Study On Some Sample Preparation Technologies In Seperation And Determination Of Drug Residues

For the past few years, drug residues in environment and food had evokedpeople’s attention because of drug abuse in agricultural production andagricultural products. In this thesis, we selected some pesticides and estrogen astarget and focused on these two problems. One was sample preparation indetermination of drug residues and the other was molecular imprinting membrane inapplication in seperation and determination of estrogen. The aim purpose of thethesis was to develop sample pretreatment with high enrichment fact,miniaturization, environment friendly, easily operation, less time, cheap andanti-interference, and molecular recognition technologies with selectivilyrecognition capability to target molecular, adapting complicated matrix, andapplication in seperation and determination of some estrogen.In general, this thesis is divided into three parts, including six chapters. Thefirst part is also the first chapter. In this chapter, we reviewed the recentdevelopment of sample preparation technology and the molecular imprintingmembrane, and we also proposed the future prospects of sample preparationtechnology. At the end of this chapter, we briefly introduced the research goals aswell as the contents and achievements of this thesis.The second part of the thesis includes three chapters, which is chapter2,chapter3and chapter4. This part mainly focuses on the sample preparation(hollow fiber-mediated liquid-phase microextraction, single-drop liquid-phasemicroextraction and dispersive liquid-phase microextraction). In chapter2, weestablished three-phase hollow fiber-mediated liquid-phase microextractionfollowed by HPLC for the determination of three synthetic estrogens, namelydiethylstilbestrol, dienestrol and hexestrol. Extraction conditions including organicsolvent, volume ratio between donor solution and acceptor phase, extraction time,stirring rate, donor phase and acceptor phase were optimized. The targetcompounds were extracted from a10mL aqueous sample at pH1.5(donorsolution) through a45mm in length hollow polypropylene fiber that wasimmersed in1-octanol in advance, and then the hollow fiber filled with10μL0.5mol/L sodium hydroxide solution (acceptor phase). After a40min extraction, the acceptor phase was directly injected into a HPLC system for detection. Under theoptimized extraction conditions, a large enrichment factor (more than300fold)was achieved for the three estrogens. The determination limit at an S/N of3ranged from0.25to0.5ng/mL for the estrogens. The recovery ratio was more than89%in the determination of these estrogens in wastewater.In chapter3, A new approach for the extraction of nine kinds oforganochlorine pesticides (OCPs) from vegetable samples coupling single-dropmicroextraction with gas chromatography–mass spectrometry was presented.Experimental parameters, such as organic solvent, exposure time, agitation andorganic drop volume were controlled and optimized. An effective extraction wasachieved by suspending a1.00μL mixed drop of acetone and p-xylene (2:8, v/v) tothe tip of a micro-syringe immersed in a2mL donor aqueous solution and stirredat400rpm. The approach was applied to the determination of OCPs in vegetablesamples with a linearity range of0.05to20ng/mL for α-, β-, γ-,δ-hexachlorobenzene (BHC) and dicofol,0.5to20ng/mL for dieldrin and2,2-bis(4-chlorophenyl)-1,1-dichloroethane (DDD) or0.5to50ng/mL for2,2-bis(4-chlorophenyl)-1,1-dichloroethylene (DDE) and2-(2-chlorophenyl)-2(4-chlorophenyl)-1,1,1-trichloroethane (p,p’-DDT). Correspondingly, thedetermination limit at an S/N of3ranged from0.05ng/mL for α-, β-, γ-, δ-BHC to0.2ng/mL for dicofol, dieldrin or p,p’-DDT. The relative recoveries were from63.3%to100.0%, with repeatability ranging from8.74%to18.9%(relativestandard deviation, RSD). The single-drop microextraction was proved to be a fastand simple approach for the pre-concentration of organochlorine pesticides invegetable samples.In chapter4, a novel method was investigated for the determination ofestrogens in wastewater by ultrasonic assisted ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate,([C4MIM][PF6])dispersive liquid-phasemicroextraction coupled with high performance liquid chromatography. Someconditions that might affect the extraction efficiency such as volume of solution,pH value of solution, ultrasonic time, hierarchical standing time and centrifugingtime, were optimized. The results indicated that the optimal conditions were7mLsolution at pH2.0for6min of ultrasonication,30min of hierarchical standing and10min of centrifugation. Under the above mentioned conditions, the extractionefficiency of ionic liquid based ultrasonic microextraction for the three estrogens were about100. Their linear ranges and detection limits were1.0～100.0ng/mLand0.55～1.0ng/mL respectively. The proposed method was applied to determinethe three estrogens in wastewater. The recoveries of the three estrogens spiked inwastewater were in the range of89.0%～96.6%.The third part of this thesis mainly focuses on the synthesis and application ofmolecular imprinting membrane. This part includes chapter5and chapter6. Inchapter5, we synthesized a novel molecularly imprinted polymer (MIP)-coatedpolypropylene hollow fiber tube (HFT) of diethylstilbestrol (DES) as a templatemolecule, α-methacrylic acid (MAA) as a functional monomer, and ethyleneglycol dimethacrylate (EGDMA) as a crosslinking agent. The characteristics andapplications of the MIP-coated hollow fiber tube (MIP-HFT) were investigated. Inorder to compare the characteristics with the non-imprinted polymer-immergedhollow fiber tube (NIP-HFT), the selectivity of the MIP-HFT was investigatedwith dienestrol and hexestrol as the structural analogues of diethylstilbestroltemplate, and phenol and phenolphthalein were taken as reference compounds.The MIP-HFT was employed in HPLC application for milk samples. The detectionlimits were found to be in the range of2.5to3.33ng/mL for DES, dienestrol andhexestrol, and their recoveries were83.7to90.6%, respectively, in spiked milksamples. The experimental results revealed that the MIP-HFT provides a goodcarrier for the selective adsorption of DES and its analogs in chemical structure,and can be used for the pre-concentration of these compounds in complicatedsamples.In chapter6, we prepared the17β-Estradiol molecularly imprintedcomposite membrane through UV initiation by using porous cellulose acetatemembrane as support. The selective binding properties and separation capacity ofthe membranes were investigated．The results showed that the17β-Estradiolmolecularly imprinted composite membrane had high binding capacity for17β-Estradiol，the binding amount Q for17β-Estradiol was10.2μmol／g andseparation factor was4.7for17β-Estradiol／17α-ethinylestradiol．Permeationexperiment results showed that the molecularly imprinted composite membranecould separate17β-Estradiol from17α-ethinylestradiol. The bonding forcebetween17α-ethinylestradiol and the membrane was weaker than the template.