A Rapid Spectrophotometric Method for Micro-determination of Molybdenum in Alloy Steels and Environmental Samples

A highly selective extractive spectrophotometric method for micro-determination of molybdenum has been presented. Employing ascorbic acid as a reductant, Mo(VI) was reduced to Mo(V) at the room temperature in 1 mol L –1 H 2 SO 4 . The obtained Mo(V) formed a yellow-colored (1:2) complex with 3-hydroxy-2-(4-methoxyphenyl)-6-propionyl-4-oxo-4H-1-benzopyran (HMPB). The complex was quantitatively extracted to 1,2-dichloroethane and absorbance of the extract was measured at 414 nm. The Beer’s law was obeyed up to concentration 2.45 µg mL –1 with molar absorptivity and Sandell's sensitivity of 5.43 × 10 4 L mol –1 cm –1 and 0.0017 µg cm –2 , respectively. The relative standard deviation and coefficient of variance were ± 0.0025 (in absorbance units) and ± 0.25% for 10 replicate determinations of 1 µg mL –1 analyte. The method was free from the interference from a large number of analytically important elements and has been applied satisfactorily to the determination of molybdenum in various synthetic, environmental, and technical samples with the improved accuracy and precision.