For the RP measurements, the gradient was as follows: 0 -1 min, constant flow at 10% B; 1 -10 min, increase to 70% B; 10 -11 min, rise to 100% B and 13.5 -15 min, equilibration at 10% B. A hydrophilic interaction liquid chromatography column (HILIC), SeQuant®ZIC®-pHILIC (5 μm, polymeric, 150 x 2.1 mm) was operated with the following gradient: 0-1 min, constant flow at 75% B; 1-6 min, linear decrease to 50%; 6-7 min, drop to 30% B; 7-11 min, constant flow at 30%; 11-15 min, equilibration at 75% B. Both columns were at 40 °C and a flow rate of 0.3 mL/min was set. The Acquity BEH Amide was operated with a slightly different gradient as follows: 0-2 min, constant at 80% B; 2-8 min decrease to 40% B; 8-10 min, constant at 40% B and 10-15 min, equilibration at 80% B. Both capillaries were connected with a T-piece to mix the effluents before introduction into the ESI source of the mass spectrometer (Figure ). As needle wash, 75% ACN was used for the HILIC measurement, while H2O:ACN: MeOH (2:1:1,v:v:v) was applied for the RP run. Measurements were conducted in fast polarity-switching full scan mode on a Q Exactive HF quadrupole-Orbitrap mass spectrometer. The settings of the ESI interface were as follows: sheath gas, 48 au; auxiliary gas, 11 au; sweep gas flow, 2 au; capillary voltage, 3.5 kV (positive), 2.8 kV (negative); capillary temperature, 260°C; auxiliary gas heater, 410°C. The scan range was from 65 to 900 m/z. For full scan only measurements, the resolution was set to 60,000 with an AGC target (automatic gain control) of 1 x10 6 and a maximum injection time of 200 ms. The instrument was calibrated before the analysis. Following the optimization of chromatographic conditions, the most suitable RP/HILIC combination was selected. Consequently, the parameters mentioned above for combination two (Figure ) were applied for the sample measurement. A mixture of both effluents entered the mass spectrometer via the ESI source (Figure ). For analyses with data-dependent MS2, a resolution of 60,000 with an AGC target of 1x10 6 and a maximum injection time of 100 ms were chosen for the full scan. The settings for the MS2 collection were the following: resolution, 30,000; AGC target, 1 x 10 5 ; maximum injection time, 50 ms, loop count, 10; isolation window, 1.0 m/z; normalized collision energy, 30 eV; minimum AGC, 8x10 3 ; dynamic exclusion, 4 s. Iterative exclusion lists were generated with IE-Omics . The urine samples from Nigeria and Austria were analyzed in randomized order. )) was used for targeted analysis and quantification. An internal standard correction was performed. If no internal standard was included for the specific analyte, the internal standard with the closest retention time was selected as a surrogate standard for normalization (Table ). For endogenous metabolites excluding estrogens the peak originating from the HILIC column was used, while xenobiotics and endogenous estrogens were evaluated with the RP peak. The linear calibration curves (Table ) were 1/x weighted. Matrix matched calibration for urine and plasma was performed and the corresponding calibration curves were used for the quantification of xenobiotics and human estrogens. However, endogenous metabolites were, as expected, frequently highly abundant in the matrices. Therefore a solvent calibration was applied for endogenous metabolites (excluding estrogens). The creatinine levels were quantitated with a one-point calibration based on the creatinine level in the SRM3672 (734 mg/L). The limits of detection (LODs) were determined based on the EURACHEM guideline as three times the standard deviation of multiple injections of a low-concentrated standard (n=6) divided by the square root of the number of replicates. For the limit of quantification (LOQ), the tenfold standard deviation was used. The recoveries were calculated by dividing the spiked concentration by the measeasured concentration multiplied by 100. The expected concentration level in the spiked samples used for recovery calculation corresponded to standard level 6. Spearman correlation was calculated for compounds positive in at least 20% of all Nigerian samples with R and plotted with the corrplot package (version 0.90) ). MetaboAnalyst 5.0 ) was used for pathway analysis. A hypergeometric test was selected as an enrichment method and for topology analysis relative-betweenness centrality. The pathway library was Homo sapiens (KEGG).