Investigations on sample pretreatment for the determination of selected metals and organochlorine compounds in suspended particulate matter of the River Elbe

The River Elbe and some of its tributaries are transporting polluted suspended particulate matter (SPM). Due to the property of SPM to accumulate anthropogenic and nonanthropogenic substances, this matrix is of interest from an analytical point of view. SPM has been collected in 13 sampling devices, placed in monitoring stations along the River Elbe from the Czech border to the North Sea and the embouchures of its tributaries Schwarze Elster, Mulde and Saale. Characterization of the SPM has been carried out by sieving and determining the content of total carbon. Comparative studies with different digestion procedures are presented for the determination of heavy metals and arsenic in the fine grain particle size <20 m of freeze-dried SPM. In a first test the highest concentrations have been found for microwave heating in a closed system when using an acid mixture of HNO₃/HF 3:1. Results of an interlaboratory test show the good practicability of the microwave heating digestion method. The determination of organochlorine compounds in a freeze-dried sample by three different extraction methods including supercritical fluid extraction (SFE) with CO₂ shows that the highest extraction efficiency is found for the conventional Soxhlet method.