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

Abstract

The use of Amberlite XAD-2 modified by 2-(2-benzothiazolylazo)-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 μg 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 μg 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 μg 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.