SIMULTANEOUS DETERMINATION OF TRACES OF IRON, COBALT, NICKEL, COPPER,MERCURY AND LEAD IN WATER BY ENERGY-DISPERSIVE X-RAY-FLUORESCENCE SPECTROMETRY AFTER PRECONCENTRATION AS THEIR PIPERAZINO-1,4-BIS(DITHIOCARBAMATE) COMPLEXES

A bidentate chelating agent has been proposed to preconcentrate seven metal ions dissolved in an aqueous sample for their simultaneous deter mination using energy-dispersive x-ray fluorescence spectrometry. The metal ions are precipitated as their polymeric piperazino-1,4-bis(dith iocarbamate) chelates, which are then collected by vacuum filtration o n a Millipore membrane filter for direct examination by x-ray fluoresc ence analysis. Iron, cobalt, nickel, copper and zinc are determined by means of their K(alpha) x-rays and mercury and lead by means of their L(alpha) x-rays. A detection limit in the mug l-1 range can be achiev ed for all metals tested in 250-ml water samples with a counting time of 600 s. Effective precipitation of all metals occurs at pH 6-7. The recoveries of eight analyses of the metals in a multielement standard using the proposed method ranged from 97 to 105% and the precision ran ged from 2.3 to 3.1%. High concentrations of calcium and magnesium do not interfere with the method. The method is simple, sensitive and acc urate, and has been used for the simultaneous determination of the sev en metals under study in environmental samples and synthetic mixtures.