The application of flow programming with pulsed amperometric detection for liquid chromatography.

A mixture of seven penicillins was separated on a C-8 column and detected using pulsed amperometric detection (PAD). Due to the polarity range of the penicillin mixture, a gradient program was necessary to produce a reasonable separation, causing some baseline shifting. Application of a flow program, where the solvent flow rate is varied within the separation, was also examined, and found to cause only a small shift in baseline response for PAD. Further examination of a variety of different flow programs was undertaken to characterize the baseline and analyte response under these conditions. Notable was that the shift in baseline from the flow program could be altered to give a shift toward either increased or decreased current, depending on the waveform and solvent combination in use. By manipulating these two parameters, one can customize the PAD response to a flow program, which may allow flow programs to be designed that only produce a minimal impact on the detector response.