FLOW-INJECTION ONLINE COPRECIPITATION PRECONCENTRATION FOR ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY

A flow injection on-line coprecipitation system has been synchronously coupled to an electrothermal atomic absorption spectrometric system for the determination of trace amounts of heavy metals in whole blood digests. Cadmium and nickel in the digest were coprecipitated with the iron(II)-hexamethylenedithiocarbamate (HMDTC) complex on the walls of a knotted reactor without using a filter. The precipitate was dissolved in 60-mu-l of isobutyl methyl ketone and stored in a poly(tetrafluoroethylene) tube before introduction onto the platform of a graphite furnace carried by a stream of HMDTC reagent. Electrothermal atomic absorption spectrometric determination of the analyte was performed in parallel with the preconcentration of the next sample. Enrichment factors of 16 and 8 were obtained for cadmium and nickel, respectively, using 20 and 40 s precipitate collection times, at a sample flow-rate of 3 ml min-1 for cadmium and 2 ml min-1 for nickel. The detection limits (3-sigma) were 0.003 and 0.02-mu-g l-1 for cadmium and nickel, respectively, and the precisions were 5.9% relative standard deviation (RSD) at the 0.02-mu-g l-1 level for cadmium, and 6.0% RSD at the 1.5-mu-g l-1 level for nickel. Recoveries of cadmium and nickel in blood digests were 103 and 106%, respectively.