An automated on-line flow system for the pre-concentration and determination of lead by flame atomic absorption spectrometry

The use of Amberlite XAD-2 modified by 2-(2-benzothiazolplazo)-2-p-cresol (BTAC) as a sorbent in an on-line pre-concentration system for lead determination has been proposed. The procedure is based on the sorption of lead(II) ions onto a minicolumn packed with modified Amberlite XAD-2, followed by elution with 0.10 mol l(-1) hydrochloric acid and determination by flame atomic absorption spectrometry. The on-line flow system uses four three-way solenoid valves and is electronically controlled in a time-based mode. Chemical and flow variables were optimized. The results demonstrated that sample solutions containing lead(II) in the concentration range from 3.7 to 300.0 mug l(-1) in a solution of pH between 6.5 and 8.5 could be, determined, using a pre-concentration time of 2 min. The enrichment factor was 27 for a sample volume of 4.50 ml. The limit of detection was 3.7 mug l(-1). The relative standard deviations (R.S.D.) were in the range of 4.4-2.3% for lead concentrations from 50.0 to 300.0 mug l(-1), respectively. The method was tolerant to other ions usually present in biological samples. Good accuracy was assured by the analysis of biological reference materials. (C) 2001 Elsevier Science B.V. All rights reserved.