ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRIC DETERMINATION OF CADMIUM AND LEAD IN BLOOD USING FLOW-INJECTION ONLINE SORPTION PRECONCENTRATION IN A KNOTTED REACTOR

A flow injection on-line sorption separation system combining a knotte d reactor (KR) and two sorbent extraction columns was developed for th e electrothermal atomic absorption spectrometric determination of (ult ra) trace amounts of cadmium and lead in freeze-dried blood samples. T he diethyldithiophosphate complexes of the analytes were selectively a dsorbed on the inner walls of the PTFE KR. The chelating reagent was o n-line purified using conical sorbent extraction columns packed with 2 0 mg of C-18 bonded silica gel. The collected analyte complexes were q uantitatively eluted from the 100 cm KR with 35 pi of methanol and the eluate was directly introduced into a pyrolytically coated graphite t ube pre-treated with iridium modifier. Enhancement factors of 26 and 9 9 and detection limits of 0.2 and 1.6 ng l(-1) were obtained for cadmi um and lead, respectively. The relative standard deviation was 2.1% fo r 0.02 mu g l(-1) cadmium and 2.7% for 0.2 mu g l(-1) lead. The spike recovery was between 90 and 100%. The results from the analysis of bio logical reference materials agreed with the certified or indicated val ues. (C) 1998 Elsevier Science B.V. All rights reserved.