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Abstract Matrix effects are a recent remarkable feature in quantitative LC-MS/MS analysis. In this work, the matrix effects of a multiclass mixture of 46 analytes - pesticides, pharmaceuticals and perfluoroalkylsubstances in different types of natural groundwater were studied. Groundwater samples were spiked with different standards from different chemical groups and determined by direct injection and liquid chromatography coupled to tandem mass spectrometry. Matrix effects were assessed by matrix factors calculated using the slope ratio technique. Groundwater samples were sampled in different boreholes in several places in Slovakia. The relationship with the various detected inorganic parameters was investigated and discussed. Most of the studied analytes showed negative matrix effects. Some analytes showed weak negative or positive matrix effects. The results show that average matrix factors obtained from different sampling sites are not a reliable tool and matrix effects need to be monitored depending on the sampling location. Only weak or no correlation of the matrix factors with the determined inorganic parameters was found. Geochemical composition of boreholes samples was determined and the differences in the macrochemical composition of the samples was evaluated. Model samples of ultrapure water enriched with NaCl, Na 2 CO 3 and NaNO 3 at various concentration levels were tested and the matrix effects were not observed. Other content of sample than cations Na + were responsible for the matrix effects. It was found that the most affected compounds are sulfamethoxazole, sulfadiazine, metamitron, chloridazon and also caffeine. The results show that the detailed study is suitable as a tool for a deeper understanding of matrix effects in different types of groundwater. The proper ground water sample must be selected for reliable results of quantitative analysis. Graphical Abstract
Keršňáková et al. (Sat,) studied this question.