In particular, instruments from an alternative vendor were used for the low-resolution measurements. The variation in instrumentation and investigated analytes may explain the observed higher discrepancy between QQQ and HRMS in our measurements. For several analytes, the quantitation of the targeted analytes was successful on both instruments and the obtained results were comparable. The high correlation (>0.98) and no significant difference between both data sets for the measured analyte concentrations within the linear calibration range of the respective compound confirmed the potential of HRMS to produce accurate quantitative results. The agreement between data acquired with QQQ and HRMS has previously been demonstrated in several studies covering, e.g., endogenous steroids in serum , veterinary drugs in sewage , polybrominated diphenyl ethers in fish and in clinical analysis . The median LOQ value determined from the high-resolution mass spectrometry measurements was approximately one order of magnitude higher than the LOQ determined from the lowresolution measurements. Thus, a certain proportion (about 40% of the detected analytes) of the extremely low-abundance analytes in the naturally contaminated urine samples were not quantified in the HRMS analyses. In addition, HRMS also detected fewer analytes below the LOQ and above the limit of detection, which is about a third of the LOQ, compared to QQQ. However, the concentrations of the missed analytes were primarily low. Excluding compounds where the respective concentration was below the LOQ in the QQQ (approx. one third of the cases), the median concentration of analytes detected in QQQ but not in the high-resolution data was 0.15 ng/mL. The majority (90%) of the undetected chemicals were in the sub-ng/mL range or even lower. Most of the individual analytes were observed in at least one sample in the HRMS measurement (75%), and it was mainly the low-abundance contaminants below the LOQ in QQQ that were usually not detected in HRMS. The ultra-low LOQs of the QQQ approach might discover additional low-level contaminants and improves the extent of quantitative data and chronic background exposures. Nevertheless, screening for chemicals of interest and unknowns, the primary purpose of HRMS, is feasible for many chemicals.