Kinetic spectrophotometric determination of trace osmium by its catalytic effect on the oxidation of methlyene blue

A method is presented for the determination of Os(IV), based on the catalytic effect of Os(IV) on the oxidized reaction of methlyene blue(MB) by periodate. The reaction was monitored spectrophotometrically by measuring the discolor of methylene blue at 660 nm by the fixed time method, at a given time (14 min) and 90 degrees C. A linear relationship exists in the concentration range of 0 similar to 3.2 mu g/L for Os, and the detection limit is 2.03 x 10(-5) mg/L. The relative standard deviation for 1.6 mu g/L osmium is 1.6% (n = 11). The catalytic reaction is first-order in Os, MB, KIO4 and H-2 SO4, respectively. The apparent activation energy of catalytic reaction is 87.72 kJ/mol. The reaction mechanium is discussed. The proposed method has been applied to the determination of osmium in some ores and metallurgical products after a separation of osmium by distillation. The results obtained proved to be satisfactory.