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(12) United States Patent (10) Patent No.: US 8,925,374 B2 Cheng Et Al

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(12) United States Patent (10) Patent No.: US 8,925,374 B2 Cheng Et Al US008.925374B2 (12) United States Patent (10) Patent No.: US 8,925,374 B2 Cheng et al. (45) Date of Patent: Jan. 6, 2015 (54) ELECTROCHEMICAL DETECTION CELL (56) References Cited FOR LIQUID CHROMATOGRAPHY SYSTEM U.S. PATENT DOCUMENTS (71) Applicants: Jun Cheng, San Jose, CA (US); Petr 4.404,065. A 9, 1983 Matson Jandik, Los Gatos, CA (US); 4497,199 A 2f1985 Matson Christopher A. Pohl, Union City, CA 4,511,659 A 4, 1985 Matson (US) 5,368,706 A 11/1994 Bowers et al. 6,387.625 B1 5, 2002 Eckhardt et al. Inventors: Jun Cheng, San Jose, CA (US); Petr 6,572,748 B1 6/2003 Herrmann et al. (72) 7,638,750 B2 12/2009 Kline Jandik, Los Gatos, CA (US); 8.342,007 B2 * 1/2013 Cheng et al. ................. T3? 61.52 Christopher A. Pohl, Union City, CA 2005, OO12543 A1 1/2005 Stearns et al. (US) 2007/0012349 A1 1/2007 Gaudiana et al. 2007/0102293 A1 5/2007 Tai et al. (73) Assignee: Dionex Corporation, Sunnyvale, CA (Continued) (US) FOREIGN PATENT DOCUMENTS (*) Notice: Subject to any disclaimer, the term of this patent is extended or adjusted under 35 JP 2002310977 10, 2002 U.S.C. 154(b) by 0 days. JP 2008058236 3, 2008 (21) Appl. No.: 13/689,885 OTHER PUBLICATIONS (22) Filed: Nov.30, 2012 “ED50A Electrochemical Detector Operator's Manual.” rev. 02, Nov. 2002, pp. 2-15 to 2-18, 5-7 to 5-18, B17 to B28, Dionex Cor (65) Prior Publication Data poration (available at http://www.dionex.com/en-us/webdocs/ US 2013/OO91936A1 Apr. 18, 2013 57752-31772 02 ED50A V17.pdf). (Continued) Related U.S. Application Data (63) Continuation of application No. 12/703,668, filed on Feb. 10, 2010, now Pat. No. 8,342,007. Primary Examiner — Hezron E Williams Assistant Examiner — Rodney T Frank (51) Int. C. GOIN 30/00 (2006.01) GOIN 27/30 (2006.01) (57) ABSTRACT GOIN 27/216 (2006.01) A detection cell for a chromatography system includes a cell GOIN30/64 (2006.01) body having an inlet, an outlet, and a counter electrode, a (52) U.S. C. working electrode, a sample flow passageway extending CPC .............. G0IN 27/30 (2013.01); G0IN 27/301 between the inlet and the outlet and in fluid contact with the (2013.01); G0IN 27/4166 (2013.01); G0IN counter and working electrodes, and a palladium/noble metal 30/64 (2013.01) reference electrode system. A method of using the detection USPC ......................................................... 73A61.52 cell is also described. (58) Field of Classification Search USPC ......................................................... 73f61.52 See application file for complete search history. 10 Claims, 3 Drawing Sheets 85 58a ( US 8,925,374 B2 Page 2 (56) References Cited Goffe et al., “Internally charged palladium hydride reference elec trode-Part 1: The effect of charging current density on long-term U.S. PATENT DOCUMENTS stability.” Medical & Biological Engineering & Computing, 1978, vol. 16, pp. 670-676. 2008. O18213.6 A1 7/2008 Arnold et al. 2008/0264148 A1 10/2008 Bulst et al. Ives et al., Reference Electrodes Theory and Practice, 1961, p. 111, 2008/02834.13 A1 11/2008 Suzuki et al. Academic Press, New York. 2009/0020438 A1 1/2009 Hodges Kelly et al., “Internally charged palladium hydride reference elec 2010/0206355 A1 8, 2010 Johnson trode: II Automatically controlled palladium hydride electrode.” Medical & Biological Engineering & Computing, 1981, vol. 19, pp. OTHER PUBLICATIONS 333-339. “PdH. Reference Electrode.” date unknown, Cormet Testing Sys Lunte et al., “Difference Mode Detection with Thin-Layer Dual tems, Helsinki, Finland (see http://www.cormet.fi/pdf PDF Pd-H2. Electrode Liquid Chromatography/Electrochemistry.” Anal. Chem. pdf). 1985, vol. 57, pp. 1541-1546. Bohs et al., “The UniJet: A New Electrochemical Detector for Munasiri et al., “Palladium-hydrogen electrodes for coulometric Microbore Liquid Chromatography.” Current Separations, 1994, vol. titration analysis of acids and bases,” J. Electroanal. Chem., 1992, 12, pp. 181-186. vol. 332, pp. 333-337. Bowers, "A new analytical cell for carbohydrate analysis with a Otterson et al., “Absorption of Hydrogen by Palladium up to Hydro maintenance-free reference electrode.” J. Pharmaceutical & Bio gen-Palladium Atom Ratios of 0.97.” 1969, p. 1-15, NASA, Wash medical Anal., 1991, vol. 9, Nos. 10-12, pp. 1133-1137. ington, DC. Dobson et al., “Plateau Potentials of the O+BPalladium Hydride Sawyer et al., “Experimental electrochemistry for chemists.” 1974, p. Electrode at Temperatures between 25 and 195° C. J. Chem. Soc., 34, Wiley, New York. Faraday Trans. 1, 1972, vol. 68, pp. 764-772. Schwing et al., “Comparison of Different Palladium-Hydrogen Elec Dobson et al., “SomeExperimental Factors which Govern the Poten trode as pH Indicators.” Analytica Chimica Acta, 1956, vol. 15, pp. tial of the Palladium Hydride Electrode at 25 to 195° C.” J. Chem. 379-388. Soc., Faraday Trans. 1, 1972, vol. 68, pp. 749-763. Stocket al., “The Palladium Electrode in Aqueous and Non-Aqueous Dobson, “The PallapHode Electrode System.” Platinum Metals Rev. Titrimetry.” Analytica Chimica Acta, 1959, vol. 20, pp. 73-78. 