CONTROLLED POTENTIAL COULOMETRY WITH THE FLOW-THROUGH RETICULATED VITREOUS CARBON ELECTRODE

Microgram and submicrogram amounts of ferricyanide ion, catechol, hydroquinone, ascorbic acid in vitamin C tablets, and epinephrine have been determined by controlled potential coulometry in flowing streams. Sample solutions ranging from 2 to 50 mL in volume were added to a stream of supporting electrolyte and carried through the RVC electrode (void volume = 7.8 mL) at flow rates from 0.6 to 3 mL/min by a gravity flow system. Complete electrolysis occurred in about 250 s and replicate determinations were run every 4 to 6 min. The background current is constant, independent of flow rate and time of electrolysis, and therefore was nulled out prior to integration of the Faradaic current. The Faradaic current-time integral is independent of temperature and fluctuations in the flow rate. The background noise on the current signal corresponded to 1.4 ng of material assuming an equivalent weight of 100 and an electrolysis time of 250 s. In many instances, results were accurate and precise to 5 ppt relative. © 1979, American Chemical Society. All rights reserved.