| Environmental pollution and food safety issues have threatened the quality of life and health of the people.Currently,in order to analyze the harmful substances in food and environmental sample,the complicated pretreatment,and chromatographic techniques are required prior to mass spectrometry as most sensitive detection tool.However,due to the long detection time,large scale instrumentation and highly technical threshold of these traditional analytical methods,these techniques are not suitable for on-site sample analysis.Ion mobility spectrometry(IMS)is a fast,portable and trace detection technology.IMS is suitable for on-site rapid detection and screening because of its operation under atmospheric pressure,small size,simple operation and rapid response.Nowadays,this technique is widely applied for on-site detection of dangerous substances such as drugs and explosives on airports and customs.In our work,the library of IMS about environment pollutants and illegal additives in food was established,and a series of sample pretreatment methods were developed to couple with IMS for on-site screening real samples in the field of environment and food safety.The contents of this thesis were summarized as follows:(1)In order to realize the integration of on-site enrichment and detection of PAHs,a new method was developed which coupled fabric phase sorptive extraction(FPSE)with IMS for on-site rapid detecting polycyclic aromatic hydrocarbons(PAHs)present in water.The ion mobility spectra of 12 PAHs were obtained in positive ion mode,and reduced mobilities of 12 PAHs were calculated by the internal calibration.The polydimethylsiloxane(PDMS)was coated on the glass fiber cloth through a sol-gel reaction.After extraction of the PAHs in water,the fabric coated PDMS was directly put into the inlet of IMS for thermal desorption.The primary parameters affecting extraction efficiency were investigated and optimized by using phenanthrene(Phe),benzo[a]anthracene(BaA)and benzo[a]pyrene(BaP)as model compounds.Under the optimal conditions,the FPSE-IMS detection limits for model compounds was 5 ng mL-1,8 ng mL-1 and 10 ng mL-1 respectively.The satisfactory recoveries were obtained in the range from 80.5%to 100.5%by testing the spiked real water samples and validated by the standard method(HJ487-2009).Based on the results,the method of FPSE-IMS can be feasibly applied for on-site monitoring the water quality,providing quick warning in the field.(2)Considering the microporous structure and high specific surface area of MOFs material which can directly enhance the adsorption capacity for FPSE,the glass fabric was modified by UiO-66 and coupled with IMS.Glass Fabric@UiO-66-CD-IMS was applied to screen the three adulterants(theophylline,caffeine and emodin)in weight-loss dietary supplements.UiO-66 film was modified in situ,on the surface of activated glass fiber by solvothermal growth,and was characterized by XRD,BET and SEM.The film has a microporous structure with a specific surface area of 802.332 m2 g-1.The peaking regularity and resolution of three adulterants in IMS were studied.According to the intensity of its response,the effects of extraction temperature,extraction time,stirring rate,pH value,ionic strength and elution time on extraction and desorption efficiency were discussed.Under the optimum conditions,the materials prepared in this work have higher extraction efficiency for the three adulterants when compared with the PDMS coating.The methodologies of IMS were studied by using blank matrix of weight-loss dietary supplement.The recoveries were calculated through testing low,middle and high spiked levels samples in the range of 88.0%-118.1%with RSD between 0.7%-16.0%,and the LOD was 10 ng mL-1.This method was validated by UPLC-MS/MS,and the recovery and precision were in a suitable range.Moreover,these values were comparable with other reported methods.Therefore,Glass Fabric@UiO-66-CD-IMS can potentially be applied for the screening and detection of dietary supplements in the field.(3)In order to improve the selectivity of the extraction for target compounds,considering the structure of Sudan dyes(Ⅰ-Ⅳ),nickel-foam@polydopamine(NF@PDA)was prepared through the self-polymerization of dopamine on the nickel-foam surface under weak alkaline conditions and used as SPME material to selectively extract the Sudan dyes.And the Sudan dyes(Ⅰ-Ⅳ)were firstly detected by IMS.Foam metals as adsorbing carrier material which have three-dimensional(3D)cross-linked grid structure can provide high surface area,indicating NF@PDA with high mass adsorption capacity.Under the optimized IMS instrument parameters,four Sudan dyes were detected given that migration times of ions in positive mode were different from each other in IMS.Under the optimal extraction conditions,the detection limits for Sudan dyes were in the range from 0.005 ug g-1 to 0.25 ug g-1.The spiked recoveries were in the range from 81%-91.3%by testing tomato sauce and hot-pot sample and validated by the UPLC-MS/MS(which recoveries in the range of 83.1%-108.2%).Based on the results,the PDA coating has great ability for the extraction of Sudan dyes,mainly due to the catechol structure,electron-deficient quinones and amine groups on its surface.Thus,the developed method has great potential for on-site rapid screening of the Sudan dyes in food quarantine field.(4)In order to realize the high throughput analysis,a reliable and novel coupling of pipette-tip micro-solid phase extraction(PT-μSPE)with corona discharge ionization-ion mobility spectrometry(CD-IMS)was developed for on-site fast detection of benzodiazepines(BZDs)in dietary supplements.The poly(styrene-co-divinylbenzene)(St-co-DVB)monoliths fabricated in pipette-tips through an in-situ polycondensation reaction.The extraction procedure of PT-μSPE for aqueous sample was performed for an appropriate number of aspirating/dispensing cycles by using a manual micropipettor.Then analytes retained in the polymeric monoliths were eluted with elution solvents by repeating the aspirating/dispensing cycles,and the eluates were analyzed by CD-IMS.In order to find the best extraction conditions,several parameters affecting extraction efficiency were investigated.Under the optimal conditions,the LOD of this method which was tested by using spiked samples was in the range of 5-15 ng mL-1.The spiked recovery values in real sample were obtained by PT-μSPE-IMS in the range of 84.2%-112.1%and validated by UPLC-MS/MS.Both of recoveries obtained by this method and by the validation method(UPLC-MS)are in the range of 80%to 120%,which confirms that this method can be used for on-site fast screening of BZDs used as adulterants in the dietary supplements.In addition,the high throughput analysis of this method can be realized by treating sample with a multichannel micropipette. |
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