Acetaminophen, amoxicillin·3H2O, azithromycin, diclofenac sodium, ethambutol diHCl, fluconazole, isoniazid, levofloxacin, linezolid, metformin, sulfamethoxazole and trimethoprim were purchased from Sigma–Aldrich (St Louis, MO, USA). Bedaquiline, ciprofloxacin, dolutegravir, efavirenz and rifampicin were purchased from Alsachim (Illkirch, France). Clofazimine, d -cycloserine, ethionamide and prothionamide were obtained from Toronto Research Chemicals (Ontario, Canada). Pyrazinamide was acquired from Honeywell Fluka (Bucharest, Romania). All reference materials were of ≥98% purity. Ultrapure water (resistivity >15 MΩ·cm at 25°C) was obtained from a Milli-Q Advantage A10 system (Millipore Corporation, Billerica, MA, USA). Absolute methanol of UPLC–MS grade was acquired from Biosolve BV (Valkenswaard, the Netherlands).
Separate stock solutions were used for the preparation of the calibration standards and the quality control (QC) samples. For all experiments, the total volume of (diluted) stock solutions added to filtered drug-free saliva never exceeded 5% (v/v). Calibration standards and QC samples were portioned into vials and stored at −20°C. Vials were discarded after a day of use.
Separate stock solutions were used for the preparation of the calibration standards and the quality control (QC) samples. For all experiments, the total volume of (diluted) stock solutions added to filtered drug-free saliva never exceeded 5% (v/v). Calibration standards and QC samples were portioned into vials and stored at −20°C. Vials were discarded after a day of use.