天然同位素信息在多级质谱裂解规律解析中的应用——以磺胺类化合物为例

Elucidation Tandem Mass Fragment Pathway by Isotopic Ion Ratio and Accuracy Mass Measure——An Example in Sulfanilamide

为了更好的对多级质谱裂解信息进行解析,本研究在多级质谱中应用同位素峰信息进行分子式确证。使用二级质谱中同位素峰丰度比例和峰形信息,对化合物的质谱裂解碎片分子组成进行预测和推断。通过改变LTQ Orbitrap XL仪器的离子阱参数,将isolation width设为6u,使目标母离子的最轻同位素峰和两个较重同位素峰共同裂解,报道了在二级质谱中获得目标化合物的同位素信息,并使用这些信息对化合物裂解碎片进行推测。以磺胺甲基嘧啶为例,通过同位素信息提供的丰度比和峰形信息,对主要裂解碎片离子进行解析,大多数结果与文献报道的裂解途径一致,但对于磺胺甲基嘧啶二级质谱中m/z65的碎片离子,与已发表的文献报道不同,通过高分辨质谱和同位素丰度比的佐证,重新对其进行了解析,证明这是一个不含硫元素的子离子。结果表明,该方法能够有效减少分子式推测过程中产生的错误备选结果,可以为多级质谱的解析提供更准确的依据。

MS/MS isotope ratio and accuracy mass measure were used to further confirm the elemental composition and structural information of molecular formula by performing on an LTQ/Orbitrap. The light and heavy isotopes of target parent ion were detected when set- ting the ion trap＇s isolation width at 6 u. The MS/MS isotope ratio and accuracy mass measure were used to elucidate the fragments pathway. Sulfamerazine was used as an exam- ple, most of the fragmentations were analyzed by isotopic abundance ratio and peak shape information, the result is as same as literature reported. However, the fragment ion at m/z 65 is different from previous report. According to it accuracy mass measure and isotope abundance ratio, there is no S atom in this ion. The result shows that the proposed isotope distribute fragmentation method is a powerful trick to ：provide large amounts of the necessa- ry elemental composition to the fragment news of compounds.