DETERMINATION OF TRACE AMOUNTS OF MOLYBDENUM IN RAINWATER AND SNOW BYGRAPHITE-FURNACE ATOMIC-ABSORPTION SPECTROMETRY AFTER SOLVENT-EXTRACTION AND MICROVOLUME BACK-EXTRACTION

A method for the determination of trace amounts of molybdenum at ng l( -1) levels in rainwater and snow is described. Molybdenum is extracted into xylene as a complex of N-benzoyl-N-phenylhydroxylamine (BPA), an d subsequently back-extracted into 100 mu l of nitric acid for a deter mination by graphite-furnace atomic absorption spectrometry (GFAAS). T he extraction and micro-volume back-extraction allows molybdenum to be concentrated about 6000-fold. The back-extracted solution is suitable for the determination of molybdenum by GFAAS. The conditions of extra ction and back-extraction, such as acidity, concentration of BPA, and amount of nitric acid, were investigated. The detection limit for moly bdenum is 0.54 ng l(-1) based on a 1700-fold preconcentration. The app lication of this method to the determination of molybdenum in various samples of rain-water and snow is demonstrated.