Modification And Characterization Of Magnetic Nanoparticles And Its Application Of Solid Phase Extraction Of Biogenic Amines In Fish

Meat and Fish have important nutritional value because they are rich in protein,fatty acids,vitamins and so on.However,proteins of these foods will decompose during processing and storage,following microorganisms will produce biogenic amines(BAs)by releasing amino acid decarboxylase.The freshness and spoilage of these foods are often judged by the content of BAs as a quality control criterion.Nevertheless,it is necessary to enrich and purify by proper pretreatment technology based on the fact that the content of BAs in fish is low and the sample matrix is complex.At present,solid phase extraction(SPE)is much widely used,although the selectivity and adsorption properties of traditional adsorbents for BAs are not ideal enough.For this purpose,the development of green,efficient and simple novel SPE adsorbents has become the research hotspot in recent years.Magnetic nanoparticles(MNPs)have attracted the attention of many scholars due to their unique magnetic responsiveness,biocompatibility and convenient operation.The magnetic solid phase extraction(MSPE)technology developed based on this has also been considered as a new pretreatment technology with brilliant development prospects.In this thesis,kinds of MNPs rich in carboxyl functional groups were prepared by chemical synthesis,their adsorption properties on BAs were studied.MNPs with admirable adsorption properties were selected,and the adsorption and desorption conditions were studied.Finally,it was applied to the detection of BAs in fish.The specific contents and results were as follows:1.The method for the determination of 9 BAs at 254 nm was established by DNS-Cl pre-column derivatization combined with reversed-phase HPLC.Derivatization conditions were optimized as follows:p H=8,DNS-Cl concentration was 5.0 mg/m L,the ether was chosen as extractant with twice extraction.In the methanol-acetonitrile-water ternary mobile phase system,BAs were successfully separated and detected by gradient elution.The resolutions and the peak match were all greater than 1.5 and 995,respectively.The linear relationship ranged from 0.05000-20.00?g/m L is good(R²?0.9990).The LOD and LOQ were in the range of 1.334 to 4.823 ng/m L and 4.446 to16.07 ng/m L,respectively.The sensitivity of the method was high.Finally,it was successfully applied to the determination of BAs in fish.Among them,the total amount of biogenic amines detected in the Sillage sihama(Yangjiang)and Trachinotus ovatus(Zhanjiang)were the highest,which showed that the quality of these samples was worthy of attention.2.The Fe₃O₄ MNPs with a particle size of about 20 nm was prepared by ultrasonic assisted coprecipitation method.Optimization of the synthesis conditions based on FT-IR results were as follows:the mass ratio of the amount of substance of Fe³⁺/Fe²⁺was 0.5:1,the volume of ammonia was 80.0 m L.Besides,the 11 kinds of carboxyl functionalized Fe₃O₄@RCOOH MNPs were prepared by in situ functionalization synthesis.The structure characterizations were carried out by FT-IR?TG?DSC?laser particle size analysis and FESEM.Meanwhile,the differences in the synthesis mechanism of Fe₃O₄@RCOOH MNPs prepared from different carboxylates in terms of thermal stability,particle size,and characteristic functional group absorption peaks were preliminarily investigated.3.The adsorption performance of 11 kinds of Fe₃O₄@RCOOH MNPs were studied,and Fe₃O₄@Ph(OH)COOH modified by salicylic acid was selected as the magnetic adsorbent.Further optimized adsorption conditions were 500 mg of the adsorbent amount,p H was 7,reaction temperature was60?.The desorption was carried out by in situ derivation with DNS-Cl concentration of 10.0 mg/m L and derivative reaction time of 45 min.The adsorption mechanism showed that the adsorption process was more consistent with the pseudo-second-order kinetic model(R²?0.9970),which was both related to physical and chemical adsorption.The particle internal diffusion model showed that the process was accompanied by external film migration and intraparticle diffusion.The Langmuir isothermal model(R²?0.9971)indicated that this was the monolayer synergistic adsorption of homogeneous adsorption sites.4.Based on the Fe₃O₄@Ph(OH)COOH MNPs modified by salicylic acid and HPLC detection method,the determination of BAs in fish samples has been established.The matrix standard working curve in the range of 0.1000-20.00?g/m L demonstrated a good linear correlation(R²?0.9943)and high detection sensitivity(LODs?0.2895?g/kg and LOQs?0.9652?g/kg).The results of the spiked recovery rate showed that the method was accurate(70.41%-125.3%)and had good repeatability(RSD 2.4%-8.5%).Besides,the RSD of intra-day and inter-day precision were between 2.5%-8.7%and 3.7%-7.8%.This method was applied to the detection of BAs in 10 fish samples.As a result,spermine,tyramine,putrescine and cadaverine were the four BAs detected with higher contents.All the 10 batches of samples met the limited requirements,but the total amount of Trachinotus ovatus(Zhanjiang)was the highest and the largest BAI was obtained,indicating that the quality of the sample was worth paying attention to.Secondly,by comparing the changes in the accumulation of BAs in Thunnus obesus under different storage conditions,it laid the foundation for the food control.