Electrothermal atomic absorption spectrometric determination of cadmium and lead in blood using flow injection on-line sorption preconcentration in a knotted reactor

A flow injection on-line sorption separation system combining a knotted reactor (KR) and two sorbent extraction columns was developed for the electrothermal atomic absorption spectrometric determination of (ultra) trace amounts of cadmium and lead in freeze-dried blood samples. The diethyldithiophosphate complexes of the analytes were selectively adsorbed on the inner walls of the PTFE KR. The chelating reagent was on-line purified using conical sorbent extraction columns packed with 20 mg of C-18 bonded silica gel. The collected analyte complexes were quantitatively eluted from the 100 cm KR with 35 pi of methanol and the eluate was directly introduced into a pyrolytically coated graphite tube pre-treated with iridium modifier. Enhancement factors of 26 and 99 and detection limits of 0.2 and 1.6 ng l(-1) were obtained for cadmium and lead, respectively. The relative standard deviation was 2.1% for 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 biological reference materials agreed with the certified or indicated values. (C) 1998 Elsevier Science B.V. All rights reserved.