Indirect determination of ascorbic acid with ammonium sulfate and ethanol by extraction and flotation of copper

A new method of indirect determination of ascorbic acid with ammonium sulfa te and ethanol by extraction and flotation of copper in the presence of thi ocyanate has been studied in this paper. The study shows that a small amoun t of Cu(II) is reduced to Cu(I) by ascorbic acid, then Cu(I) precipitates w ith SCN-. In the course of phase separation of ethanol from water, the prec ipitated CuSCN is extracted and stays in the interface of ethanol and water . A good linear relationship is observed between the extraction yield of Cu (II) and the amount of ascorbic acid. The detection limit for ascorbic acid is 1 x 10(-5) M. Every parameter has been optimized and the reaction mecha nism has been studied. The method is simple, rapid (5 min) and suffers from few interferences of common anions and cations. It has been successfully a pplied for the determination of ascorbic acid in pharmaceuticals and fruits .