Investigation Of Tandem Mass Spectrometric Behavior Of Kaempferide By Online Collision Energy-Resolved Mass Spectrometry-Structural Calculation

Regarding tandem mass spectrometry ( MS/MS ) , the theory of the transition from precursor ion to product ion is actually chemical bond dissociation in gas phase resulted from the collision between ions and collision gas molecules with high energy. It is feasible to observe the generation and disappearance of ions via gradually varying the collision energy, which is the mechanism of online collision energy-resolved mass spectrometry ( ER-MS ) . Afterwards, the assignment of fragmentation pathways to the ions-of-interest can be achieved through combining online ER-MS and structural calculation. In current study, the application of online ER-MS towards in-depth clarification of tandem mass spectrometric pattern was illustrated by employing kaempferide as a representative case. Under positive ionization mode , the precursor ion , actually the protonated molecular ion ( [ M+H ](+)) , was generated at m/z 301. 0712 in MS1 spectrum , which resulted in primary product ions , such as m/z 286. 0518 , 272. 0454 , 165. 0155 , 161.0573, 153. 0192 and 139. 0381 in MS2 spectrum. To clarify the generation of m/z 161. 0573 , a precursor > product ion transition was subsequently constructed as m/z 301 > 161. A set of pseudo-ion transitions ( PITs ) was afterwards derived , and assigned a batch of progressive collision energies. The peak areas of all PITs were acquired under multiple reaction monitoring mode on triple quadrupole mass spectrometer ( QqQ-MS ) , and normalized within the PITs set to construct the breakdown graphs. Except for m/z 301 > 161 , the breakdown graphs of the other ion transitions fitted for Gaussian curve. " M " -type breakdown graph consisting of two Gaussian curves was observed for m/z 301 > 161. Following structural calculation, the former Gaussian curve was primarily generated by C-ring hetero-ring fission ( HRF) at 1 ,4-bond coupled with CH4 neutral loss, whereas the latter one corresponded to C-ring RDA fission at 0, 4-bond coupled with CH3 OH neutral loss. Above all, the combination of online ER-MS and structural calculation is able to provide meaningful information for the in-depth clarification of tandem mass spectrometric patterns of chemical compounds.