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

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 setting 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 example, 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 its 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 necessary elemental composition to the fragment news of compounds.