Separations of benzodiazepines using electrochemically modulated liquid chromatography: Efficient separations from changes in the voltage applied to a porous graphitic carbon stationary phase

Abstract

Electrochemically modulated liquid chromatography has been applied to the separation of a mixture of benzodiazepines using a porous graphitic carbon (PGC) stationary phase. Changes in the voltage applied ( E appl) to PGC strongly alter the retention of all of the components in the mixture, having the unusual effect of stretching both ends of the chromatogram as E appl becomes more negative. That is, the retention for some of the benzodiazepines increases as E appl moves negatively, whereas that for some of the benzodiazepines decreases. Together, these dependencies result in the ability to resolve fully the mixture while only marginally increasing the total elution time with respect to that obtained at the open circuit potential.