Application of 1,2-Dihydroxybenzene-3,5-disulfonic Acid for the Separation and Preconcentration of Trace Molybdenum and Its Determination by Third Derivative Spectrophotometry

Abstract

Molybdenum was quantitatively extracted form large volumes of aqueous solutions of various samples by 1,2-dihydroxybenzene-3,5-disulfonic acid (Tiron) and tetradecyldimethylbenzylammonium chloride (TDBA) on microcrystalline naphthalene in the pH range 6.5–8.5. After filtration, the solid residue consisting of molybdenum complex and naphthalene was dissolved in 5 mL of chloroform and molybdenum was determined by third derivative spectrophotometry. Alternatively, molybdenum can be quantitatively adsorbed on Tiron-TDBA-naphthalene adsorbent packed in a column and determined in a similar manner. About 0.02 µg of molybdenum can be concentrated in a column from 500 mL of aqueous sample, where its concentration is as low as 0.04 ng/mL. Various parameters such as the effect of pH, the volume of the aqueous phase, and the interference of a number of metal ions with the determination of molybdenum have been studied in detail to optimize the analysis of standard alloys and biological samples.