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Application of Dispersive Liquid Liquid Microextraction to Treatment of Environmental Water and Biological Samples

Author: WangYing
Tutor: YuAiMin
School: Jilin University
Course: Analytical Chemistry
Keywords: Room temperature ionic liquid Ultrasonic assisted ionic liquid microextraction Microwave-assisted dispersive liquid-liquid microextraction Homogeneous ionic liquid microextraction Triazine and phenylurea herbicides Quinolones Sulfas
CLC: X832
Type: PhD thesis
Year: 2011
Downloads: 99
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Abstract


In the determination of environmental pollutants, sample preparation is a privotal process. Conventional sample preparation methods, such as liquid-liquid extraction and solid phase extraction, are tim-consuming, tedious, laborious and large amount of toxic organic solvent is required. Therefore, solvent-free extraction for sample preparation and pretreatment has become one of the most important research areas in modern analytical chemistry and attracted much attention recently.Dispersive liquid liquid microextraction (DLLME), which is a new mode of liquid phase microextraction. was proposed recently. In this method, the appropriate mixture extraction solvent and dispersant was injected into an aqueous sample rapidly by syringe. The extraction solvent was dispersed into the aqueous sample as very fine droplets, so the analytes were easily transferred into the extraction solvent. When extraction equilibrium was obtained, phase separation was performed by centrifugation, and the enriched analytes in the sediment phase were determined by chromatographic methods. The advantages of the DLLME are simplicity of operation, rapidity, low cost, high enrichment factors, low detection limit.Among the extraction solvents studied presently, room temperature ionic liquids (RTIL) are promising green solvents. The unique chemical and physical properties of RTIL such as nonvolatility. good thermal stability, broad liquid range, superior solubility and tunable properties, and their application in areas of synthesis, catalysis, separation, electrochemistry, make the RTIL can replaced volatile chemical solvents in many areas.In this thesis, a simple, rapid, and efficient method, based on ionic liquid dispersive liquid-liquid microextraction (DLLME) followed by high performance liquid chromatography (HPLC), has been developed for extraction and determination of triazine herbicides in environmental water samples and biological samples.The ultrasonic-liquid assisted ionic liquid microextraction coupled with high-performance liquid chromatographic detection, has been developed for determination of triazine and phenylurea herbicides. The key parameters, such as the volume of extract solvent, extraction temperature and time, salt concentration in sample solution and pH values of sample solution, were examined and optimized. The recoveries of propzine, trietazine, chlortoluron. linuron from twelve environmental samples at fortification levels (10μg L-1 and 40μg L-1) are 96.0-120.3%(RSD≤10.1%),83.3-102.6%(RSD≤7.7%),82.3-103.8% (RSD≤8.8%),98.8-118.3%(RSD≤9.4%), respectively. The limits of detection for the method for chlortoluron. linuron, propzine and trietazine are 0.50,0.36,1.18, 1.41μg L-1, respectively. The results are satisfactory.Microwave-assisted dispersive liquid-liquid microextraction (MA-DLLME) of herbicides was described. A modified household microwave oven was employed. RTILs can rapidly and effectively absorb the microwave energy and the solubility of RTILs in water increases with the increase of temperature. When the RTILs were used as extract solvent and added into the water samples, the mixture of the extract solvent and water sample was cloudy after a few minutes. Variables influencing the MA-DLLME were evaluated. 1-Hexy 1-3-methylimidazolium hexafluorophosphate ([C6Mim][PF6]) was chosen as extract solvent.3% NaCl (m/v) and 200μL of [C6Mim][PF6] were added into water sample. The sample was cooled down to room temperature by ice water and centrifuged at 8000 rpm. The recoveries of propazine, prebane, chlortoluron. monolinuron. linuron are 62.8-75.5%(RSD≤8.2%), 101.4-116.7%(RSD≤9.1%),82.2-91.0%(RSD≤4.5%),79.8-89.3% (RSD≤6.4%),100.7-120.5%(RSD≤5.6%), respectively. The detection limits of the method are 0.79,0.64,0.56,0.75,1.44μg L-1, respectively. Compared with liquid liquid extraction (LLE), the proposed method requires less volume of sample solution (20 mL) and extraction solvent (200μL). The recoveries for the five analytes obtained by the two methods are almost consistent. So, the proposed method appears to be a useful tool for extraction of herbicides.The determination of triazine and phenylurea herbicides in honey samples by DLLME coupled with high-performance liquid chromatographic detection was described.2.0 g of honey was weighed, added into a 25 mL of centrifugal tube, and diluted to 20 mL with pure water.175μL of RTIL and 50μL of 10% Triton X 114 were injected in the sample solution. After 10 min, the mixture was centrifuged for 5 min at 10000 rpm. The recoveries of prometon, propazine, prebane, chloroturon, linuron were 82.8-105.1%(RSD≤10.2%),62.7-76.8%(RSD≤16.5%),60.1-105.9% (RSD≤12.7%) 82.3-96.9%(RSD≤12.1%),70.9-133.0%(RSD≤13.2%) and detection limits of are 5.84,8.55,5.31,6.92 and 8.59μg kg-1, respectively. The correlation between the recovery and concentration of analytes was analyzed by F test and the results showed that the recovery should not be concentration-dependent.A simple and fast method, homogeneous ionic liquid microextraction (HILME), was developed. Some experimental parameters, such as amount of [C6Mim]BF4, pH value of sample solution, salt concentration in sample solution, extraction time and time of centrifugation were examined. The recoveries from 82.5% to 119.8% were obtained for seven analytes at fortification levels (3μg L-1 and 20μg L-1) with relative standard deviations (R.S.D.)≤8.2%. Fleroxacin and Sulfaquinoxaline were extracted from water samples by using the proposed method. The recoveries from 76.1% to 117.9% were obtained for two analytes with relative standard deviations (R.S.D.)≤9.0%. Compared with DLLME. the proposed method was environment friendly and dispersant solvent was not required.

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