An Ultra-Wide-Band Photodissociation Mass Spectrometry-Spectroscopy System Based On An FT-ICR Mass Spectrometer And Its Application

The diversity and complexity of analytes in chemistry and biology are increasing rapidly in the past years.To achieve the challenging goals,much higher requirements have been put forward on the performance of scientific instruments more than ever.Mass spectrometry has been widely applied as an important characterization method,in which tandem mass spectrometry is of particularly important for studying molecule structures by analyzing fragment ions after activation though different approaches.By combing of different wavelength laser with mass spectrometer,many scientists have carried out research about photodissociation mass spectrometry-spectroscopy studies and have made great achievements in the past several decades.However,the performable coverage range of tunable laser wavelength in separated experiment setups owned by different research groups in the world greatly restricted their corresponding application in molecular structure analysis.An expanded coverage range of tunable laser fulfilled in a single setup will be very important by bringing more systemic spectral and structural information of target molecules.On the other hand,diverse fragments can be obtained with a variety of ion activation methods acting on target ions,while are helpful to understand their structural characteristics and kinetic information deeply.Among many types of mass spectrometers,Fourier transform ion cyclotron resonance(FT-ICR)mass spectrometer is an ideal instrument in tandem mass spectrometry study due to its high-resolution power,excellent ion selection and manipulation capabilities.Aimed with the idea above,this thesis is dedicated to the design and implementation of an ultra-wide band photodissociation mass spectrometry-spectroscopy system based on a FT-ICR mass spectrometer,and has conducted corresponding application research.The main features of the device mentioned above are as follows:1)The spectral coverage range of the system involves an ultra-wide band of 192 ～ 3700 nm,and can be extended up to 4700 nm,covering the ultraviolet,visible,near-infrared and midinfrared bands.Photodissociation spectra of molecules in different regions can be obtained on the same instrument,providing more information in molecular structures and relative dynamic study.The system can be used for UV photodissociation and structural studies of biomacromolecules with the equipped 193 nm excimer laser.2)For the first time,the confocal method was applied to introduce two tunable lasers into the cell of an FT-ICR mass spectrometer,breaking through the difficulty of introducing multiple lasers into the FT-ICR mass spectrometer due to the structural limitations of the instrument.Taking advantage of this feature,the UVPD spectra of IRMPD fragment ions and the IRMPD spectra of UVPD fragment ions can be obtained.Different combination steps can be further applied to achieve more flexible and diverse ion photoactivation modes,thus to obtain more abundant information of target ions for a better understanding of their structure characteristics and dynamic processes.With the built ultra-wide band photodissociation mass spectrometry-spectroscopy instrument,some typical related studies have been carried out and some important experimental results have been obtained.The results are listed below.1)The UV photodissociation mechanism of protonated tryptamine has been studied systematically.Firstly,the ionic structure of protonated tryptamine in gas phase was determined using IRMPD spectroscopy combining with theoretical calculation.UVPD experiments found that the UV photodissociation products of protonated tryptamine are closely related to the wavelength of the irradiated UV laser.Based on the suggested ionic structure,the main four UV dissociation channels have been studied in detail by the comparison of theoretical calculation and experiments.The Mc Lafferty-type rearrangement reaction induced by ultraviolet photon has been explained for the first time.Deuterated experiments were used to prove the suggested mechanism.2)By taking the advantages of the experimental setup,isomers with different types(substituent position isomers,diastereomers and enantiomers)have been differentiated using the flexible combination of photon activation and other tandem mass spectrometry methods.The results also provide new ideas for the isomer study in the gas phase using mass spectrometry.