Non-aqueous capillary electrophoresis with electrochemical detection

The application of electrochemical detection (ED) in conjunction with non-aqueous capillary electrophoresis (CE) is described. Using an acetonitrile-based buffer system only minor effects of the high voltage on the electrochemical detection circuit occur during CE experiments. Thus, for the first time CE-ED measurements are performed employing 75-mu m I.D. capillaries without a special capillary modification or interruption. Capillaries from various sources are evaluated regarding their suitability for non-aqueous CE-ED. All fused-silica capillaries tested allow reproducible measurements. However, there are differences in separation efficiency depending on the fused-silica material used. The analytical characteristics of non-aqueous CE-ED are explored using ferrocene and (ferrocenylmethyl)trimethyl ammonium perchlorate ([FcMTMA]ClO4) as model analytes. The reproducibility of migration time and signal height is expressed by relative standard deviations of 0.18 and 1%, respectively (n = 10). The limit of detection for [FcMTMA]ClO4 is 6 x 10(-8) M. Practical applications concerning the determination of dye compounds such as malachite green, crystal violet and rhodamine B are discussed. A remarkably good stability of electrode response is observed for extended measuring periods owing to the well-defined surface characteristics of the platinum electrode in the acetonitrile-based medium. (C) 1998 Elsevier Science B.V.