-F), and polycarbonate.

6. The detection cell of claim 1 , wherein the reference electrode system comprises a solid reference electrode.

7. 10. The detection cell of claim 1, wherein the platinum reference electrode and the platinum auxiliary electrode are in electrical contact with a fluid sample passageway.

8. 8. The detection cell of claim 7, wherein the platinum reference electrode comprises a wire extending into a reference electrode bore in the cell body.

9. 10. The detection cell of claim 1, wherein the cell body includes an electrode cavity fluidly connected to the inlet and the outlet, thereby forming a portion of a fluid sample passageway.

10. 10. The detection cell of claim 9, wherein at least one of the platinum reference electrode and the platinum auxiliary electrode is a wire.

11. A chromatography system comprising the detection cell of claim 1.

12. A chromatography system comprising the detection cell of claim 9.

13. A chromatography system comprising a plurality of the detection cells according to claim 1, the detection cells being arranged in series.

14. 1. A detection cell for a chromatography system, the detection cell comprising: A cell body; a working electrode block including a working electrode; a sample channel extending between the inlet and outlet of the detection cell and in fluid contact with the cell body and the working electrode; a counter electrode in fluid contact with the sample channel; an auxiliary electrode in fluid contact with the outlet and operably connected to the positive terminal of a power source; and a Pt / H ２ a detection cell including a reference electrode system including a reference electrode;

15. The detection cell of claim 14 , wherein the cell body is formed from a conductive material.

16. Said Pt / H ２ 15. The detection cell of claim 14, wherein a reference electrode and the auxiliary electrode are in electrical contact with the sample channel, and the auxiliary electrode comprises a platinum electrode.

17. Said Pt / H ２ 15. The detection cell of claim 14, wherein the reference electrode comprises a wire extending into a reference electrode bore in the cell body.

18. 15. The detection cell of claim 14, wherein the reference electrode system operates at a potential of less than approximately 10 V, subject to a voltage fluctuation of less than approximately 10 mV.

19. The detection cell of claim 14, wherein the sample channel has a volume of approximately 1 pL to 100 μL.

Images