Abundance Stability Study of α-H Cleavage Induced by Free Radical Center Based on Linear Ion Trap Mass Spectrometry / 中国药学杂志

ABSTRACT

OBJECTIVE: To study the response stability of free radical center-induced α-H cleavage on linear ion trap mass spectrometry (LTQ-MS), and discuss the interaction mechanism in ion trap and the effects of hydrogen and deuterium hybrid loss on quantitation precision. METHODS: The special cleavage mode of D6-ornithine lactam was used to distinguish different α-H cleavage, and the factors that might affect the abundance stability were inferred by mechanism discussion and falsification. RESULTS: The quantitation precision of ion pairs with only hydrogen loss(115.1→97.1;121.1→103.1) and threonine instead of D6-ornithine lactam (115.1→70.1;120.1→74.0)was significantly better than that of ion pairs involving hydrogen-deuterium hybrid loss(115.1→70.1;121.1→75.1). When 115.1→70.1;121.1→75.1 were used, the quantitation precision of tandem quadrupole mass spectrometry was significantly better than that of LTQ-MS. CONCLUSION: The instability of ion abundance, the effect of quality discrimination and the effect of ion concentration saturation are not significant factors affecting the stability of LTQ detection signal. Combined with the fragmentation characteristics of D6-ornithine lactam and Matthew′s equation, it is proposed that the space charge in the trap is the main reason for the instability of the detection signal.