Central composite design for the optimisation of Cd and Pb determination in PVC materials by atomic absorption spectrometry after Kjeldahl digestion

A convenient and simple wet acid digestion method was developed for the determination of Cd and Pb concentrations in polyvinyl chloride matrices by atomic absorption spectrometry. Response surface methodology (RSM) was used to optimise the conditions for maximum recovery and to understand the significance and interaction of the factors affecting the recovery of Cd and Pb. The central composite design was employed to evaluate the effects of nitric acid volume (2.6-9.4 mL), sulphuric acid volume (0.6-7.4 mL) and certified reference material (CRM) amount (0.1-0.5 g) on the metal recoveries (60 min, 200 °C and 20 min, 250 °C). The accuracy was also evaluated using the polyvinyl chloride reference material Fluxana FLX-PVC2. The apparent recoveries of the elements relative to the certified values ranged from 0.94 (Cd) to 0.92 (Pb). The method's detection limits were found to be 1.6 and 6.4 mg kg−1 for Cd and Pb, respectively.