Determination of (ultra) trace amounts of lead in biological materials by on-line coupling flow injection microcolumn separation and preconcentrationto electrothermal atomic absorption spectrometry using a macrocycle immobilized silica gel sorbent

A fully automated procedure was developed for the determination of (ultra)t race lead in biological materials by on-line coupling flow injection (FI) m icrocolumn separation and preconcentration with electrothermal atomic absor ption spectrometry (ETAAS) using a macrocycle immobilized silica gel sorben t (Pb-02). The analyte was selectively and efficiently collected on a conic ally shaped column (50 mu l) packed with Pb-02 over a wide range of sample acidity (0.08-greater than or equal to 3 mol l(-1) HNO3). Quantitative elut ion of the retained analyte from the column was achieved with 46 mu l of 0. 03 mol l(-1) ethylenediamine tetraacetic acid (EDTA) solution at pH 10.5. T he eluate was driven with an air flow into the graphite tube preheated to 1 10 degrees C. No precise timing was needed during analyte elution and eluat e introduction. When 0.15 mol l(-1) HNO3 was used as the wash medium and th e residual solution was removed from the column and connecting tubes by air before elution, the only potential interferents were found to be Ba(ii), S r(ii) and K(i) due to their competition for the cavity of the macrocyclic c ompound because their ionic radii are similar to that of Pb(ii). Neverthele ss, these potential interferences were eliminated or minimized by a proper increase of eluent volume and/or EDTA concentration. Under the optimized co nditions, the tolerated concentrations of Ba(ii), Sr(ii) and K(i) were at l east 10, 100 and 5000 mg l(-1) in the digest, respectively. With a sample l oading rate of 3 ml min(-1) and a 20-s preconcentration time, an enhancemen t factor of 23 and a sampling frequency of 23 h(-1) with a collection effic iency of 70% were obtained. The detection limit (3s) was found to be 2 ng l (-1). The relative standard deviation (n=9) was 2.9% at the 500 ng l(-1) Pb level. The results for a number of standard reference materials (rice flou r, blood and urine) demonstrated the applicability of the proposed method t o the analysis of biological materials with simple aqueous standards for ca libration.