The readily accessible bio-fluids urine and blood are the most commonly used matrices in established and automated sample preparation strategies . Independent of the route of exposure, ingested compounds are typically anticipated in blood because this bio-fluid is in steady-state contact with most human tissues. Therefore, it may be considered as the best-suited matrix to characterize the chemical exposome . In parallel, complementary urinary analyses can shed light on short-lived compounds or excreted metabolites. Colorimetric assays to determine creatinine in urine and albumin in blood are typically implemented to report xenobiotic levels in relation to the respective bio-fluid concentrations (see Supplementary Table ).