In this study, a two-step preconcentration procedure is proposed to be used in conjunction with ICP-AES for the determination of trace metals in seawater. The two-step preconcentration involves extraction of trace metals from seawater with dithiocarbamate (DTC) into chloroform followed by back-extraction with a Pd2+ solution. The extraction could concentrate the trace metals by forming a chelate with DTC with a high enrichment factor obtained with the large phase volume ratio. The

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... n agent Pd2+ is selected because the extraction constant of Pd(DTC)2 is the largest and much higher than most of the other metal dithiocarbamates. The enrichment factor could be further enhanced at the back-extraction step with a large phase volume ratio. Finally, the aqueous solution containing simply the enriched metals and some of the nonreacted Pd2+ was taken for ICP-AES.