Dissertation > Excellent graduate degree dissertation topics show

Application of Dispersive Liquid-Liquid Microextraction Coupled with Gas Chromatography in the Analysis of Organic Residues

Author: CuiShuMin
Tutor: ZuoJiGen
School: Zhejiang Normal University
Course: Analytical Chemistry
Keywords: Dispersive liquid-liquid microextraction gas chromatography plasticizer residues pesticide residues
CLC: O657.7
Type: Master's thesis
Year: 2013
Downloads: 84
Quote: 0
Read: Download Dissertation

Abstract


Samples pretreatment is time-consuming and easy to bring measurement error. The traditional sample pretreatment methods such as liquid-liquid extraction, solid phase extraction suffer from the disadvantage of tedium and a great deal of toxic organic solvent to be used and so on. In recent years, a lot of research workers have focused on the development of new sample preparation methods, which are less time-consuming, economical, efficient and environmentally friendly. Dispersive liquid-liquid microextraction (DLLME), introduced by Rezaee et al in2006, is a novel liquid-liquid microextraction technique, which is a simple and fast microextraction technique based on homogeneous liquid-liquid microextraction (HLLE) and cloud point extraction (CPE). The method usually need only10microliter of extractant. In the process of extraction, the well dispersion of the extraction solvent (assisted by the disperser solvent) in the aqueous solution will lead to the generation of a significantly large contact area between the extraction solvent and the aqueous phase. The equilibrium is quickly reached and the analyte is enriched in a short time. It also has other advantages such as simplicity of operation, low cost, high enrichment factor and recovery and environment friendly.This work combines dispersive liquid-liquid microextraction with gas chromatography-flame ionization detection (GC-FID), has established a new sample pretreatment method to analyse plasticizer and pesticide residues in environment samples. The main research contents are as follows:(1)A simple and efficient method for the simultaneous extraction and determination of four plasticizer (diethyl phthalate, dibutyl phthalate, butyl benzyl phthalate, dioctyl phthalate) residues in wine samples was developed using dispersive liquid-liquid microextraction (DLLME) combined with gas chromatography-flame ionization detection (GC-FID). The parameters, including type and volume of extractant and dispersant, extraction time and salt amount on the extraction performance were investigated and optimized in detail. Under the optimal conditions:30μL CCl4was used as extraction solvent,0.75mL isopropanol was used as disperser solvent,1%(w/v) NaCl and60s extraction time, good linearity was observed for all analytes in the range of1-200μg L-1with correlation coefficients (r2)>0.9938. The limits of detection (LODs) for the analytes based on signal-to-noise of3were between0.34and0.75μg L-1. The enrichment factors for the four plasticizer residues were ranged from233,473,340and340folds. The precision for these analytes, as indicated by relative standard deviations (RSDs) were less than6.12%(n=5), for both intra-and inter-day analysis. The proposed method was successfully applied for the preconcentration and determination of four plasticizer residues in the two wine samples with mean recoveries in the range of86.5%-106.4%.(2)A simple and efficient method for the simultaneous extraction and determination of six pesticide residues (prometryn, buprofezin, trizophos, λ-cyhalothrin, pyridaben, esfenvalerate) in water samples was developed using ultrasonic-assisted dispersive liquid-liquid microextraction (UA-DLLME) combined with gas chromatography-flame ionization detection (GC-FID). The parameters, including type and volume of extractant and dispersant, extraction time and salt amount on the extraction performance were investigated and optimized in detail. Under the optimal conditions:15μL CCl4was used as extraction solvent,1.00mL acetonitrile was used as disperser solvent,5min extraction time and no salt added, good linearity was observed for all analytes in the range of1～100μg L-1with correlation coefficients (r2)≥0.9990. The limits of detection (LODs) for the analytes based on signal-to-noise of3were between0.09and0.57μg L’1. The precision for these analytes, as indicated by relative standard deviations (RSDs) were less than4.82%(n=5), for both intra-and inter-day analysis. Further, the enrichment factors for the six pesticides were ranged from315to1153fold. The proposed method was successfully applied for the preconcentration and determination of six pesticides in the environmental water samples (river water, tap water, lake water) with mean recoveries in the range of90.5%～107.7%. The proposed method could satisfy the requirements for the determination of different pesticide residues in water samples.(3)A simple and efficient method for the simultaneous extraction and determination of five pesticide residues (buprofezin, trizophos, λ-cyhalothrin, pyridaben, esfenvalerate) in water samples was developed using ultrasound-assisted dispersive liquid-liquid microextraction method based on solidification of floating organic droplet (UA-DLLME-SFO) combined with gas chromatography-flame ionization detection (GC-FID). Under optimal conditions:8μL1-dodecanol was used as extraction solvent (its toxicity was much lower than that of extraction solvent in traditional DLLME),300μL acetonitrile was used as disperser solvent,1%(w/v) NaCl,3min extraction time and5min centrifugation time at4000rpm, good linearity was observed for all analytes in the range of0.20μg L’1-200μg L-1(n=3) with correlation coefficients≥0.9976, enrichment factors were obtained between143and813. Limits of detection (S/N=3) ranged between0.11and0.48μg L-1, depending on the compounds. Relative standard deviations (%) were less than3.49%(n=5) for both intra-and inter-day analysis. The proposed UA-DLLME-SFO method was successfully applied for the determination of pesticides in water samples (river water, tap water, lake water) with mean recoveries that varied from94.10%to109.40%(RSDs<5.01%).

