Novel Reaction for Rapid, Simple, and Sensitive Determination of Molybdenum in Various Samples

Abstract

A new sensitive, selective, rapid, and reproducible method is presented for the analysis of trace amounts of molybdenum (VI) (Mo(VI)). The method is based on the reaction of molybdenum (VI) with a new analytical reagent, 6‐(5‐Chloro‐2‐hydroxy‐4‐sulfophenylazo)‐5‐hydroxy‐1‐naphthalenesulfonic acid, disodium salt. Under optimum reaction conditions, molybdenum (VI) forms a red complex with a maximum absorption peak at 589 nm. The color reaction is rapidly completed at room temperature. The apparent molar absorption coefficient and Sandell sensitivity were 1.13×10⁴ L · mol⁻¹ · cm⁻¹ and 0.0084 µg · cm⁻², respectively. Beer's law was obeyed up to 8.5 µg · mL⁻¹. Methods for the determination of Mo(VI) by first‐derivative spectrophtometry have also been proposed at 547 and 625 nm. The proposed methods offer the advantages of sensitivity, rapidity, selectivity, and simplicity without any prior separation or extraction. The methods have been applied to the determination of Mo(VI) in various environmental samples and some alloys; satisfactory results have been obtained.

Keywords:

• Spectrophotometry
• derivative spectrophotometry
• Mo(VI)
• 6‐(5‐Chloro‐2‐hydroxy‐4‐sulfophenylazo)‐5‐hydroxy‐1‐naphthalenesulfonic acid
• disodium salt