Spectrophotometric reaction rate method for the determination of ultratrace amounts of rhodium by its catalytic effect on the oxidation of Nile Blue by periodate

A selective spectrophotometric method is proposed for the determination of ultratrace amounts of Rh(III). The proposed method is based on the catalyti c effect of Rh(III) on the oxidation of Nile Blue by periodate at pH 9.0. T he reaction was monitored spectrophotometrically by measuring the decreasin g color of Nile Blue at 630 nm by the fixed time method. At a given time of 4.0 min at 30 degrees C, the working calibration range was 10-850 ng/mL Rh (III) and a detection limit of 8 ng/mL was obtained. No serious interferenc e was identified. The rhodium ion in synthetic and real samples was determi ned by this method with satisfactory results.