## 3 Results and Discussion
### Implication for Future Research  
The method presented here offers the first truly transferable sampling, shipping and mass spectrometry protocol for use in global monitoring campaigns. Potential applications include research extending the spatial and temporal resolution of published data on API contamination of water globally, applications related to antimicrobial resistance selection, as well as the potential for further method development enabling determination of other aquatic contaminants including persistent organic pollutants and metals. The small size of the sample vials and corresponding shipping packages and ease of sample collection may encourage the incorporation of citizen science in future API research. Fast, easy and cheap analytical methods are key to advancing the understanding of exposure to chemical contaminants via water and this method offers a clear step forward. Supplementary Materials: Supplementary tables and figures are available online at: [[http://www.mdpi.com/2076-3417/9/7/1368/s1](http://www.mdpi.com/2076-3417/9/7/1368/s1)]([http://www.mdpi.com/2076-3417/9/7/1368/s1](http://www.mdpi.com/2076-3417/9/7/1368/s1)). Figure S1: Map of the sampling locations along Muddy Creek with GPS coordinates and sample site description, Table S1: Mass spectrometer conditions and target ions with precursor, transition 1 (T1) for quantitation and transition 2 (T2) for confirmation mass-to-charge ratios, collision energy and retention times, Table S2: Concentrations of the 15 calibration levels used in this method with the volumes and concentrations of mixed stock solutions used to create final calibrations with an equal amount of organic solvent in each, Table S3: Stability of monitored chemicals over 2 and 7 days at three temperatures, Table S4: Concentrations of 30 medicinal chemicals quantified in Muddy Creek (Iowa, USA) by the USGS (Central Midwest Water Science Center, Iowa City, Iowa) and University of York (York, UK), Table S5: Linearity (n = 3) and relative standard deviation (%) of both Intra-day repeatability (n = 6) and intermediate precision (n = 6) for the 61 APIs in the presented method validation with cells shaded in red indicating RSD > 20%, Table S6: Recovery (%) of 61 APIs from LCMS-grade water (n = 10) with cells shaded in green indicating a recovery between 60-130%, Table S7: Recovery (%) of 61 APIs from drinking (tap) water obtained from the University of York (n = 10) with cells shaded in green indicating a recovery between 60-130%, Table S8: Recovery (%) of 61 APIs from surface water obtained from the River Ouse in York City Centre, UK (n = 10) with cells shaded in green indicating a recovery between 60-130%, Table S9: Recovery (%) of 61 APIs from wastewater treatment plant (WWTP) effluent obtained from a WWTP in Barnsley, UK (n = 10) with cells shaded in green indicating a recovery between 60-130%, Table S10: Recovery (%) of 61 APIs from wastewater treatment plant (WWTP) effluent obtained from a WWTP in Barnsley, UK (n = 10) with cells shaded in green indicating a recovery between 60-130%, Table S11: Limits of Detection (LOD) and Quantification (LOQ) determined in respective matrices, Table S12: Concentrations, in ng/L, of all 61 APIs determined by the method presented in this paper found in the Muddy Creek (North Liberty, Iowa, USA). **Acknowledgments:** The authors would like to thank [PERSON] and [PERSON] (USGS Central Midwest Water Science Center) for the collection of stream and WWTP effluent samples at the Muddy Creek sites and programmatic support by the Toxic Substances Hydrology Program of the USGS Environmental Health Mission Area. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. The authors also acknowledge the York CoEMS which was created thanks to a major capital investment through Science City York, supported by Yorkshire Forward with funds from the Northern Way Initiative, and subsequent support from EPSRC (EP/K039660/1; EP/M028127/1).