Critical study using experimental design of the determination of lead by high-resolution continuum source hydride generation atomic absorption spectrometry

Abstract

The present study critically evaluates quartz tube (QT) atomisation and high-resolution continuum source hydride generation atomic absorption spectrometry (HR-CS HG-AAS) for the determination of lead. A full two-level factorial design was performed to characterise the effects of the following reagent concentrations on the analytical procedure: sodium tetrahydroborate, potassium hexacyanoferrate(III) and nitric acid. This chemometric tool demonstrated that an increasing acid concentration increases hydrogen production, which dilutes the analyte in the quartz tube during analytical measurements. The experimental conditions established in the final procedure were determined using a Box–Behnken design. The method was used to determine the concentration of lead in water samples, with limits of detection and quantification of 0.13 and 0.40 μg L⁻¹, respectively. Method precision, expressed as relative standard deviation (RSD), was 6.36% and was obtained with a 10.00 μg L⁻¹lead solution. The accuracy was confirmed by determining the lead concentration in the NIST standard reference material, SRM 1643d, for trace elements in natural water. This method was then used to determine the lead concentration in eighteen water samples collected in the São Paulo River (Bahia State, Brazil). The lead concentrations varied from 0.62 to 3.73 μg L⁻¹. All samples were also analysed by inductively coupled plasma mass spectrometry (ICP-MS). Statistical tests demonstrated that there was no difference between the results obtained by both procedures.