title: Isolation and identification of process impurities in trimethoprim drug substance by high-performance liquid chromatography, atmospheric pressure chemical ionization liquid chromatography/mass spectrometry and nuclear magnetic resonance spectroscopy.
abstract: Twenty-two lots of recently synthesized trimethoprim drug substance, from five different manufacturers, in three different countries of origin, China, Israel and the United States, were investigated for the presence of impurities. A liquid chromatographic system, using gradient elution, and a mobile phase consisting of 0.25% TEA/0.1% formic acid (pH 5.8)--acetonitrile, was used to separate and detect two significant, recurring impurities in trimethoprim drug substance. The two impurities were isolated by preparative liquid chromatography and identified, using a combination of liquid chromatography/mass spectroscopy and nuclear magnetic resonance, as 2,4-diamino-5-(4-ethoxy-3,5-dimethoxybenzyl) pyrimidine and 2,4-diamino-5-(3-bromo-4,5-dimethoxybenzyl) pyrimidine. These impurities were not detected by the compendial method and were present at significant levels in 17 of the lots tested. Total impurity concentrations were in the range of 0.1-2.1%.
authors.affiliation: Department of Health and Human Services, Food and Drug Administration, Brooklyn, NY 11232-1593, USA.
authors.forename: G J
authors.initials: GJ
authors.lastname: Lehr
authors.forename: T L
authors.initials: TL
authors.lastname: Barry
authors.forename: G
authors.initials: G
authors.lastname: Petzinger
authors.forename: G M
authors.initials: GM
authors.lastname: Hanna
authors.forename: S W
authors.initials: SW
authors.lastname: Zito
mesh_terms: D001274:Atmospheric Pressure; D002681:China; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D004340:Drug Contamination; D004348:Drug Labeling; D005021:Ethylamines / Q000737:chemistry; D005561:Formates / Q000737:chemistry; D007557:Israel; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry / Q000295:instrumentation; D011358:Product Surveillance, Postmarketing; D011743:Pyrimidines / Q000032:analysis / Q000302:isolation & purification; D014295:Trimethoprim / Q000032:analysis / Q000737:chemistry*; D014481:United States
chemical_list: C405222:2,4-diamino-5-(3-bromo-4,5-dimethoxybenzyl)pyrimidine; C405210:2,4-diamino-5-(4-ethoxy-3,5-dimethoxybenzyl)pyrimidine; D005021:Ethylamines; D005561:Formates; D011743:Pyrimidines; D014295:Trimethoprim; C016162:triethylamine