Ammonia solution 25

Formic acid (FA) and analytical reference standard of Lid and Ket were obtained from Sigma Aldrich (Buchs, Switzerland). Dex was obtained from Tokyo Chemical Industry (Tokyo, Japan). Acetonitrile (ACN) and water were purchased from Merck (Massachusetts, USA) and were of LC-MS grade. HPLC vials, screwcaps and inlets were purchased from BGB (Boeckten, Switzerland).
Hydrochloride acid, EDTA 0.1 M (Titrisol^® Triplex III) and calcium carbonate were obtained from Merck (Massachusetts, USA), ammonia solution 25% from VWR Chemicals (Pennsylvania, USA) and ammonium chloride from Sigma Aldrich (Buchs, Switzerland). These substances were used for titration of magnesium sulfate.
For all experiments, Gilson pipettes and Gilson DIAMOND tips were used (Mettmenstetten, Switzerland). pH meter was calibrated using commercially available standards (ROTI^® Calipure) from Carl Roth GmbH (Karlsruhe, Germany).

Cotinine (COT), trans-3-hydroxycotinine (OH-COT), cotinine-d3 and trans-3-hydroxycotinine-d3 were obtained from LGC Standards (Molsheim, France). Caffeine, ibuprofen, methadone, morphine, pseudoephedrine, codeine, cocaine, clomipramine, propranolol and Δ-9-tetrahydrocannabinol analytical reference standards presented in Methanol were obtained from Cerilliant (Sigma-Aldrich, Saint-Quentin-Fallavier, France). Potassium dihydrogen phosphate and dipotassium hydrogen phosphate were obtained from Sigma-Aldrich (St Louis, MO, USA). Methanol, hexane, isopropanol were of analytical grade and were obtained from Merck (Darmstadt, Germany). Sterile water was obtained from Fresenius (Sevres, France). Ammonia solution 25% was purchased from VWR (Fontenay-sous-Bois, France). Hydrochloric acid 0.2 m was obtained from VWR (Fontenay-sous-Bois, France). Clean Screen SPE columns 200 mg were purchased from UCT (Bristol, PA, USA). The derivatizing agent utilized was bis(trimethylsilyl)trifluoroacetamide (BSTFA) + 1% trimethylchlorosilane (TMS) (Sigma-Aldrich, Saint-Quentin-Fallavier, France).