Spectrophotometric determination of chromium(VI) by extraction of protriptylinium dichromate

Chromium(VI) (< 500 mu g dichromate) can be determined spectrophotometrically at 365 nm after its extraction as protriptylinium dichromate into acetone-chloroform (1:1, v/v). The effects of acidity, diverse ions and masking studies are reported. The relative standard deviation for determination of 200 mu g of dichromate is 0.9% (n = 7). The system has been applied to the spectrophotometric determination of chromium in steels (0.03-4%).