Gas chromatographic-mass fragmentographic determation of "steady-state" plasma levels of imipramine and desipramine in chronically treated patients.

A sensitive and specific method for the simultaneous determination of imipramine and desipramine in the blood plasma of depressed patients under treatment that involves separation by gas chromatography and detection by mass fragmentography is described. Concentrations were determined by focusing the mass spectrometer upon the ions at m/e 280 and 235 for imipramine and 308, 236 and 114 for desipramine (N-acetyl derivative), while promazine was used as the internal standard (ions at m/e 284 and 238). Determinations are possible at levels as low as 10 ng/ml in plasma.