基于线性离子阱质谱的自由基中心诱导α-H断裂丰度稳定性研究

目的研究线性离子阱质谱(LTQ-MS)对自由基中心诱导α-H断裂的响应稳定性,探讨离子阱内相互作用机制及氢氘混杂丢失对定量精密度的影响。方法利用D6-鸟氨酸内酰胺的特殊碎裂方式区分α-H断裂,通过机制探讨推测可能影响丰度稳定性的因素。结果仅丢失氢的离子对(115.1→97.1;121.1→103.1)和苏氨酸替代D6-鸟氨酸内酰胺的离子对(115.1→70.1;120.1→74.0)精密度均显著优于涉及氢氘混杂丢失的离子对(115.1→70.1;121.1→75.1)。采用115.1→70.1;121.1→75.1时,串联四级杆质谱精密度显著优于LTQ-MS。结论丰度不稳定、质量歧视效应、离子浓度饱和效应不影响LTQ检测信号稳定性。结合D6-鸟氨酸内酰胺碎裂特点以及马修方程,提出离子阱内空间电荷作用是导致检测信号不稳定的主要原因。

Abundance Stability Study of α-H Cleavage Induced by Free Radical Center Based on Linear Ion Trap Mass Spectrometry

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.