Acetaminophen methyl d3

The 11 pharmaceuticals studied are classified following their Anatomical Therapeutic Chemical Classification code (ATC). They all were purchased from Sigma-Aldrich (St. Louis, MO, USA) with a purity range of 98–99%. Furthermore, atenolol-d7, lidocaine-diethyl-d10 and acetaminophen-methyl-d₃ were acquired also at Sigma-Aldrich and were used as internal standards. HPLC grade methanol and acetonitrile (ACN) were supplied by VWR Chemicals (Leuven, Belgium). Ammonium formate (NH₄COOH) and ammonium hydroxide (NH₄OH) were supplied by Sigma-Aldrich (St. Louis, MO, USA). Hydrochloric acid 37% (HCl) and formic acid (HCOOH) were purchased from Fisher Scientific (Bridgewater, MA, USA). Ultra-pure Milli-Q water was obtained through a Millipore purification system (Millipore, Bedford, MA, USA). Standard stock solutions were prepared in amber glass vials at a concentration of 1000 mg L⁻¹ in methanol, and working solutions were prepared between 1 and 2500 µg L⁻¹ in 90% of Milli-Q water and 10% of methanol.

Thirty-three standards of 98–99% purity were purchased from Sigma-Aldrich (St. Louis, MO, USA) and ten from Santa Cruz Biotechnology (Santa Cruz, CA, USA). Acetaminophen-methyl-d₃ (Sigma-Aldrich) was used as internal standard. All the target compounds and the main uses and category according to the ATC code are indicated in Table 2. Stock standard solutions were prepared at a concentration of 1000 ng µL⁻¹ and working solutions at 1–10 ng µL⁻¹, all in methanol.
Methanol (MeOH) and HPLC water (LiChrosolv grade) were supplied by Merck (Darmstadt, Germany). Formic acid (HCOOH), hydrochloric acid 37% (HCl), and ammonium acetate (NH₄OAc) were supplied by Sigma-Aldrich (St. Louis, MO, USA) and acetonitrile (ACN) was supplied by Fisher Scientific Chemical (Bridgewater, NJ, USA).