Determination of Lead in Seawater by Flow-Injection On-line Preconcentration-Electrothermal Atomic Absorption Spectrometry after Coprecipitation with Iron(III) Hydroxide

摘要

A flow-injection on-line preconcentration-electrothermal atomic absorption spectrometric (ETAAS) method coupled with a coprecipitation method has been developed for the determination of lead in seawater. The combination of two preconcentration procedures, coprecipitation with iron(III) hydroxide and solid-phase extraction with a lead-selective resin, Pb·SpecTM, allowed the determination of lead at the ng kg-1 level. Lead in 250 g of a sample solution was collected by coprecipitation with 10 mg of iron. The precipitate was dissolved in 25 ml of 1 mol l-1 nitric acid; then, a 4-ml aliquot of the sample solution was introduced into the flow-injection system to preconcentrate and separate lead from iron on a Pb·Spec microcolumn. The sorbed lead was eluted with a 1.0 × 10-4 mol l-1 EDTA solution. The 30-μl portion of the eluate corresponding to the highest analyte concentration zone was injected into a graphite furnace. The overall enhancement factor was about 200 for 250 g of the sample. The average and standard deviation of ten blank values obtained were 1.7 ng and 0.38 ng, respectively. The recovery was 93.7 ± 5.0% for seawater spiked with 20 ng kg-1 lead. The proposed method is applicable to the analysis of seawater for lead at slightly higher levels.