Abstract
Analyte electrolysis using a repetitively pulsed high voltage ion source was investigated and compared
to that using a regular, continuously operating direct current high voltage ion source in electrospray
ionization mass spectrometry. The extent of analyte electrolysis was explored as a function of the length
and frequency of the high voltage pulse using the model compound reserpine in positive ion mode.
Using +5 kV as the maximum high voltage amplitude, reserpine was oxidized to its 2, 4, 6 and 8-electron
oxidation products when direct current high voltage was employed. In contrast, when using a pulsed
high voltage, oxidation of reserpine was eliminated by employing the appropriate high voltage pulse
length and frequency. This effect was caused by inefficient mass transport of the analyte to the electrode
surface during the duration of the high voltage pulse and the subsequent relaxation of the emitter electrode/
electrolyte interface during the time period when the high voltage was turned off. This mode of ESI
source operation allows for analyte electrolysis to be quickly and simply switched on or off electronically
via a change in voltage pulse variables.
