TZW’s name „German Water Centre“ does not reflect fully its program anymore when it comes to the analysis of organic micropollutants. Since years, TZW’ experts deal with the analysis of considerably more complex environmental samples than just water. While analysis of drinking water most often does not entail major difficulties, analysis of wastewater, soil, sludge or of vegetable and animal biota samples exhibits a variety of challenges with regard to sample preparation and measurement.
Impurities compromise the analytical performance
Industrial wastewaters, sewage sludge, soil, complete plants or parts of samples as lettuce leafs, wheat grains, wheat flour, topinambur tubers or soybean flour, herring gull eggs, earthworms or fish liver are only few examples for samples, which have been analysed at TZW’s lab in the past few months. Quite often analysis targeted at per-and polyfluorinated alkyl substance (PFAS), but pharmaceutical residues or specific industrial chemicals were also covered. For all these sample matrices, sample constituents might cause major problems during target analysis of trace pollutants. The effects caused by these interfering constituents have either to be eliminated or at least reduced or to be compensated in order to enable a sensitive and reliable analysis.
Adapted strategies
In some cases, interferences by matrix constituents can be significantly reduced by diluting the samples or sample extracts. Quite often, however, this step is insufficient and tailor-made pre-treatment steps are needed. Modification and optimisation of the chromatographic separation might also be an appropriate tool for removal of the majority of interfering substances without discriminating the target compounds. Matrix effects can be compensated by using internal standards with similar chemical structure (e.g. isotope-labelled compounds). Last but not least, standard addition as a labour-intensive method can be used to overcome problems caused by the matrix.
Examples
Evaluation of time series for different plant samples (leafs from beech or poplar trees) illustrated the increasing atmospheric deposition of trifluoroacetic acid (TFA) into the terrestrial environment.
Analysis of plant samples from field trials and from greenhouse experiments yielded relevant information about the transfer from PFAS from soil to plants and about differences in contamination patterns between different plant species and between different plant parts.
Analysis of fish which were caught in a river downstream a wastewater treatment plant discharge proved the instantaneous effect of implementing an additional treatment step on contamination of fish organs by pharmaceutical residues. Finally, analysis of wild boar liver from animals from different locations yielded a relatively high contamination with PFAS in the Mittelbaden region.
