Quantification of heavy metals for the recycling of waste plastics from electrotechnical applications

Analytical data on element concentrations in plastics is an important prerequisite for the recycling of technical waste plastics. The chemical resistance and high additive contents of such materials place a high demand on analytical methods for quantifying elements in thermoplastics from electrotechnical applications. The applicability of three common independent analytical methods (EDXRF, AAS, ICP-AES) for the quantification of heavy metals in such technical waste plastics of varying composition was studied. Following specific sample pre-treatments, such as closed vessel microwave assisted digestion and wet ashing with H2SO4, three hazardous metals (Pb, Cd, Sb) were determined. Conditions were investigated to minimize matrix effects for all analytical techniques employed. The trueness for the quantification of Cd was checked by using the certified reference material VDA 001–004 (40–400 μg g−1 Cd in polyethylene), and no significant differences to certified values were found. The best detection limits were found to be 2, 1.3 and 7.9 μg g−1 for Cd, Pb and Sb, respectively. In technical waste polymers, Sb was detected to be in the range 1–7%, Cd in the range 80–12 000 μg g−1 and Pb in the range 90–700 μg g−1. The precision reached for the analysis of this complex material, is comparable for all methods, and can be expressed by a relative standard deviation smaller than 8%. Application of multivariate analysis of variances (MANOVA) showed no differences between the mean results, except for the ICP-AES analysis following wet ashing with H2SO4.