Continuous flow hydride generation laser induced fluorescence spectrometry for trace determination of lead in water and sediment samples

Abstract

Continuous flow hydride generation coupled with laser induced fluorescence spectrometry (HG-LIF) has been used for the determination of Pb in aqueous samples. Lead hydride is generated in K3Fe(CN)6-HCl medium using NaBH4 as the reducing agent. Parameters such as acidity and the concentrations of oxidising and reducing agents have been studied in order to obtain the highest sensitivity. Laser excitation of Pb has been performed at 283.306 nm and fluorescence has been detected at 365 nm and 405.8 nm. The limit of detection calculated for the optimised conditions (1% K3Fe(CN)6 in 0.3% Oxalic Acid, 0.055 mol L−1 HCl, 1% NaBH4 in 0.1% NaOH) is 0.3 ng mL−1. However, a significant Pb background was observed for blank measurements, which degraded the limit of detection. The limit of detection that is estimated for a Pb free blank was determined by detuning the laser to a wavelength of 282.806 nm and was found to be 0.45 pg mL−1. Method repeatability is 3.5% RSD at the 10 ng mL−1 level. The accuracy of this method has been evaluated by analysis of a water reference material. The results obtained for a multielement standard determined using the HG-LIF approach have been found to be in agreement with those obtained by using a comparison ICP-AES approach. The HG-LIF approach has been applied to the measurement of Pb in a contaminated sediment sample material. The results of this study demonstrate that a small tunable laser system combined with hydride generation sample introduction can be used to measure Pb with high sensitivity, precision and selectivity in different sample matrices.