Factors Affecting Quantitative Electrokinetic Injections from Submicroliter Conductive Vials in Capillary Electrophoresis

• Published in: Analytical chemistry (Washington) 1999-09, Vol.71 (18), p.4014-4022
• Main Authors: Fuller, Robert R, Sweedler, Jonathan V
• Format: Article
• Language: English
• Subjects: Analytical chemistry; Chemistry; Chromatographic methods and physical methods associated with chromatography; Electrophoresis, Capillary - instrumentation; Electrophoresis, Capillary - methods; Exact sciences and technology; Kinetics; Microchemistry - instrumentation; Microchemistry - methods; Other chromatographic methods
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/ac990116h

The factors influencing quantitative electrokinetic injections in capillary electrophoresis for custom 340-nL, 10̄-μL, and 110-μL stainless steel sample vials have been investigated using a six-analyte mixture containing catecholamines and indolamines. Deleterious sample degradation is increased with smaller sampling vials, decreased capillary−electrode distances, and increased current passed during the injection. Zero-voltage injections from the smallest vials also demonstrate additional injection discrepancies when compared to larger-volume bulk solution injections. These effects are in addition to the electrokinetic bias and complicate the selection of appropriate internal standards. For nanoliter-volume conductive vials, the injection process creates new species and eliminates other electroactive species to such an extent that quantitation becomes problematic.