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Isotope effect in negative ion chemical ionization mass spectrometry of deuterium labelled lormetazepam
Author(s) -
Takahashi Shirô
Publication year - 1987
Publication title -
biomedical and environmental mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 0887-6134
DOI - 10.1002/bms.1200140603
Subject(s) - deuterium , mass spectrometry , isotope , chemistry , ionization , thermal ionization mass spectrometry , ion , radiochemistry , chromatography , physics , nuclear physics , organic chemistry
This study identified the reason for the poor quantification of Iormetazepam‐TMS (1) using negative ion chemical ionization with lormetazepam‐1,1,1‐ 2 H 3 ‐TMS (2) as an internal standard. Mass spectra of lormetazepam and its deuterium labelled compounds determined at various ion source temperatures (100–250°C) gave almost the same behaviour for 1 and lormetazepam‐3′,4′,5′,6′‐ 2 H 4 ‐TMS (3) but a different one for 2, suggesting that the poor quantification was due to an isotope effect. This was confirmed by the findings that the ratios of ion currents of the base peaks of 1 and 3 were independent of the ion source temperature but those of 1 and 2 varied markedly with it. This phenomenon was also observed in the mass fragmentography of the molecular ion, although to a lesser degree than that of the above fragment. In both positive ion chemical ionization and electron impact ionization modes, no isotope effect arose because there was no corresponding fragment to cause the isotope effect.