| Biological volatile organic compounds (VOCs), containing importantbioinformation, are produced by biological metabolism and bacterial populationlocalized on the surface of biological samples. Biological VOCs are trace with the lowmolecule weight and complicated composition, and in most cases in-vivo sampling isneeded for the study of biological VOCs. Development of the suitable samplingmethod has been the bottleneck of the study of biological VOCs. Solid-phasemicroextraction (SPME) as one of the excellent sampling methods possesses the highenrichment factor for sampling biological VOCs and remains the releasing balance ofbiological VOCs. However, the extraction capacity and selectivity of commercialSPME fiber coatings can not totally satisfy the requirement of sampling biologicalVOCs. Thus, it is necessary to develop the novel and efficient SPME fiber coatingsfor sampling biological VOCs. Nanostructure alumina with small size has the strongabsorption to biological VOCs due to the extremely large surface area, especially onedimension nanoarray structure alumina. In this paper, we aimed to prepare the novelnanostructure alumina SPME fiber coatings for the real application for the study ofbiological VOCs coupling with gas chromatography-mass spectrometry (GC-MS)detection and chemometrics strategy interpretation. The main content of the thesiscovers the following three sections.1. The advances on the study of biological VOCs were introduced. Theapplication advances of commercial and novel home-made SPME fiber coatings insampling biological VOCs were summarized. Then, the preparation methods ofSPME fiber coatings and the application of nanostructure materials for the preparationof SPME fiber coating were reviewed in detail. Finally, the necessity and significance,main content and novelty point of this thesis were summarized.2. The nanoarray porous anodic alumina (NPAA) SPME fiber coating wasprepared by a two-step anodization method, and the anodic voltage and time duringpreparation were optimized respectively. The surface morphology of NPAA SPMEfiber coating was characterized by scanning electronic microscopy (SEM) analysis,and the nanoporous array structure was confirmed. The extraction capacity and selectivity of the novel SPME fiber coating were preliminary studied by a mixedstandard biological VOCs model coupled with gas chromatography-mass spectrum(GC-MS) detection. Compared to the commercial PDMS SPME fiber coating, NPAASPME achieved the higher enrichment factors (1.4-4.7folds) for the mixed standardbiological VOCs and showed the higher extraction selectivity for polar biologicalVOCs. Then, an NPAA SPME-GC-MS method was established and successfullyapplied for the qualitative and semi-quantitative analysis of biological VOCs fromBailan flower (Michelia alba DC.), normal and irritated stinkbug (Tessaratomapapillosa), orange peel (Citrus reticulata Blanco) and seasoned orange peel. Suitablechemometrics strategy was used to interpret the VOCs profiles of biological samplesat different physiological status. Finally, the typical trace VOCs of orange peel andseasoned orange peel,1-octanol and nonanal, were quantified.30,12,27,44and38VOCs were identified for Bailan flower, normal and irritated stinkbug, orange peeland seasoned orange peel, respectively. The VOC profile characteristics of normal andirritated stinkbugs were interpreted by principal component analysis (PCA), anddifferent clustering rules were achieved in PCA model. The contents of1-octanol inorange peel and seasoned orange peel were found to be16.1and7.6μg/L, and thecontents of nonanal in orange peel and seasoned orange peel were found to be14.6and0.4μg/L, respectively. The recovery for the determination of trace1-octanol andnonanal is in range of85.4-120.1%with the relative standard deviations (RSDs) of4.8-23.3%. The results suggest that the novel NPAA SPME fiber coating is applicableand reliable for sampling biological VOCs and the consequent study of biologicalVOCs.3. The alumina nanowires (ANW) SPME fiber coating was prepared by atwo-step anodization method, and the concentration of corrosion solution of sodiumhydroxide and corrosion time during preparation were optimized respectively. Thesurface morphology of ANW SPME fiber coating was characterized by scanningelectronic microscopy (SEM) analysis, and the one dimensional nanowire structurewas confirmed. And the extraction capacity and selectivity of the novel ANW SPMEfiber coating were preliminary studied coupled with gas chromatography-massspectrum (GC-MS) detection. Compared to NPAA SPME fiber coating, ANW SPMEpossessed the higher extraction capacity and selectivity for biological VOCs. Then, anANW SPME-GC-MS method was established and successfully applied for thequalitative and semi-quantitative analysis of the VOCs of banana samples at yellow-ripe, full-ripe, over-ripe and non-enzymatic browning storage phases.26,30,30and29VOCs were identified for yellow-ripe, full-ripe, over-ripe andnon-enzymatic browning banana samples respectively by ANW SPME samplingcoupled with GC-MS detection. PCA was used to interpret the VOCs profilecharacteristics of banana samples at different storage phases, apparently differentclustering rules were achieved in PCA model. Then, a common mode analysis wasapplied to distill5typical esters contributing most to the difference ofchromatographic profile characteristics of banana samples at different storage phases.The quantitative results of the above5typical ester VOCs showed the good recoveryin range of107.8-115.4%with RSDs of2.6-6.7%. The results suggest that the novelANW SPME fiber coating is applicable and reliable for the study of banana VOCs atdifferent storage phases. It is hopeful that this research would provide a potentialflavor method and basic data for the alarming and evaluation of banana disease. |
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