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 an alysis for metals. The system used consists of four parallel supported liquid membrane devices for analyte enrichment, leaving an efficientl y cleaned and enriched sample in the acceptor for the final analytical step, which is performed by graphite furnace atomic absorption spectr ometry (AAS). The system was tested with 40% di(2-ethylhexyl)phosphate in kerosene as the liquid in the porous membrane and with the model m etals Al, Cd and Cu at concentrations below mu g/l. The average relati ve 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 wa s 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.