ABSTRACT
A rapid simple, accurate and sensitive spectrophotometric method was developed for the determination of a low concentration of molybdenum in pure and in complicated matrix. It is based on the extraction of the ion-pairs of Mo [V]-thiocyanate-chloroquine [1] and Mo [V]-thiocyanate-pyrimethamine [2], which are orange-red in color into dichloromethane from hydrochloric acid medium. The ion-pairs have an absorption maximum at gamma = 467 and 471 nm with molar absorptivities [epsilon] of 6.16 x 103 and 5.80 x 103 1/mol/cm for the Mo [V] ion- pairs [1] and [2]. The Sandell sensitivity was found to be 0.027 and 0.042 mug/cm2 for [1] and [2]. The effect of temperature, reagent concentration, time and diverse ions upon the absorbance of the ion- pairs was critically assessed. Beer's law was valid over a concentration range of 2.0-22.0 and 2.0-25.0 mug Mo/ml in case of [1] and [2]. Both reagents [chloroquine and pyrimethamine] were successfully applied for the determination of molybdenum in synthetic mixtures and molybdenum steels