Analysis Of Shellfish Toxin And Environmental Hormone In Foods By Pressurized Capillary Electrochromatography

In this thesis, some contaminators in foods were analyzed by pressurizedcapillary electrochromatography, and new methods related to amnesic shellfishpoisoning, phenolic xenoestrogens and organophosphorous pesticides wereestablished. The developed methods were also applied to the analysis of targetcompounds in shellfish tissues, eggs, milk powder, vegetables and fruits.There are four chapters in this thesis, and the main contents are listed asfollows:In chapter1, pressurized capillary electrochromatography (pCEC) performedby electroosmosis flow (EOF) combined with the forward and reverse pressure inthe separation process, is a recently developed micro-column electro-separationtechnique which combines the high efficiency of capillary electrophoresis andhigh selectivity of high performance liquid chromatography.In chapter2, a new method was developed to quantify domoic acid, thechemical responsible for Amnesic Shellfish Poisoning (ASP), by pressurizedcapillary electrochromatography. The effect of different experimental conditionson the separation of domoic acid and matrix solutes, such as the content ofacetonitrile in mobile phase, pH and concentration of buffer, supplementarypressure and applied voltage, were investigated. Under the optimal conditions, thepCEC method separated domoic acid from shellfish matrices within6min. Byusing supplementary pressure, bubble formation in the capillary column wascompletely suppressed. The method was repeatable, sufficient accurate andsensitive for rapid screening of domoic acid in shell seafood. In chapter3, pressurized capillary electrochromatography with end-columnamperometric detection using carbon paste electrode has been developed for theseparation and determination of five phenolic xenoestrogens in chicken eggs andmilk powder samples. Efficient separation of five analytes was performed bypCEC using a mobile phase consisting of60%v/v ACN and40%v/v Tris buffer(5mmol L-1, pH8.0),+6kV of applied voltage and7.0MPa of supplementarypressure. Detection limits of50,5,2,10, and20ng mL-1for pentachlorophenol,bisphenol-A,2,4-dichlorophenol,4-tert-octylphenol, and4-nonylphenol,respectively, were achieved using carbon paste electrode as working electrode and+0.8V as detection potential. After matrix solid phase dispersion extractionprocedure, mean recoveries ranged from79.2%to102.6%at differentconcentrations of phenolic xenoestrogens for spiked egg and milk powder sampleswere obtained.In chapter4, by adding3,4-Dihydroxybenzylamine hydrobromide (DHBA)in mobile phase, typical organophosphorous pesticides, which belong toenvironmental hormone and have no electroactivity, were separated anddetermined by pressurized capillary electrochromatography with indirectamperometric detection method. The kinds of additives with electroactivity werecompared. The effect of concentration of DHBA and working potential to thebackground current of mobile phase and negative peaks height were studied. Theconcentration of DHBA was selected as0.1mmol L-1, and the working potentialof amperometric detection was selected as0.9V (vs. Ag/AgCl). The optimalanalysis conditions for six organophosphorous pesticides were as follows: mobilephase:50%v/v ACN,50%v/v MES buffer (10mM, pH5.5),0.1mmol L-1DHBA, applied voltage:+10kV, supplymentary pressure:7.0MPa, pump flowrate:0.05mL min-1, electrode potential:+0.9V. The six organophosphorouspesticides, namely, dimethoate, methyl parathion, ethyl parathion, chlorpyrifos,chlorpyrifos-methyl, trichlorfon, were baseline separated within15min, and thelimits of detection were2.0,2.5,0.5,0.5,0.2,2.5g mL-1respectively. After solid phase extraction procedure, recoveries of vegetable samples were ranged from78.9%to87.2%, and that of fruits samples were ranged from81.4%to98.6%.The accuracy of the proposed method was good.