Determination of trace amounts of molybdenum in natural waters by solvent extraction-atomic-absorption spectrometry, after chelating ion-exchange pre-concentration

Abstract

A method for the determination of molybdenum in natural waters in the micrograms per millilitre range is proposed. The method involves the preconcentration of molybdenum on a Chelex-100 chelating resin and subsequent elution with ammonia solution, followed by extraction with a complexing reagent, 1,4-dihydroxyphthalimide dithiosemicarbazone dissolved in NN-dimethylformamide - isoamyl alcohol (1 + 4), and a final direct determination by atomic-absorption spectrometry. The addition of ascorbic acid prior to extraction eliminates the interfering effect of several ions at the concentration levels normally found in natural waters. The sensitivity of the method is 0.3 µg 1^–1 for 1% absorption. The method has been applied to the determination of molybdenum in sea and surface waters.