The extraction efficiencies from the urine and serum samples were high (median of 93% and 87%, respectively); while recoveries from breast milk were lower (median of 54%). Due to the high fat and protein content of milk, a two-phase extraction protocol was implemented to deplete the organic layer of matrix components. Thus, consistent with other reports (Braun et al. 2018 ), the expectation was that to a certain degree the polar analytes may be lost in the aqueous phase. Detailed results of the analytical validation are reported in Supplementary Table and Supplementary Table . For most compounds, the limits of detection and quantitation (LODs/LOQs) were in the range of 0.001-0.1 ng mL -1 .