Highly Sensitive Determination of Trace Molybdenum (VI) by Catalytic Kinetic Spectrophotometry

A sensitive, simple, new catalytic-kinetic spectrophotometry method is proposed for determination of trace molybdenum (VI) which is based on the molybdenum's significant catalysis to the fading reaction between carboxyazo I and KIO₄ which is quasi-zero-order reaction. The optimum reaction conditions were: 1.0 mL carboxyazo I, 1 mL KIO₄, 2.0 mL acetate buffer of pH 5.0plusmn0.05 and at 100degC. Following the recommended procedure, the linear range of this assay was from 0.15 to 10.5 ngldrmL^-1 (r=0.9967). The limit of detection was 0.03 ngldrmL^-1. The relative standard deviation for the determination of 5.0 ngldrmL^-1 molybdenum (VI) was below 2.1% (n=6). The proposed method was applied to the determination of molybdenum (VI) in environment water with satisfactory results.