Acetyl isoniazid

Reference standards for isoniazid (97.1 % purity), acetyl-isoniazid (98.0 % purity), isoniazid-d4 (INH-d4; used as internal standard 98.0 % purity), and acetyl-isoniazid-d4 (AcINH-d4; used as internal standard 98.0 % purity) were purchased from Toronto Research Chemicals (TRC).
Ammonium acetate and dimethyl sulfoxide (DMSO) (high purity grade) were purchased from Sigma-Aldrich (Darmstadt, Germany). Ammonium bicarbonate (high purity grade) was purchased from Acros organics (Geel, Belgium). Acetonitrile and methanol (LC-MS grade) were purchased from Honeywell (Burdick and Jackson, Muskegon, Michigan), and LC-MS grade water was produced in-house using the Milli-Q water purification system (Merck Millipore, Darmstadt, Germany). Strata X 33 µm Polymeric Reversed Phase 200 mg/3mL solid phase extraction (SPE) columns were purchased from Phenomenex (California, United States).

Acetyl isoniazid, deacetyl rifabutin, desacetyl rifampicin, ethambutol, isoniazid, pyrazinamide, rifabutin and their deuterated internal standards: Acetyl isoniazid-d4 (isotopic purity: 99.4%), deacetyl rifabutin-d7 (isotopic purity: 98.5%), desacetyl rifampicin-d3 (isotopic purity: 99.6%), ethambutol-d4 (isotopic purity: 99.1%), isoniazid-d4 (isotopic purity: 99.3%), pyrazinamide-15 N,d3 (isotopic purity: 99.5%), and rifabutin-d7 (isotopic purity: 97.2%), were purchased from Toronto Research Chemicals (North York, Canada). Rifampicin reference material was purchased from the United States Pharmacopeia (Rockville, United States) and its deuterated internal standard, rifampicin-d3 (isotopic purity: 98.9%), was purchased from Toronto Research Chemicals (North York, Canada). Ammonium acetate, ascorbic acid, and dimethyl sulfoxide were purchased from Sigma-Aldrich (Darmstadt, Germany). Formic acid and ammonium bicarbonate were purchased from Merck (Darmstadt, Germany) and Acros Organics (Fair Lawn, United States), respectively. Acetonitrile and methanol were purchased from Honeywell (Charlotte, United States). LC-MS/MS grade millipore water was produced in-house (Merck-Millipore, Germany).