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

摘要

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) H2SO4. The obtained Mo(V) formed a yellow-colored (1:2) complex with 3-hydroxy-2-(4-methoxyphenyl)-6-propiony 1-4-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 x 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.