Indirect determination of thiocyanate with ammonium sulfate and ethanol by extraction–flotation of copper

Abstract

A new method for the indirect determination of thiocyanate with ammonium sulfate and ethanol by extraction–flotation of copper in the presence of ascorbic acid is described. A small amount of Cu(II) is reduced to Cu(I) by ascorbic acid, then Cu(I) is precipitated with SCN⁻. In the course of phase separation of ethanol from water, the precipitated CuSCN stays in the interface of ethanol and water. A good linear relationship is observed between the flotation yield of Cu(II) and the amount of SCN⁻. Using 1.0 ml of 1 × 10⁻³ M ascorbic acid solution, 50 μg of Cu(II), 3.5 g of (NH₄)₂SO₄ and 3.0 ml of ethanol with a total volume of 10 ml, the concentration of thiocyanate could then be determined by determining the flotation yield of Cu(II). The detection limit for thiocyanate is 5 × 10⁻⁵ M. Every parameter was optimized and the reaction mechanism was studied. The method is simple and rapid and it was successfully applied to the determination of thiocyanate in urine and saliva of smokers and non-smokers and in venous blood of patients infused with sodium nitroprusside.