Determination of ultra-trace concentrations of elements by means of on-line solid sorbent extraction graphite furnace atomic absorption spectrometry

Summary

Solid sorbent extraction using a micro column in an automated system was successfully coupled with a graphite furnace for atomic absorption spectrometry. Bonded silica with octadecyl functional groups (C-18 reversed phase material) was used in a 15 μl conically shaped micro column as a sorbent for the metal complexes formed on-line with sodium diethyldithiocarbamate. Column elution was performed with ethanol as the eluent into a PTFE capillary used for eluate storage and transfer into the graphite tube. With a sample loading time of 60 s and the direct introduction of the eluate portion containing the highest analyte concentration into the graphite tube, an enrichment factor of approx. 20 could be realised. Effective elimination of contamination by the closed system and on-line purification of the complexing agent together with highly selective separation of the trace metals from alkaline and earth alkaline elements allowed the determination of ultra-trace metals in seawater and deionised water. Using only 3 ml of sample detection limits for cadmium, cobalt, copper, lead, and nickel of 0.8, 12, 17, 6.5 and 36 ng/l, respectively, could be achieved.