Flow injection on-line displacement sorption preconcentration coupled with flame atomic absorption spectrometry for the determination of trace lead in biological samples

A flow injection (FI) on-line displacement sorption preconcentration coupled with flame atomic absorption spectrometry (FAAS) for selective preconcentration and separation of trace lead in biological samples was developed. The method involved on-line formation of the Zn-sodium diethylammonium diethyldi-thiocarbanate (DDTC) complex and its presorption onto the microcolumn packed with cigarette filter, retention of the analyte Pb (II) onto the cigarette filter through a displacement reaction between the Pb (11) and the pre-sorbed Zn-DDTC, elution of the retained analyte with ethanol, and on-line detection by FAAS. Interferences from coexisting ions with lower stability of their DDTC complexes relative to Zn-DDTC were eliminated because they could not displace the Zn(II) from the presorbed Zn-DDTC. With a 90-s displacement sorption at a flow rate of 5. 0 mL/min, an enhancement factor of 33 with a detection limit (3s) of 2. 0 mu g/L was obtained. The precision (RSD, n = 11) was 1. 2% at the level of 100 mu g/L. The developed method was successfully applied to selective determination of trace lead in biological materials.