Optimal acid digestion for multi-element analysis of different waste matrices

Informed planning and assessment of waste management systems requires accurate data on physical and chemical characteristics of the waste materials. For many parameters analytical standard methods already exist; however, most of these methods do not account for the specific properties of the distinct waste materials and recyclables. The purpose of this study is to evaluate the performance of different standardized microwave assisted acid digestion methods on waste samples and subsequent multi-element analysis. Six acid digestion methods were applied on a Paper & Cardboard and Composite waste matrix preparing four replicates per method. The digestates were subsequently analyzed for 20 elements using ICP-MS and ICP-OES. The measurement results were statistically evaluated using ANOVA and a ranking procedure. The ANOVA shows a significant difference between the digestion methods for 12 elements in the Paper & Cardboard matrix and for 10 elements in the Composite matrix. The ranking procedure points to different methods to be the most optimal digestion methods in the tested waste matrices. The recovery rates can vary by more than 90% among the tested digestion methods depending on the individual element. The selection of an appropriate method is therefore crucial.