Application Of Chromatography-mass Spectrometry In Food And Drug Analysis

Part one Development of a method for rapid determination of morpholine in juices and drugs by gas chromatography-mass spectrometryObjective: A new method for rapid determination of morpholine residues in fruit juice and drugs was developed by derivatization and gas chromatography-mass spectrometry.Method: Morpholine can react with sodium nitrite under acidic condition to produce stable and volatile N-nitrosomorpholine derivative.In this experiment,various factors affecting the derivatization and extraction process were optimized,including concentration and volume of hydrochloric acid,quantity of saturated sodium nitrite,derivatization temperature and time,extraction reagents and time.The derivative was extracted with dichloromethane and determined by gas chromatography-mass spectrometry.Results: The linearity range of morpholine was 25-500 ?g/L with good correlation.The limits of detection(LOD)was 7.3 ?g/L,and the limits of quantification(LOQ)was 24.4 ?g/L.The spiked recovery rate ranged from 94.3% to 109.0%,the intraday repeatability was 2.0%-4.4%,and the interday reproducibility was 3.3%-7.0% in apple juices and ibuprofen samples.The developed method has good accuracy and precision.Conclusion: This quantitative method for morpholine is simple,sensitive,rapid,and low cost and can successfully be applied to analyze the residual morpholine in apple juices and ibuprofen drug samples.Part two Studies on the metabolism in vitro and degradation in simulated aquatic environment of vancomycin by UHPLC-Triple-TOF-MS/MSObjective: The study aimed to identify vancomycin metabolism in vitro and its natural degradation in aquatic environment,as well as speculated the chemical structures of the related metabolites or degradation products.Method: Accordingly,we established four incubation systems,using a constant temperature oscillator at 37 °C for 10 days for vancomycin in activated rat liver microsomes(experimental system),inactivated rat liver microsomes(control system),phosphate buffered saline(PBS system)and pure water(pure water system),as well as an additional system of activated rat liver microsomes without vancomycin(blank system),and daily sampling.The metabolism in vitro and degradation in simulated aquatic environment of vancomycin were studied by high resolution and high sensitivity ultra-high performance liquid chromatography with Triple time-of-fight mass spectrometry(UHPLC-Triple-TOF-MS/MS)in positive ion mode.The MetabolitePilot 2.0 software was used for screening the probable degradation products.Results: Vancomycin was degraded with a certain degradation rule in the four incubation systems.A similar degradation rate of vancomycin in activated rat liver microsomes system and inactivated rat liver microsomes system confirms that the effect of cytochrome P450 enzymes of activated rat liver microsomes on vancomycin is weak.In the four incubation systems,four probable degradation products were identified and their production rules were summarized.Then,their chemical structures were speculated and the degradation pathways of vancomycin were established.Conclusion: The results of this study provide a foundation for evaluation of the effects of vancomycin and its degradation products on environmental safety and human health in the future.Part three A combination approach of untargeted and pseudotargeted metabolomics to distinguish live from dead pork meat by liquid chromatography-mass spectrometryObjective: In order to ensure the quality and safety of pork meat,a combination approach of untargeted and pseudotargeted metabolomics was used to determine reliable and stable differential markers which can distinguish between pork meat from live pigs conventionally slaughtered and pork meat from dead pigs slaughtered immediately after death.Method: Firstly,an ultra-high performance liquid chromatography with Triple time-of-fight mass spectrometry(UHPLC-Triple-TOF-MS)-based untargeted metabolomics method was used to detect all metabolites.The acquired raw data was processed with the XCMSplus software to extract and statistically analyze all the features.Subsequently,the information of the precursor ion and MS/MS fragments of the differential metabolites,selected according to the screening rules,was used to construct ion pairs and establish a pseudotargeted metabolomics method.In addition,the UHPLC with quadrupole linear-ion-trap mass spectrometry(UHPLC-QTRAP-MS)-based pseudotargeted metabolomics method was used to accurately quantify the differential metabolites.Finally,the differential markers were determined according to the results of statistical analyses performed with the MarkerView software to remove some false-positive metabolites.Results: In this study,24 differential metabolites were screened by the UHPLC-Triple-TOF-MS-based untargeted metabolomics method,and 14 differential markers were determined by the UHPLC-QTRAP-MS-based pseudotargeted metabolomics method.Among the differential markers possibly identified using the Metlin database and references were carnosine,L-carnitine,L-histidine,N-acetylhistidine,acetylcholine,L-acetylcarnitine and two phosphatidylcholines.The beta-alanine metabolism and histidine metabolism pathways were probably the mainly differential pathways between live and dead pork meat groups.Conclusion: In this study,the combination approach of untargeted and pseudotargeted metabolomics can identify reliable and stable differential markers,which can be used to distinguish live from dead pork meat.