On-line flow injection solvent extraction for electrothermal atomic absorption spectrometry: Determination of nickel in biological samples

Abstract

A flow injection (FI) on-line solvent extraction system for electrothermal atomic absorption spectrometry (ETAAS) was developed with nickel as a model trace element. The nickel pyrrolidine-dithiocarbamate chelate was extracted on line into isobutyl methyl ketone, which was delivered into the FI system by a peristaltic pump equipped with poly(tetrafluoroethylene) tubing. The organic phase was separated from the aqueous phase by a novel gravity phase separator with a small conical cavity, and stored in a collector tube, from which 50 μl organic concentrate was introduced into the graphite tube by an air flow. ETAAS determination of the analyte was performed in parallel with the extraction process. An enrichment factor of 25 was obtained in comparison with 50 μl direct introduction while achieving a detection limit of 4 ng l −1 (3σ), and a precision of 1.5% relative standard deviation for 1.0 μg l −1 nickel ( n = 11). The proposed method was successfully applied to the determination of nickel in body fluids and other biological samples.