Takahashi S
Biomed Environ Mass Spectrom. 1987 Jun;14(6):257-61. doi: 10.1002/bms.1200140603.
This study identified the reason for the poor quantification of lormetazepam-TMS (1) using negative ion chemical ionization with lormetazepam-1,1,1-2H3-TMS (2) as an internal standard. Mass spectra of lormetazepam and its deuterium labelled compounds determined at various ion source temperatures (100-250 degrees C) gave almost the same behaviour for 1 and lormetazepam-3',4',5',6'-2H4-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.
本研究确定了以洛美他嗪 -1,1,1-2H₃ -TMS（2）作为内标，采用负离子化学电离法对洛美他嗪 -TMS（1）进行定量分析结果不佳的原因。在不同离子源温度（100 - 250℃）下测定的洛美他嗪及其氘代化合物的质谱图显示，1和洛美他嗪 -3',4',5',6'-2H₄ -TMS（3）表现出几乎相同的行为，但2表现不同，这表明定量分析结果不佳是由于同位素效应。1和3的基峰离子流比率与离子源温度无关，但1和2的基峰离子流比率随离子源温度显著变化，这一发现证实了上述结论。在分子离子的质量碎片谱中也观察到了这种现象，尽管程度比上述碎片的情况要小。在正离子化学电离和电子轰击电离模式下，均未出现同位素效应，因为没有相应的碎片会导致同位素效应。
