Direct spectrophotometric determination of chromium by microwave-oven induced flow-injection analysis Original Research Article

Two sensitive flow-injection methods have been developed for the determination of traces of Cr(VI), based on the very efficient microwave-accelerated reactions of Cr2O2−7 with dibromocarboxyarsenazo (DBM-AsA, in System 1) and dibromo-o-carborylchlorophonazo (DBOK-CPA, in System 2). The reactions are followed spectrophotometrically by measuring the decrease in the absorbance of DBM-AsA at 535 nm or DBOK-CPA at 556 nm. The sampling frequency for both systems is 40 h−1. The calibration graphs are linear in the range between 1.62 and 27.0 μg ml−1, and 0.40 and 10.80 μg ml−1 for Systems 1 and 2, respectively. The respective detection limits are 0.087 and 0.10 μg ml−1. The methods were applied to determining traces of chromium in a steel sample and electroplating solutions with satisfactory results.