Related Dissertations

  1. Study on Preparation of Biodiesel Catalyzed by Solid Base,TE667
  2. Study on Removal Efficiency of Organic Phosphorus Pesticides Residues by Ultrasonic and Air Bubble Cleaning,S481.8
  3. Analysis on Organophosphorus Pesticide Residues of Vegetables and Control Measures in Lianyungang,S481.8
  4. Present Situation, Problems and Thecountermeasures for the Rapid Determination Technologies of Pesticide Residues in Vegetables in Shanghai,S481.8
  5. Determination of Organophosphorus Pesticides Residues by Fluorescence Method and Its Application,O657.39
  6. Study on the Matrix Solid-Phase Dispersion Applications of Pesticide Residues in Food,TS207.53
  7. Study on the Migration of Esters Additives in Food Plastic Packaging Materials,TS206.4
  8. Variation of Aroma Components in Jiupei of Fen Liquor during Fermentation,TS262.32
  9. Pesticide Residues Status and Impact on Quality in Fruits, Shanxi Province,TS255.7
  10. Prediction of Gastric Cancer Metastasis through Urinarymetabolomic Investigation,R735.2
  11. Studies on Screening Determination of Multiclassification Multipesticide Residues in Vegetables,S481.8
  12. Study on Composition and Combustion Performance of Biodiesel,TE667
  13. Cold -induced ionic liquid dispersive liquid-liquid microextraction Determination of organic matter in water samples,O657.72
  14. Determination of Organic Pollutants in Tap Water by Disperisve Liquid-liquid Microextration-high Performance Liquid Chromatography,O657.72
  15. Identification of Aroma Active Compounds in Essential Oils and Tobacco Leaves Using Gase Chromatography-Mass Spectremetry/Olfactometry (GC-MS/O),TS411
  16. Single herb Citrus aurantium Citrus aurantium Citrus aurantium and medicine - dried tangerine peel , ginger - clove volatile compounds,R284
  17. Study on the Detection and Migration of Bisphenol A (BPA) in Food Cans Inner Coatings,TS206
  18. Study on Separation of Isopropanol-water Azeotrope Using the Coupling Process of Biomass-based Fixed-bed Adsorption and Distillation,TQ223.123
  19. Mycorrhizal residual impact on vegetable phoxim,S481.8
  20. Study on Determination of Thiamethoxam and Clothianidin Pesticides in 14 Kinds of Agricultural Products by UPLC-MS/MS,S48
  21. GC-MS determination of organic contaminants in the sample preparation method,X832

CLC: > Mathematical sciences and chemical > Chemistry > Analytical Chemistry > Instrument analysis ( physics and physical chemistry ) > Chromatographic analysis
© 2012 www.DissertationTopic.Net  Mobile