A gas chromatographic/mass spectrometric study of the trimethylsilylation of ethambutol and a tablets assay method based on the trimethylsilyl derivative.

The trimethylsilylation of ethambutol base and ethambutol hydrochloride was studied by means of GC/MS. The derivatisation is shown to proceed in two distinct steps, and the second derivative is identified, by both chemical ionisation and electron impact Ms, and the di-trimethylsilyl ethambutol. Most of the major mass fragments observed are assigned. A tablets assay method, based on the direct trimethylsilylation of ethambutol hydrochloride in tablets, is also described. It is simple, rapid, and unaffected by the presence of the common excipients in the tablets.