Chromasolv methanol meoh of lc ms grade

Cyclopropylfentanyl hydrochloride for animal experiments was acquired from Cayman Chemical (Ann Arbor, MI, USA). A stock solution of 1 mg/mL cyclopropylfentanyl in sterile saline was prepared, and 300 µL aliquots were stored at –20 °C. Cyclopropylfentanyl hydrochloride and furanylfentanyl-d₅ for analytical standards were acquired from Cayman Chemical. Cyclopropylnorfentanyl and norfentanyl-d₅ were acquired from Chiron AS (Trondheim, Norway). Chromasolv methanol (MeOH) of LC–MS grade was acquired from Honeywell Riedel-de Haën (Seelze, Germany). Ammonium formate and formic acid (98%) were acquired from VWR International AS (Oslo, Norway). Ethyl acetate, n-heptane, nitric acid, and sodium hydroxide were acquired from Merck (Darmstadt, Germany). Disodium tetraborate decahydrate was acquired from Chemi-Teknik AS (Oslo, Norway). Saline was acquired from Hospira (Lake Forest, IL, USA), whereas sodium heparin was acquired from Thomas Scientific (Thomas Scientific, Swedesboro, NJ, USA). Type 1 water (18.2 MΩ) purified with a Synthesis A 10 milli-Q system from Millipore (Billerica, MA, USA) was employed.