SEPARATIONS OF BENZODIAZEPINES USING ELECTROCHEMICALLY MODULATED LIQUID-CHROMATOGRAPHY - EFFICIENT SEPARATIONS FROM CHANGES IN THE VOLTAGE APPLIED TO A POROUS GRAPHITIC CARBON STATIONARY-PHASE

Electrochemically modulated liquid chromatography has been applied to the separation of a mixture of benzodiazepines using a porous graphiti c carbon (PGC) stationary phase. Changes in the voltage applied (E-app l) to PGC strongly alter the retention of all of the components in the mixture, having the unusual effect of stretching both ends of the chr omatogram as E-appl becomes more negative. That is, the retention for some of the benzodiazepines increases as E-appl moves negatively, wher eas that for some of the benzodiazepines decreases. Together, these de pendencies result in the ability to resolve fully the mixture while on ly marginally increasing the total elution time with respect to that o btained at the open circuit potential. (C) 1998 Elsevier Science B.V.