| In modern society, more and more people are concerned about food safety.Meanwhile, the food problems caused by pesticide and veterinary residues becomecommon in recent years. For instance,“poison cowpea and clenbuterol affairs”happened in2010and2006, respectively. Therefore, to establish an effective andenvironmental-friendly method to extract and inspect the residues in plant and animalfood become the research hotspot. Nowadays，the extraction reagents used to extracttoxic residues in plant and animal foods mainly include methanol, acetonitrile, acetone,all of which are harmful to our health and environment. Under the circumstance,subcritical water extraction was introduced in the study to extract the toxic residues infoods. Tea and pork were chosen as the main matrix and extraction efficiency wasdetermined to establish an efficient and green pretreatment method.As one of the crops with long history in China, teas are also important andtraditional agricultural exports. Entering the21thcentury, since European and Americancountries carried out more serious MRLs for pesticides residues, the export volume oftea and the economic benefits obtained were declined. European Union and Japanenacted the standard in2010and2006, in which the MRLs of438and273pesticides intea were set respectively. And EU specified712kinds of pesticides which couldn’t bedetermined in imported agricultural products. The sort of pesticides related to tearegulated in national standards in China was9,13and7respectively, and the MRLswere also broaden. For example, the MRLs of cypermethrin in China is20mg/kg whilein EU and Japan are0.5mg/kg, which limits our tea exportation. In this way, thedemand of determining the pesticide residues in tea becomes higher.A gas chromatography-tandem mass spectrometry (GC-MS/MS) method withsubcritical water extraction was developed for the determination of21organochlorineand pyrethroid pesticides in tea. Under the extraction pressure of5MPa, the targetcompounds were extracted with subcritical water at the temperature of150℃for15min, then transferred into acetone-n-hexane （1：1, v/v）, then cleaned-up by anENVI-Carb solid phase extraction（SPE）column. The GC separation was performed ona DB-5capillary column. The pesticides were determined in MRM mode and quantifiedby matrix-matched internal standard method. The calibration curves showed good linearity in the range of5.0-320.0μg/L with the correlation coefficients greater than0.99. The limits of quantification （S/N>10）were50ng/g, and the limits of detection（S/N>3） were10ng/g. The recoveries of pesticides in the tea at three spiked levels of50,100and200ng/g were ranged from70.18%to119.98%with the relative standarddeviations（RSDs）of5.02%-11.76%. The sensitivity, accuracy and precision of themethod meet the technical standard of the pesticide determination. The method can beapplied to the determination of organochlorine and pyrethroid pesticides in tea.β-agonists belong to ethylamine compounds, among which clenbuterol belongs toaniline-type while salbutamol and ractopamine belong to phenol-type. β-agonists areapplied into livestock industry because they can promote animal growth, reduce bodyfat deposits and increase lean meat. But eating too many animal issues containingβ-agonists will cause poisoning, malignant tumor, and even death. In2002, theseveterinaries drugs were listed in “Veterinary drugs and other compounds banned inanimal food list” by ministry of agriculture. In July2012, the MRLs of ractopamine inpork was10μg/kg by Codex Alimentarius Commission（CAC） while USA, Japan andWHO were50,10,40μg/kg respectively and in EU, it was still zero. Besides,clenbuterol and salbutamol couldn’t be detected. As a kind of efficient broad-spectrumantibiotics, chloramphenicol was used to cure infectious disease for animals. While itcould be harmful to our health such as causing aplastic anemia when accumulated in ourbody through food chain. chloramphenicol was listed as banned veterinary drug by USAand EU, and the MRLs were1μg/kg while in MOA Announcement No.193, the MRLswas1.5μg/kg.A liquid chromatography-tandem mass spectrometry（LC-MS/MS）method withsubcritical water extraction was developed for the determination of β-agonists andchloramphenicol in pork. Enzymatic hydrolysis was used during the preparation of porkfirstly，then the target compounds were extracted with subcritical water and cleaned upby C18. The LC separation was performed on Agilent XDB-C18column（4.6mm×50mm，1.8μm）. The veterinary drugs were determined by MS/MS in MRM mode andquantified by matrix-matched internal standard method. The calibration curves showedgood linearity in the range of1.0~32.0ng/mL for Salbutamol and Ractopamine withlimits of quantitation（S/N>10）0.5ng/g and limits of detection（S/N>3）0.25ng/g,0.2~6.4ng/mL for Clenbuterol and chloramphenicol with limits of quantitation（S/N>10）0.1ng/g and limits of detection（S/N>3）0.05ng/g, and the correlation coefficients were greater than0.99. The recoveries of veterinary drugs in pork at threeadded levels were ranged from79.15%to113.02%with the relative standard deviations（RSDs）of3.15%~11.95%. The sensitivity, accuracy and precision of the method meetthe technical standard of veterinary drugs determination, which can be applied to thedetermination of β-agonists and chloramphenicol in pork. |
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