FLOW-INJECTION ONLINE SORPTION SEPARATION AND PRECONCENTRATION WITH AKNOTTED REACTOR FOR ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRIC DETERMINATION OF LEAD IN BIOLOGICAL AND ENVIRONMENTAL-SAMPLES

A selective and robust Bow injection on-line sorption separation and p reconcentration procedure was developed for the ETAAS determination of (ultra)trace amounts of lead in biological and environmental samples. With the use of diethyldithiophosphate as complexing agent and citric acid as masking agent, the analyte complex was selectively formed and adsorbed onto the inner, walls of a PTFE knotted reactor at pH 0.5-3. 5 with removal of the high-content salts in saline water and most of t he other metals in digested biological and environmental samples. The collected analyte complex was eluted quantitatively with 35 mu l of et hanol and all the eluate was directly introduced into the graphite tub e without a L'vov platform by an air Bow. Neither a pre-heating step n or precise timing was needed during elution and eluate introduction. E TAAS determination of the concentrated analyte was carried out in para llel with the next preconcentration cycle, An enhancement factor of 12 5 and a detection limit (3s) of 4.8 ng l(-1) Pb, along with a sampling frequency of 31 h(-1), were achieved with a 60 s loading time at a sa mple Bow rate of 5.4 mi min(-1). The precision for 11 replicate determ inations at the 0.5 mu g l(-1) Pb level was 2.1% (RSD), The analytical results for a number of biological and environmental certified refere nce materials were in good agreement with the certified values.