Automated on-line solvent extraction and AAS-graphite furnace determination of trace metals in difficult matrices

Abstract

A simple automated on-line extraction system for AAS-graphite furnace determination of trace metals in difficult matrices has been developed. The system uses solvent extraction of aqueous trace metals as diethyldithiocarbamate complexes into methyl isobutyl ketone fed directly to a graphite furnace for AAS determination. It was shown that complete extraction of the metals Cd, Co, Cu, Ni, Pb and Zn was possible under acid conditions at pH below 2. Since such a low pH is often encountered in acid digests of various materials it is possible to extract the metals directly from these digests. The extraction system was tested for Cd, Cu and Pb for a number of reference materials (soil, sediment, plant, animal tissue and bone). The accuracy of the total analytical procedure including the automated extraction was satisfactory and the results agreed well with the certified values within the tabulated standard deviations. By using the developed system tedious and contaminating sample preparation is minimized, and interference from matrix constituents (salts and Fe) is absent. The system is relatively simple to construct utilising general laboratory components, and it has been in service for many years at our laboratories, substantially cutting down laborious manual work and resulting in an increased output and higher quality of the analytical results.