Automated trace enrichment and determination of metals using a combination of supported liquid membrane for sample pretreatment and graphite furnace atomic absorption spectrometry for the determination

A computer controlled system has been developed for automated trace analysis for metals. The system used consists of four parallel supported liquid membrane devices for analyte enrichment, leaving an efficiently cleaned and enriched sample in the acceptor for the final analytical step, which is performed by graphite furnace atomic absorption spectrometry (AAS). The system was tested with 40% di(2-ethylhexyl)phosphate in kerosene as the liquid in the porous membrane and with the model metals Al, Cd and Cu at concentrations below mu g/l. The average relative standard deviation (RSD) was 6.5% at 0.5 mu g/l and 6.3% at 1.0 mu g/l based on 108 independent measurements. The blank for Al, which is the most difficult metal to determine with respect to contamination was 0.15 mu g/l with an average RSD (n=16) of 11%. Using a 30 min period for processing the samples in the supported liquid membrane step, the sample throughput was eight samples per hour.