Optimization of flame atomic absorption spectrometry with preconcentrationby flow-injection on-line sorbent extraction of cadmium and lead in biological materials

A flow-injection (FI) system with a minicolumn of bonded silica with octade cyl groups (C-18) to collect diethyldithiocarbamate complexes of Cd and Pb in reference solutions and in acid-digested hair and blood solutions was de veloped and evaluated by flame atomic absorption spectrometry (FAAS). The s ystem was optimized by multivariate method, based on a factorial experiment al design in two levels, selecting eight parameters that mostly affected th e expected analytical signal. The detection limits (3(x)S(BL)/ slope, 60 s preconcentration) were 0.7 and 5 mu g/l for Cd and Pb, respectively and the sampling frequency was 40 samples/h. Effects of interfering ions are discu ssed. The methodology was validated by analysis of certified reference mate rials of hair and blood for Pb, and by recoveries of Cd and Pb spikes perfo rmed in hair and blood samples. Results for Pb agreed well with certified v alues and recoveries were satisfactory (103% in blood and 100% in hair). Al so, the recovery of Cd in hair was fair (107%); however, in blood it was no t quantitative (22%).