A comparison between a targeted and an untargeted approach in the frame of a pilot biomonitoring study

Introduction Exposure to environmental toxicants can be assessed through the determination of metabolites of chemicals in biofluids. Targeted and untargeted approaches can be applied to characterize the “exposome”, both with advantages and disadvantages [1]. The aim of this work was to compare the results of a pilot biomonitoring study obtained both with a targeted quantification of urinary mercapturic acids, metabolites of volatile organic compounds, and with an untargeted approach. Technological and methodological innovation Urine samples were collected from 67 adults: 38 non-smokers, 7 electronic cigarette smokers, and 22 traditional smokers. 17 mercapturic acids were quantified with a validated isotope dilution LC-MS/MS method, using a triple-quadrupole mass spectrometer [2]. Using the same chromatographic conditions, the untargeted approach was performed with a time-of flight operating in data dependent mode; data were processed using XCMS and the ANOVA test was used to detect significant features among groups. Results and impact Most analytes were quantified in all samples with the targeted approach. 3613 features were identified in the untargeted assay, among which only five mercapturic acids were present; seven mercapturic acids were not identified as a feature but detected inspecting the chromatograms; and four mercapturic acids were not detected at all in the untargeted approach. Despite its promising ability to characterize exposome, the untargeted approach may not detect chemicals present at low levels. References [1] Dennis et al. 2017. Environ Health Perspect. 125, 502-510 [2] Frigerio et al. 2019. J Chromatogr B Analyt Technol Biomed Life Sci. 1117, 66-76.