Rapid determination of chromium(VI) in electroplating waste water by use of a spectrophotometric flow injection system

A new rapid and sensitive FI method is reported for spectrophotometric determination of trace chromium(VI) in electroplating waste water. The method is based on the reaction of Cr(VI) with sodium diphenylamine sulfonate (DPH) in acidic medium to form a purple complex (λmax = 550 nm). Under the optimized conditions, the calibration curve is linear in the range 0.04–3.8 μg m l−1 at a sampling rate of 30 h−1. The detection limit of the method is 0.0217 μg m l−1, and the relative standard deviation is 1.1% for eight determinations of 2 μg ml−1 Cr(VI). The proposed method was applied to the determination of chromium in electroplating waste water with satisfactory results.