## 2 Materials and Methods
### Sampling Kits and Water Collection Protocol  
The sampling kits were designed to simplify logistics so that a large number of locations could be sampled with a minimum of effort. As the sample injection volume for the developed method was only 100 \(\upmu\)L, the standard collection volume was set at 10 mL of sample water. Samples were collected in duplicate to provide a backup sample in case of breakage of the primary sample container during shipment. Each sampling kit therefore contained: 20 amber glass vials (15 mL) (for collection of 10 samples in duplicate), two ice packs, 10 polypropylene syringes (24 mL), 10 glass microfiber filters (0.7-\(\upmu\)m pore size), a 500-mL stainless-steel bucket with 10-m long nylon cord attached, material to collect a field blank quality-control (QC) sample with LCMS-grade water, a standardised collection log and sample labels. Kits weighed 2.25 kg and were able to fit into a 34.5 \(\times\) 21 \(\times\) 14.5 cm box (approximately the size of a shoe box). The sample collection protocol, including storage and shipping procedures, was included with the sampling kit and instructional videos were also provided online (<[[https://youtu.be/HeZ?xox](https://youtu.be/HeZ?xox)]([https://youtu.be/HeZ?xox](https://youtu.be/HeZ?xox)))XhM> and <[[https://youtu.be/PLyCNcVCKdc](https://youtu.be/PLyCNcVCKdc)]([https://youtu.be/PLyCNcVCKdc](https://youtu.be/PLyCNcVCKdc))>). At each location, the bucket (included with each kit) was \begin{table}
\begin{tabular}{l c c} \hline \hline
**Therapeutic Class** & **Compound** & **Associated Internal Standard** \\ \hline \multirow{8}{*}{Antidepressant} & Amitriptyline & Amitriptyline D3 \\  & Ctalopram & Ctalopram D6 \\  & Desvenlafaxine & Desvenlafaxine D6 \\  & Fluoxetine & Atrazine D5 \\  & Sertalazine & Sertalazine D3 \\  & Venlafaxine & Venlafaxine D6 \\  & Norfluoxetine & Norfluoxetine D6 \\ \hline \multirow{8}{*}{Antifungal} & Clotrimazole & Atrazine D5 \\  & Fluoxazole & Atrazine D5 \\  & Itraconazole & Itraconazole \\  & Ketoconazole & Atrazine D5 \\  & Miconazole & Atrazine D5 \\  & Thhaethoralazole & Atrazine D5 \\ \hline \multirow{8}{*}{Antihistamine} & Cetririarine & Atrazine D6 \\  & Diphenhydramine & Diphenhydramine D3 \\  & Fexofenadine & Atrazine D5 \\  & Ketotifen & Atrazine D5 \\  & Loradaine & Atrazine D5 \\ \hline \multirow{2}{*}{Anthhyperglycemic} & Metformin & Metformin D6 \\  & Sitagliptin & Sitagliptin D4 \\ \hline Antimalarial & Artemisinin & Atrazine D5 \\ \hline Antiviral/-retroviral & Nevirapine & Atrazine D5 \\  & Oseltamivir & Atrazine D5 \\ \hline \multirow{2}{*}{Benzodiazepepine} & DiazepD & DiazepD5 \\  & Oaxazepam & Oaxeepam D5 \\  & Temazepam & Temazepam D5 \\ \hline \multirow{2}{*}{Beta-blocker} & Atenol & Atenol D7 \\  & Propranolol & Propranolol D7 \\ \hline \multirow{2}{*}{Calcium channel blocker} & Diliaizem & Diliaizem D3 \\  & Verapamil & Verapamil D7 \\ \hline \multirow{2}{*}{Diuretic} & Triamterene & Triamterene D5 \\ \hline \multirow{2}{*}{Histamine H\({}_{2}\) receptor antagonist} & Cimetidine & Atrazine D5 \\  & Ranitidine & Atrazine D5 \\ \hline \multirow{4}{*}{Opioid pain medication} & Codeine & Codeine D6 \\  & Hydrocodeone & Hydrocode D3 \\  & Triamadol & Atrazine D5 \\ \hline Oral contraceptive & Noreshorenne & Atrazine D5 \\ \hline Selective estrogen receptor modulator & Raloxifene & Raloxifene D4 \\ \hline \multirow{2}{*}{Stimulant} & Caffeine & Atrazine D5 \\  & Cotinine & Cotinine D3 \\  & Nicotine & Atrazine D5 \\ \hline \(\beta\)2 adrenergic receptor agonist (anti-asthma) & Salbutamol & Salbutamol D9 \\ \hline \hline \end{tabular}  
* Used in animal husbandry.  
\end{table} 
Table 1: _Cont._rinsed three times with native sample water prior to collection. Following sample collection, 20 mL of sample water was aspirated into the syringe, and the syringe filter was then attached and primed with 5 mL of sample water. Then, 5 mL of filtrate was used to rinse out a 15-mL vial prior to dispensing the remaining 10 mL of filtrate into the glass vial.