Determination of lead by flow injection hydride generation atomic absorption spectrometry with tetrahydroborate immobilized on an anion-exchange resin

Abstract

The efficiencies of four types of strongly basic anion-exchange resins in the tetrahydroborate form for the generation of lead hydride, used in the determination of lead by quartz tube (QT) atomization AAS, were investigated. Amberlyst A-26 gave the highest peak-height and peak-area sensitivities. The effects of column dimensions, tetrahydroborate concentration, loading time, loading direction, carrier reagent flow rate, carrier gas flow rate, sample acidity, and stripping coil length were studied. Without the argon carrier gas, the sensitivity was improved almost five times, though the precision was dependent on carrier agent and waste flow rate. Three procedures for the purification of potassium hexacyanoferrate(III) were investigated; a batch procedure, based on plumbane generation, was found to be the most effective. The concentration of acid was critical. Interferences from coexisting cations and anions were investigated. Hydride forming elements and phosphate interfered, but less suppression than for conventional HG-AAS was observed for some species. The limit of detection (3s) in 3% K₃Fe(CN)₆ and 0.10 mol l⁻¹ HNO₃ was 0.25 μg l⁻¹, with a sampling frequency of 20–40 h⁻¹. The precision, expressed as RSD, was 6.4% and 3.5% (n = 5) at concentrations of 3.0 and 5.0 μg l⁻¹, respectively. The method was applied to the analysis of different types of biological matrices including natural waters, wine, human saliva and human urine. The detection limits (3s) were 0.20–0.85 μg l⁻¹ for natural waters and 3.1–5.2 μg l⁻¹ for the wine, human saliva and human urine. Recoveries for spiked samples were 86–110%. The results of the analyses of NIST standard reference materials, freeze-dried urine (SRM 2670), and apple leaves (SRM 1515) were in agreement with the certified values and the results for San Joaquin soil (SRM 2709) agreed with the leaching recovery values.