Spectrophotometric determination of molybdenum using surfactant-mediated liquid–liquid extraction

A new spectrophotometric method has been developed for determination of molybdenum using surfactant- mediated liquid–liquid extraction. Molybdenum(V) obtained by ascorbic acid reduction in 2.5 M H2SO4 reacted spontaneously with thiocyanate and cetyl trimethyl ammonium bromide (CTAB), forming an intense orange yellow complex that was extracted quantitatively into 1,2-dichloroethane and absorbed at 460 nm. The absorbance of the extract was found to be stable for more than 24 h. Beer’s law was obeyed over the concentration range 0.1–4.2 µg Mo mL ^−1 of the extract. The linear range for an accurate determination was found to be 1.2–2.6 µg Mo mL ^−1 . The molar absorptivity and LOD of the procedure were 4.01 × 10^4 L mol ^−1 cm ^−1 and 0.00239 µg Mo mL ^−1 , respectively. The stoichiometry of the orange yellow complex (Mo:SCN:CTAB) was found to be 1:3:2. The effect of a large number of cations, anions, and complexing agents was studied. For 10 replicate determinations of 1 µg Mo mL ^−1 , the standard deviation was 0.014 concentration units with a relative mean error of ± 0.38%. The method developed was applied for determination of molybdenum in various alloy steels and a wide variety of biological and environmental samples, including different types of water samples.