Chemistry: electrical and wave energy – Processes and products – Electrophoresis or electro-osmosis processes and electrolyte...
Patent
1998-03-30
2000-07-11
Warden, Jill
Chemistry: electrical and wave energy
Processes and products
Electrophoresis or electro-osmosis processes and electrolyte...
204604, G01N 2726, G01N 27447
Patent
active
060867361
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
Capillary electrophoresis ("CE") and associated capillary scale technologies provide very important analytic techniques for separation and quantitation of large biomolecules. Although such techniques are useful in separating and detecting small ions, ion chromatography has been a more dominant technique. The more successful ion chromatography detection techniques have recently been found to be applicable to capillary electrophoresis. One result has been so-called suppressed conductometric capillary electrophoresis separation systems ("SuCCESS"). SuCCESS technology can produce low .mu.g/L limits of detection for a variety of small ions in a robust manner without special efforts towards pre-concentration. (See U.S. Pat. Nos. 5,358,612 and 5,433,838 to Dasgupta and Bao.)
However, capillary electrophoresis is most commonly carried out using UV-Vis absorptiometric detection, as shown in FIG. 1. (See for example, "Capillary Electrophoresis" by S. F. Y. Li, Elsevier, N.Y. 1992. As shown in FIG. 1, a CE analysis system 10 includes a separation capillary 20 whose distal tip 30 initially is in fluid communication with a solution 40 containing analyte samples A, and typically also containing other substances X. Solution 40 is retained in a source vessel 50 and is electrically coupled by an electrode 55 by a wire 57 to a power source 60 that is at a high voltage ("HV") potential V1, typically many kilovolts. A second or ground electrode 155 is often disposed in a final destination vessel 160. As shown in FIG. 1, capillary 20 passes through a UV-visible absorption detector 90 before reaching final destination vessel 160.
Coupling HV power supply 60 to capillary 20 as shown in FIG. 1 results in a left-to-right direction migration of analyte A within the capillary, as indicated by the rightward-pointing arrows. Such migration can commence within seconds of energizing power supply 60. Power supply 60 may then be turned-off, after which tip 30 of capillary 20 may be relocated into a second vessel 70 containing running electrolyte 80. Power supply 60 is coupled to solution 80 via an electrode 55, which may be identical to (or indeed the same as) electrode 55 described in conjunction with vessel 50. Power source 60 may then be re-energized, which continues the downstream migration of the sample analyte. This type of electric field induced analyte injection is termed electromigrative or electrokinetic injection ("EI").
The distal end of capillary 140 is in fluid communication with electrolyte 150 contained in a terminating electrolyte reservoir 150. Preferably electrolyte 150 is the same as running electrolyte 80, and in the embodiment shown is at ground potential.
As noted, during EI, HV is applied with the background electrolyte (BGE)-filled capillary dipped in a sample vial. In a typical situation, electroosmotic and electrophoretic movements act together to introduce the desired class of analyte ion(s) into the capillary. In general, when the electroosmotic mobility (.mu..sub.eo) is small relative to the electrophoretic mobility (.mu..sub.eo), conditions are most favorable for electromigrative preconcentration. Under these conditions a significant amount of analyte can be introduced without the concomitant introduction of a significant liquid volume. EI has been widely used for the trace analysis. This is especially valuable with UV-Vis detection because on-column UV-Vis absorption detectors, e.g., detector 90, typically used in CE provide relatively poor concentration detection limits. In the determination of small ions, where indirect detection is typically used, the situation is even less favorable than with direct detection.
In EI, when the sample ionic strength is very low, best results are obtained if a low mobility ion is deliberately added to the sample at a concentration that is high relative to the total concentration of the analyte. By "low mobility" what is meant is an ion having mobility lower than any of the analyte ions of interest. In such case, the added ion behaves like a ter
REFERENCES:
patent: 5814199 (1998-09-01), Dasgupta
M.ang.rten Jansson et al, "Micro vials or a silicon wafer for sample introduction in capillary electrophoresis" Journal of Chromatography vol. 626 pp. 310-314, 1992. No month available.
Chuzo Fujimoto, "Charged Polyacrylamide Gels for Capillary Electro Chromatographic Separations of Uncharged, Low Molecular Weight Compounds" Analytical Chemistry, vol. 67, No. 13, pp. 2050-2053, Jul. 1, 1995.
Hong-Feng Ying et al, "A Miniature Device for Electrokinetic or Hydrodynamic Sample Introduction from Small Volumes in Capillary Electrophoresis" Journal of High Resolution Chromatography, vol. 14 pp. 282-284, Apr. 1991.
Dasgupta Purnendu K.
Surowiec Kazimierz
Starsiak Jr. John S.
Texas Tech University
Warden Jill
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