1981), vol. 25, No. 2, pp. 72-73. Welch et al., "Comparison of Pulsed Coulometric Detection and Fleischmann et al., “A palladium-hydrogen probe electrode for use as Potential-Sweep Pulsed Coulometric Detection for Underivatized a microreference electrode.” J. Scientific Instruments, 1968, series 2, Amino Acids in Liquid Chromatography.” Anal. Chem., 1989, vol. vol. 1, pp. 667-668. 61, pp. 555-559. Giner, J., “A Practical Reference Electrode.” Electrochem. Soc., 1964, vol. 111, p. 376. * cited by examiner U.S. Patent Jan. 6, 2015 Sheet 1 of 3 US 8,925,374 B2 s U.S. Patent Jan. 6, 2015 Sheet 2 of 3 US 8,925,374 B2 a is us in a U.S. Patent US 8,925,374 B2 US 8,925,374 B2 1. 2 ELECTROCHEMICAL DETECTION CELL electrodes can be passivated with a loss of detection sensitiv FOR LIQUID CHROMATOGRAPHY SYSTEM ity. Other types of reference electrodes such as, for example, mercury-mercurous-chloride electrodes (calomel elec BACKGROUND OF THE INVENTION trodes), mercury-mercurous Sulfate electrodes, and thallium amalgam-thallous chloride electrodes (Thalamid(R) elec 1. Field of the Invention trodes) can be affected by alkaline eluents in a similar fashion This invention relates, in general, to detection cells for and affect the functioning of the working electrodes in the liquid chromatography detection and more particularly to same way. All of the above types of reference electrodes reference electrode configurations and methods for their use. include Solutions of conductive salts enclosed in liquid junc 2. Description of Related Art 10 tions forming the interface between the solid parts of the Liquid chromatographic analysis of carbohydrates, amino electrode and the electrolyte on the outside. The liquidjunc acids and related compounds has an important place among tions are known to exude Solutions of conductive salts into the the tools utilized in biotechnology industry, biochemical electrode Surroundings. If Such electrode is positioned in a research and in clinical laboratories. Use of liquid chromato liquid stream inside a detection cell, the salts from the liquid graphic columns in combination with pulsed electrochemical 15 junction can affect functioning of another detector Such as detection in three-electrode detection cells under alkaline mass spectrometer downstream from the detection cell. If the conditions makes possible separations of unique selectivity flow through the detector cell is stopped. Such as during and direct detection without derivatization of separated ana interruptions of work during a day or overnight, the ionic lytes with unsurpassed sensitivity. Until now, the prevailing content of a liquidjunction may even contaminate the Surface approach to amperometric detection in highly alkaline mobile of the working electrode positioned upstream of the reference phases uses a gold working electrode, a platinum oratitanium electrode affecting its behavior during the Subsequent period counter electrode, and a reference electrode of the second ofuse. A gold electrode exposed to a contamination by chlo kind such as a silver-silver chloride electrode, mercury-mer ride ions exuded from a liquid junction of a reference elec curous chloride electrode, mercury-mercurous Sulfate elec trode can serve as an example. Lastly, the constant diffusion trode or thallium amalgam-thallous chloride electrode. Elec 25 of the ions from the liquidjunction predetermines the limited trodes of the second kind are electrodes in which the chemical lifetime of a reference electrode of the second kind. Its refer element (mostly metal) in the Solid phase is in equilibrium ence potential can remain in the useful range only as long as with its sparingly soluble salt placed in the liquid phase (see, the concentration of the conductive salt in the liquidjunction e.g., SAWYER et al., “Experimental electrochemistry for remains above a certain minimum value. chemists.” 1974, p. 34, Wiley, New York). Over the years, 30 Another problem with silver-silver chloride reference elec working and counter electrodes have been Subject of signifi trodes and all other reference electrodes of the second kind is cant innovations and improvements whereas there were rela the difficulty to design miniaturized detection cells with mini tively fewer improvements of the reference electrode. mal dead volume using such electrodes. Minimal dead vol With the increasing importance of capillary chromatogra ume is important for preventing peak broadening and other phy and of hyphenated detection techniques, there is a need to 35 types of peak shape deformation measured as a loss of chro miniaturize the detection cells for carbohydrate, amino acid matographic efficiency. Poor chromatographic efficiency and related compound analysis. However, miniaturization of leads among other things to poor separation between peaks cells containing a reference electrode of the second kind is and to a corresponding decrease in quantitative precision and generally very difficult due to the space requirements and accuracy of results based on the measurement of peak areas of Surface roughness of liquid junctions and because of general 40 separated compounds of interest.
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