Flow Injection On-line Sorption Separation and Preconcentration With a Knotted Reactor for Electrothermal Atomic Absorption Spectrometric Determination of Lead in Biological and Environmental Samples

Abstract

A selective and robust flow injection on-line sorption separation and preconcentration 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 the other metals in digested biological and diethyldithiocarbaenvironmental samples. The collected analyte complex was eluted quantitatively with 35 μl of ethanol and all the eluate was directly introduced into the graphite tube without a L’vov platform by an air flow. Neither a pre-heating step nor precise timing was needed during elution and eluate introduction. ETAAS determination of the concentrated analyte was carried out in parallel with the next preconcentration cycle. An enhancement factor of 125 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 sample flow rate of 5.4 ml min−1. The precision for 11 replicate determinations at the 0.5 μg l−1 Pb level was 2.1% (RSD). The analytical results for a number of biological and environmental certified reference materials were in good agreement with the certified values.