Catalytic kinetic determination of trace amounts of ascorbic acid with single-sweep oscillopolarography

A highly sensitive and selective catalytic method with single-sweep d.c. oscillopolarographic detection is described for the determination of ascorbic acid, based on its activation effect on the slow vanadium(V)-catalysed reaction of BrO − 3 and methyl orange in sulphuric acid medium at 60°C. The oxidation product of methyl orange exhibits a polarographic wave at −0.40 V vs. SCE in the supporting electrolyte of sodium hydroxide, and was chosen as the indicator component for the indicator reaction. A calibration graph between 8 and 160 ng ml −1 ascorbic acid was obtained by the fixed-time procedure. The detection limit was 4 ng ml −1. Possible interferences by co-existing substances were examined.