A flow injection online micelle-mediated preconcentration and separation procedure without phase separation coupled with electrothermal atomic absorption spectrometry for determination of trace lead in biological samples

A new flow injection online micelle-mediated preconcentration and separation procedure other than cloud point extraction was developed for electrothermal atomic absorption spectrometric (ETAAS) determination of trace lead in biological samples. The procedure involved the formation of the analyte-entrapped surfactant micelles by online merging of the analyte solution with an ammonium pyrrolidine dithiocarbamate (APDC) solution and a Triton X-114 solution sequentially, the adsorption of the resultant analyte-entrapped surfactant micelles onto a microcolumn packed with silica gel, and online elution of the adsorbed analyte with 50 mul of acetonitrile for ETAAS detection. The operations for the phase separation of the analyte-entrapped surfactant micelles from aqueous solution (such as heating, addition of salting-out agents, filtration or centrifugation) which was always required in conventional cloud point extraction was avoided in the developed methodology, facilitating the online combination of the micelle-mediated preconcentration with a flow injection system. With consumption of 2.2 ml sample solution, a detection limit of 44.6 ng l(-1), and a concentration factor of 22.5 were obtained at a sample throughput of 30 samples h(-1). The precision (RSD) for 11 replicate measurements of 1 mug l(-1) Pb was 2.9%. The developed methodology was successfully applied to the determination of trace lead in several certified biological reference materials.