Benzoylecgonine

Cerilliant® certified reference material solutions (1 mg/ml of morphine, amfetamine, benzoylecgonine, diazepam and THC solutions in methanol; 1 mg/ml cocaine solution in acetonitrile) and deuterated analogues (100 μg/ml d₃‐morphine, d₅‐amfetamine, d₃‐benzoylecgonine, d₅‐diazepam and d₃‐THC solutions in methanol; 100 μg/ml d₃‐cocaine solution in acetonitrile) were purchased from Sigma Aldrich (Dorset, UK). The purity of all reference solutions was greater than 99%. Mucin (bovine mucin from submaxillary glands), potassium thiocyanate, calcium chloride dihydrate, magnesium chloride hexahydrate, Tetronic® 90R4 and Tween® 20 were purchased from Sigma Aldrich (Dorset, UK). Potassium chloride, potassium dihydrogen phosphate, sodium chloride, sodium azide, sodium hydrogen carbonate, urea, ammonium acetate and glacial acetic acid were purchased from Fisher Scientific (Loughborough, UK). All reagents were of analytical reagent grade with the exception of Tween® 20 which was BioXtra grade. LC–MS grade acetonitrile was purchased from VWR (Lutterworth, UK). Deionised water was obtained at 18 MΏ.cm⁻¹ resistivity from Elga Purelab Flex water dispenser (High Wycombe, UK).