Tramadol

Chemicals LC-MS grade water was purchased from Huberlab (Aesch, Switzerland); methanol was purchased from VWR (Darmstadt, Germany); formic acid was purchased from Sigma-Aldrich (Buchs, Switzerland). Benzoylecgonine, norcocaine, cocaine, cocaine-d3, methylecgonine, cocaethanol, tramadol, O-desmethyltramadol, and N-desmethyltramadol were purchased from Lipomed AG (Arlesheim, Switzerland). A pool of human urine was made using nine anonymous donors and was stored at -20 °C prior to analysis.
Computer-aided design and 3D printing 3DP-OPP and other models were designed in Autodesk Fusion360 software (San Rafael, USA). Source files in .stl format containing various parts are available in the ESI. † A FormLabs Form 2 SLA printer (Artsupport GmbH, RümLang, Switzerland) was used for printing a 3DP-OPP with High Temp resin due to its compatibility with methanol and a printing liquid handler tool with Clear resin because it is more flexible and resistant to impact. The model was oriented at 45°t owards the table and sliced at 0.05 mm resolution using the PreForm software (FormLabs, Somerville, USA). The density of the supports was set to 0.60 and the point size was set to 0.50 mm. An X400CE FDM printer and PLA filament (German RepRap GmbH, Feldkirchen, Germany) were used for printing other parts.