Alkaline solubilization and ultrasound assisted extraction for Cr and Pb determination in leather by atomic absorption spectrometry

Abstract

Alkaline solubilization with tetramethylammonium hydroxide (TMAH) and ultrasound-assisted extraction as sample preparation procedures were evaluated for the extraction and subsequent determination of Cr and Pb in leather samples by flame atomic absorption spectrometry (FAAS). In the alkaline solubilization with TMAH, 0.10 g of the sample was heated to 95 ± 5 °C for 30 minutes in the presence of 2.75 mol L⁻¹ TMAH in methanol medium. The procedure provided complete solubilization of the sample, resulting in limits of detection of 4 μg g⁻¹ for Cr and 9 μg g⁻¹ for Pb; the obtained RSD values were lower than 9.7%. Ultrasound-assisted extraction was evaluated with aliquots of 0.15 g of the sample, using HNO₃, aqua regia and HCl as extraction solutions. However, this procedure was effective only for Pb extraction, using HNO₃ and aqua regia as extractants. The limits obtained for Pb detection of 4 μg g⁻¹ and RSD values lower than 3.8% were adequate for the determination. The simplicity of the proposed procedures for sample preparation, the reduced amounts of reagents required, minimizing contamination risks, and the low cost of the required instrumentation make these procedures excellent alternatives for the preparation of leather samples for elementary analysis.