Green direct ultrasonic slurry sampling and electrothermal atomic absorption spectrometry method for metal analysis of solid plastics samples

Abstract

This work presents a “green” analytical method developed for the determination of potentially toxic metals such as aluminium, barium and chromium in solid plastics samples using the slurry sampling technique in conjunction with electrothermal atomic absorption spectrometry. The development of the slurry sampling technique in conjunction with electrothermal atomic absorption spectrometry entailed optimisation of the measuring conditions, which included optimisation of the temperature programme, selection of an appropriate liquid medium for slurry preparation, optimisation of the concentration and volume of the liquid medium and optimisation of the mass of the solid plastics sample. The following conditions were determined: the optimal pyrolysis temperature for aluminium, barium and chromium was in the range of 1300 °C to 1700 °C and the optimal atomisation temperature was in the range of 2100 °C to 2400 °C. The optimal liquid media for solid plastics samples were H₂O, 0.2% (v/v) HNO₃ and 0.2% (v/v) HCl. The optimal volume of liquid medium was in the range from 5 to 15 mL and the mass of the solid plastics samples was in the range from 30 to 100 mg. The limit of detection and limit of quantification were estimated as 0.06–0.52 ng g⁻¹ and 0.22–1.69 ng g⁻¹ for aluminium, 0.11–0.94 ng g⁻¹ and 0.37–3.14 ng g⁻¹ for barium and 0.07–0.31 ng g⁻¹ and 0.25–1.04 ng g⁻¹ for chromium. Relative standard deviation was below 5% for all plastic samples analysed. Based on the established validation parameters, the slurry sampling technique in conjunction with electrothermal atomic absorption spectrometry represents a viable technique for metal analysis of a variety of plastic materials. The concentrations of analytes in individual solid plastic samples were in the range of 1.36 ± 0.06 μg g⁻¹ to 22.65 ± 0.66 μg g⁻¹ for aluminium, 1.13 ± 0.03 μg g⁻¹ to 6.01 ± 0.22 μg g⁻¹ for barium and 0.60 ± 0.03 μg g⁻¹ to 10.48 ± 0.46 μg g⁻¹ for chromium.