Study On The Application Of Chromatography To Food Analysis

Food is a basic foundation for the existence,generation and health of mankind to rely on.Safe food should be nutritious,not contaminative and shouldn't contain harmful substances that may injure the human health.The harmful substances in food include its own components,contamination outside and the substances formed during storage.The problem of food safety is the main concern for the government,the society and the consumers.To detect the contamination in food is the most effective measure for food safety control.So it is undoubtedly necessary to develop an effective, accurate and fast chromatographic system for the detection of pesticide residues, veterinary remains and the additives in food.The main contents of this thesis are listed below:1.The application of various sample pretreatment techniques to chromatographic analysis and food safety control,including liquid-liquid extraction(LLE),solid-phase extraction(SPE),solid-phase microextraction(SPME),supercritical fluid chromatography(SFC)and gel permeation chromatography(GPC)is reviewed.The application of chromatographic technology in food additive,pesticide residues and veterinary remains analysis is also presented.The QSRR model also reveals that the gas chromatographic RTs are associated with physicochemical property of pesticides and toxicants.QSRR models for the prediction of retention time of pesticides compounds using the heuristic method(HM) and support vector machine(SVM)based on descriptors calculated from molecular structure alone have been developed.2.A simple and rapid method for the determination of ten antioxidants:Proply gallate(PG),n-Octyl gallate(OG),2,4,5-Trihydroxybutyrophonone(THBP), Tert-butylhydroquinone(TBHQ),Butylated hydroxyanisole(BHA),Batylated hydroxytoluene(BHT),Dodecyl gallate(DG),Nordihydroguaiaretic acid(NDGA), 2,6-Di-tert-butyl-4-hydroxy-methylphenol(HMBP)and Isoamyl gallate(IAG)in oils and fats was studied.Ultrasonic extraction was adopted for sample treatment and the extraction solutions were then analyzed directly by ultra performance liquid chromatography-mass spectrometry(UPLC/MS).The extraction solvents and time were selected and the precision,recovery and linear range were investigated.The developed method could effectively extract,separate and determinate the 10 antioxidants in oils and fats.The recoveries(n=6)were 92.56%～102.5%,the relative standard deviations(n=6)were 0.68%～5.12%,and the detection limits were 0.002～0.01mg/L.3.Using sulfuric acid as medium,sodium cyclamate in fruit cans were transformed into N,N-dichlorocyclohexylamine by the effective chloine in sodium hypochlorite.After extraction by n-hexane,an efficient gas chromatography method was developed for the determination of sodium cyclamate in various fruit cans.In which quantitation and confirmation are achieved using GC/ECD and GC/MSD. External calibration was used and calibration curve was linear from 5mg/kg to 200mg/kg with correlation coefficient r=0.9992.The recoveries were between 96.2% and 102.0%with RSD from 0.26%to 2.47%and the detection limit of 2.5mg/kg. Established a method for determination of lactose in squid by HPLC to control the quality.4.Using headspace-solid phase microextraction(HS-SPME)and GC-MS,47 aromatic components in brandy were separated and identified,among which 32 compounds were confirmed,including esters,alcohols,aldehydes,phenols,and organic acids.The results shows that HS-SPME is a useful technique in the analysis of aromatic components in brandy,and makes it possible to quantitatively evaluate its grade.5.An automated solid phase extraction instrument is used to treat with the agri-product,and GC/MS or LC/FLD is used to detect the pesticide residues and veterinary remain.The compounds detected mainly include the organochlorines in dehydrated vegetables,31 kinds of pesticide residues in fruits and vegetables or in animal tissues,9 sulfonamides and 4 quinolones.The method presented here can detect the pesticide residues and veterinary remain in large quantities of samples automatically,which makes it to be a fast,practical and advanced technique in food safety control.6.Quantitative structure-retention relationship(QSRR)studies was reported for predicting the retention times(RTs)of 110 pesticides and toxicants were detected by gas chromatography(GC)with mass selective detector(MSD).Chemical descriptors were calculated from the molecular structure of pesticides and toxicants and the QSRR models of RTs with descriptors were built using the heuristic method(HM)and support vector machine(SVM),respectively.The obtained linear model of HM had a correlation coefficient R~2=0.913,F=116.70 with an root mean square error(RMS) error of 0.0387 for the training set,while R~2=0.907,F=195.49,and RMS=0.0408 for the test set.The nonlinear model by SVM gave better results:for the training set R~2= 0.966,F=2420.5,RMS=0.0231 and for the test set R~2=0.944;F=339.7; RMS=0.0313.The prediction results from nonlinear model are in agreement with the experimental values well.The QSRR model also reveals that the gas chromatographic RTs are associated with physicochemical property of pesticides and toxicants.QSRR models for the prediction of retention time of pesticides compounds using the heuristic method and support vector machine based on descriptors calculated from molecular structure alone have been developed.Satisfactory results were obtained with the proposed method.The proposed linear model could identify and provide some insight into what structural features are related to retention time of these compounds.