Studies On Direct Sample Introduction On-line Derivatization And Multistage Tandem Mass Spectrometry

Direct sample introduction(DSI)is a novel sample injection technique in gas chromatography(GC).The development of DSI and its combination with the application of on-line derivatization and large-volume sample injection minimize purification procedure and improve sensitivity.The method which uses direct sample introduction together with other sample pretreatment technique can expand its application field.1,9-diphenyl-9H-fluorene is a new organic compound,whose derivatives exist plenty of isomers.The structure of 1,9-diphenyl-9H-fluorene derivatives which have multiple benzene ring are complex.In this paper,direct sample introduction on-line derivatization by ion pair for determining free salicylic acid in aspirin effervescent tablets and benzoic acid in foods were established by gas chromatography-ion trap mass spectrometry.At the same time,this work presented a modified method to analyze methyl-,chloro-,bromo-and trifluoromethyl-substituted 1,9-diphenyl-9H-fluorene and their isomers by ion trap mass spectrometry.A brief description was given as follows:1.The method using direct sample introduction on-line derivatization for determining free salicylic acid in aspirin effervescent tablets was established by sonication-assisted extraction coupled with gas chromatography-mass spectrometry.The ion pair coordination compound was formed with ion pair reagent tetrabutylammonium hydrogen sulfate(TBAHS)and salicylic acid,which could derivative to be salicylic acid butyl ester in the condition of high temperature and made qualitative analysis for salicylic acid butyl ester by gas chromatography-mass spectrometry.Then it made quantitative analysis with external standard method.The calibration curves of the analyte revealed a good linear relationship over the ranges of 1.0?30.0?g/mL(r=0.9978).The limit of detection(LOD)and limit of quantitation(LOQ)of the developed method were 0.09?g/mL and 0.28?g/mL,respectively.It can be concluded that the direct sample introduction on-line derivatization method is an efficient,rapid,simple,environmentally friendly,and cheap technique for the determination of free salicylic acid in aspirin effervescent tablets.2.The method using large-volume on-line derivatization for determining benzoic acid in foods was established by sonication-assisted extraction coupled with gas chromatography-tandem mass spectrometry.Benzoic acid in samples was extracted by acetonitrile solution,and then centrifugated.The samples were stirred with tetrabutylammonium hydrogen sulfate(TBAHS)as derivatization reagent.The method used gas chromatography with ChromatoProbe for on-line derivatization to improve sensitivity.Analysis was performed on a DB-5MS capillary column supplemented with gas chromatography-ion trap tandem mass spectrometry.The calibration curves of the analyte revealed a good linear relationship over the ranges of 0.50?10.0?g/mL(r=0.9976).The limit of detection(LOD)and limit of quantitation(LOQ)of the developed method were 12.8ng/mL and 42.7ng/mL,respectively.This method has the advantages of convenient operation,no need of purification,high sensitivity,excellent accuracy and good reproducibility and is suitable for the determination of benzoic acid in foods.3.This work presented a modified method to analyze methyl-,chloro-,bromo-and trifluoromethyl-substituted 1,9-diphenyl-9H-fluorene derivatives and their isomers by ion trap mass spectrometry with electron impact ionization(EI).Since MS spectra of 1,9-diphenyl-9H-fluorene derivatives with these four groups and their isomers are similar,it is difficult to distinguish them from its isomers.Multistage tandem mass spectrometry analysis involves selecting molecular ions obtained in MS spectra as precursor ions in the MS/MS process,and the fragment[C25H17]+(m/z 317)obtained in MS/MS spectra as a precursor ion in MS3 processes.Collision-induced dissociation(CID)experiments at different activation energies were done to elucidate possible fragmentation pathways.Proposed fragmentation pathways including m/z 317 and structures of the product ions are acquired simultaneously.At a higher CID voltage,the isomers of C25H17-CF3 can be distinguished in MS/MS,while the isomers of C25H17-CH3,C25H17-C1 and C25H17-Br can be distinguished in MS3.The proposed GC-MSn method is a powerful tool to provide large amounts of the necessary structural information to characterize methyl-,chloro-,bromo-and trifluoromethyl-substituted 1,9-diphenyl-9H-fluorene derivatives and its isomers.