6 acetylmorphine

All model compounds were purchased from Sigma-Aldrich (St. Louis, MO, USA), including metabolites (glucose and inositol), controlled narcotics (codeine, hydrocodone, 6-acetylmorphine, naloxone, morphine, and norcodeine), and isomers (para-/meta-/ortho-aminobenzoic acid). D₂O (99.9 atom % D), methanol (99.9%), deionized ultra-filtered water, ammonium hydroxide, and glacial acetic acid (99.7%) were all obtained from Fisher Scientific. Polymethyl methacrylate (PMMA) was purchased from Titan Scientific Co. Ltd. (Shanghai, China), and multi-walled carbon nanotubes (MWCNT, ID 2–5 nM, OD < 8 nM, length 10–30 μM) were purchased from J&K Scientific Ltd. (Beijing, China).

All the standard molecules used in the study were purchased from Sigma-Aldrich (St. Louis, MO, USA): morphine, morphine-3-glucuronide, morphine-6-glucoronide solutions (1.0 mg/mL in methanol each standard) and 6-acetylmorphine (1.0 mg/mL in acetonitrile standard solution). Deuterated internal standards (ISs) were purchased from Sigma-Aldrich as well: morphine-D₃ (1.0 mg/mL in methanol standard solution), 6-acethylmorphine-D₃ (1.0 mg/mL in acetonitrile), morphine-3-glucuronide-D₃ (100 µg/mL in methanol with 0.05% of NaOH) and morphine-6-glucuronide-D₃ (100 µg/mL methanol/water (1:1, v/v)). Solvents used in the extractive processes were purchased from Sigma-Aldrich (methanol, hydrochloric acid, chloroform, dichloromethane and ethyl acetate) and VWR Chemicals (Radnor, PA, USA) (acetone, acetonitrile, isopropanol and n-hexane). Buffer pH 6.88 solution was purchased from PanReac (Barcelona, Spain). For histological inclusions, absolute ethanol and xylene substitute were purchased from VWR Chemicals and high fusion point paraffin pearls Histowax® were purchased from International Medical Products (Brussel, Belgium).