Impurities in halothane: their identities, concentrations and determination

The following impurities arising during the manufacture of a proprietary halothane have been identified by gas chromatographic, mass spectrometric, nmr and infrared techniques: 2-chloro-, 2,2-dichloro-, 2-bromo-, 2,2-dibromo-, 2,2-dibromo-2-chloro- and 2-bromo-2,2-dichloro-1,1,1-trifluoroethanes, 1,1,2-trichloro-1,2,2-trifluoroethane, 1,2-dichloro-1,1-difluoroethane, 2-bromo-2-chloro-1,1-difluoroethylene, bromodichlorofluoromethane, chloroform, trans-2-bromo-1,1,1,4,4,4-hexafluorobut-2-ene and the trans and cis isomers of 2-chloro- and 2,3-dichloro-1,1,1,4,4,4-hexafluorobut-2-enes. Gas chromatographic methods using chlorinated biphenyl, dinonyl phthalate and polyethylene glycol as liquid phases have been developed for their determination at the ppm level.