Introduction Electrospray Ionization is one of the most utilized ionization techniques for LC-MS-based metabolomics [1]. However, it presents several drawbacks, e.g. the ion suppression phenomenon, causing ion intensity decrease [2]. The occurrence of the phenomenon is higher if the sample is more complex. Thus, studying samples with different complexities may lead to consider some non-significant molecular features as markers of discrimination. This is due to ion suppression in samples with higher complexity. Material and Methods The issue is reported in an environmental context [3,4]. The study is performed on control non-spiked sediment samples and sediments spiked with a complex biopesticide; Bacillus thuringiensis israelensis. Meta-metabolome (endometabolome + xenometabolome) is extracted with QuEChERS method, then analyzed by LC-QToF in order to perform untargeted metabolic profiling, to discover the biomarkers of exposure. This to understand the pesticide impact on spiked sediments compared to control sediments. Results and Discussion Results revealed several markers with lower intensity in the spiked group. They were co-eluting with multi-charged xenometabolites. Hence, these markers are either less concentrated due to a biological impact, or suppressed by the co-eluted molecules. Thus, to discriminate between biomarkers and suppressed ions, samples are diluted and analyzed. In fact, as dilution decreases the ion suppression, suppressed features are no more significantly discriminant between the two groups of samples. References [1] Bedair et al. 2008. Trends Anal. Chem. 27(3):238–250 [2] Antignac et al. 2005. Anal. Chim. Acta. 529(1–2):129–136 [3] Patil et al. 2016. Sci. Total Environ. 566–567:552–558 [4] Salvia et al. 2018. Environ. Sci. Pollut. Res. 25(30):29841–29847