Research Of Solid-phase Extraction Based On Mesoporous Alumina And Its Application In Analysis Of Pesticide Residues In Food

The characteristic of pesticides and veterinary drugs residue in food including: thelower content of target analytes in samples, complex matrix and lots of impurities.It isdifficultied for separation and purification, which makes the sample preparationtechniques for analysis of pesticide residues more tedious. Therefore, development ofrapid and efficient sample pretreatment technology becomes one of hot topics. Solidphase extraction is widely used in pretreatment of sample owing to the high enrichmentefficiency, low dosage of organic solvent and easy automation. The choice of adsorbentis the most important influence factors. In past years, nanomaterials are widely usedbecause of their unique structure and property, for example, nanometer materials has aprominent advantage in the sample separation and purification of agriculture andveterinary drug residue. Therefore the nanomaterial combine with biology, immunology,electrochemical and material technology being used in pesticide residue analysis, cangreatly improve the analysis of the detection sensitivity, accuracy and detection effect. Itbecome the forefront of analysis and determination of pesticide resedues.Mesoporousaluminas is a novel inorganic functional material, its unique chemical and physicalproperties such as crystalline structures, textural characteristics and acid–base properties,especially excellent catalytic activity, which resulted in many researches andapplications in various fields.This paper focued on the application potential ofmesoporous alumina as the research object. The main content of the thesis are asfollows.(1) In this paper, we summarized the progress on sample preparation techniques foranalysis of pesticide residues, application of new adsorbents in sample pretreatmenttechnology, synthesis of mesoporous alumina, analysis and determination of pesticideresedues.(2) Mesoporous alumina were obtained with aluminum iso-propoxide, HNO3as pHadjustor, block copolymers F127as template, and we had concentrated on the factorsaffected on the structure, morphology, BET surface areas, pore sizes and volumes of themesoporous alumina, such as different synthesized time and different calcinedtemperatures.(3) Mesoporous alumina was investigated for being used as a new solid phaseextraction adsorbent with abamectin and ivermectin as the target analytes in vegetablesby liquid chromatography-tandem mass spectrometry (LC-MS/MS). The chromatographic separation was conducted on a C18column (100mm×2.1mm,1.7μm)using a gradient mobile phase consisting of methanol (solvent A) and0.2%formic acidin5mmol L-1ammonium acetate (solvent B) buffer at a flow rate of0.3mL min-1. Thelinearity of the calibration curves was excellent and yielded the correlation coefficients(r2=0.9990-0.9999, at a range of0.02-0.50mg L-1). Samples were spiked with knownquantities of the analytes at three different concentration levels (0.05,0.10, and0.20mgL-1) and the recoveries were in the range of87.3%-104.5%with relative standarddeviation (RSD) values ranging between0.53%and5.8%. The limits of detections andlimits of quantization were0.16ng g-1and0.53ng g-1, respectively. These resultsindicated that mesoporous alumina had enormous potential in food security field as anovel solid phase extraction adsorbent material, which with good purification effect,high precision, good reproducibility, good accuracy, and the recovery meet therequirements. The mesoporous alumina solid phase extraction can be used fordetermination of abamectin and ivermectin in vegetables, which has greater practicalsignificance and application value.(4) A gas chromatographic method based on mesoporous alumina solid-phaseextraction was developed for the simultaneous determination of16kinds oforganophosphorous pesticides in vegetables、fruits and tea, including cabbage, lettuce,pumpkin, onion, tomato, turnip, apple, pear and tea. The samples were extracted withethyl acetate, and clean up with mesoporous alumina as solid-phase extraction adsorbent.The separation of target compounds were performed on a film thickness of DB-1701capillary column, and the quantitative analysis of organophosphorous pesticides wascarried out by gas chromatography with flame photometric detector. The results showthat the calibration cueves of16organophosphorous pesticides were linear in the rangeof0.01-2.00mg/L with good correlation coefficierts (γ≥0.997). The recoveries of thepesticides in different samples at three spiked levels ranged from83.2%to103.8%,with relative standard deviations of2.0%-9.9%. The mesoporous alumina solid-phasedispersion synthesied in our experiment shows good effect. This method with highsensitivity, high accuracy and good repeatability, and it can be applied to thedetermination of organophosphorus residue in different matrixs, such as vegetables,fruits, and tea.