Positive secondary-ion mass spectra and thin-layer chromatography/mass spectrometry of phenothiazine drugs

The positive secondary-ion mass spectra of phenothiazine drugs contain abundant protonated molecules and structurally informative fragment ions that are characteristic of the N-substituent. Because the secondary-ion current is carried by a few characteristic ions, selected-ion monitoring is used with chromatographic separation for the determination of these drugs in mixtures. Drugs are extracted in situ from thin-layer chromatograms, and the secondary-ion mass spectra are obtained without destruction of the chromatograva. The spectra are dependent upon the solvent used and not the nature of the underlying chromatographic matrix. Spatially-resolved selected-ion monitoring of the protonated molecule provides the x-y spatial profiles of the sample in the chromatogram. Extended irradiation leads to a beam-induced tailing that alters the profile.