Abstract
Sample preparation is a very essential and crucial process in the analysis of trace elements in environmental samples using spectrometric techniques. This is because trace elements in the environmental matrices are present in very lower concentrations. In addition, the determination using spectrometric techniques can be a little difficult and their direct analysis is not possible. Spectrometric techniques need sample dissolution as they can only be analysed from the aqueous form, thus sample preparation being it digestion, extraction or preconcentration is needed. The aim of this study was to develop sample preparation techniques for preconcentration/extraction of trace metals in water and sediments samples prior to spectrometric determination. Three different sample preparation methods were investigated in this study. Sediments and water samples were prepared using conventional hotplate digestion, microwave digestion as well as preconcentration (ultrasound assisted dispersive solid phase microextraction) prior to inductively coupled plasma optical emission spectrometric (ICP-OES) analysis. The subsequent paragraphs give overview of each objective. Firstly, the determination of trace metals such as As, Cd, Cr, Cu, Pb, Fe and Zn by inductively coupled plasma optical emission spectrometry was performed in freshwater sediments collected from Mzimvubu river in Port St. Johns (Eastern Cape South Africa). The effectiveness of acid digestion in freshwater sediment samples using dilute nitric acid in a hotplate was evaluated. The optimization of the most influential factors was achieved using one factor at time (OFAT of univariate) approach and the optimal conditions for 1.00 g of sample, were 180 ℃, 45 min and 5.0 mol L−1 for temperature, digestion time and nitric acid concentration, respectively. The accuracy of the optimized method was evaluated by analysis of certified reference materials (CRM015-freshwater sediment and CRM052-loamy clay soil). The obtained results exhibited good agreement with the reference values of the CRM samples. The analytical method was applied to the determination of As, Cd, Cr, Cu, Pb, Fe and Zn in sediment samples. The proposed method displayed attractive features such as simplicity, environmentally friendly and safety compared to classical acid digestion procedures that use concentrated acids...
M.Sc. (Applied Chemistry)