Study On Analysis Methods For Determining Harmful Residues In Food By HPLC-MS/MS

Food is necessary for existence and development of mancind. In recent years, withthe unprecedented development of food industry, food safety scandals emergeendlessly. Peoples are more and more concerned about the food safety problem.Research on key technology on food analysis and safety detection is necessary.Because there are many types of food samples, the chemical composition of the foodis complex, and contents of harmful substances are very low, the separation anddetermination of the substances food are very difficult. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) technologies have a wide application range,high sensitivity, strong anti-interference ability and the advantages for determiningtrace substances. So they have been more and more important in food analysis.Considering the difficulties of the food analysis, two methods for food safety analysisbased on LC-MS/MS are developed:Part I：The high performance liquid chromatography-trandem mass spectrometrywas applied to the determination of the quaternary ammonium residues, includingdodecyltrimethyl ammonium bromide, dodecyldimethylbenzylammonium chloride,tetradecyldimethylbenzylammonium chloride, hexadecyldimethylbenzylammoniumchloride and didectyldimethylammonium chloride, in pork, beerliver, apple, spinach,rice and white suger. The analytes were extracted using methanol-water mixture asextraction solvent, and further purified with Oasis WCX cartridge. The separation ofquaternary ammonium compounds was performed on a CAPCELL PAK CR1:4column using acetonitrile-50mmol/L ammonium format aqueous solution containing0.1%formic acid as mobile phase in a gradient elution mode. The mass spectrometricdetection was operated by using electrospray ion source in the multiple reactionmonitoring mode. The results showed that the linear range for5quaternary ammonium compounds was5.00～500.00μg/L, and the correlation coefficients werehigher than0.995. The limit of quantification for the analytes was10.00μg/kg. Sixkind of real samples were analyzed and the recoveries of the analytes at three spikedlevels were between73.8%and103.6%with the relative standard deviations of0.8%～8.3%. The present method is simple, reliable and accurate and can be appliedto the determination of quaternary ammonium residues in foodstuffs.Part II：The high performance liquid chromatography-trandem mass spectrometrywas applied to the determination of the metabolites of four nitrofuran drugs includingfiirazolidone, furaltadone, nitrofiirantoin and nitrofurazone, in egg white powder,soybean milk powder, milk powder, egg and yoghourt. The method involves the acidhydrolysis of the protein-bound drug metabolites in a60℃water bath, derivatizationof the resulting metabolites with2-nitrobenzaldehyde (2-NPA) during16hoursincubation in a37℃water bath, and further purified with Oasis HLB cartridge. Theseparation of metabolites was performed on a ZORBAX SB C18（150mm×2.1mm,3.5μm） column using acetonitrile–0.1%formic acidaqueous solution as mobilephase in a gradient elution mode. The mass spectrometric detection was operated byusing electrospray ion source in the multiple reaction monitoring mode. The internaland external standard methods were applied. Under the optimum conditions, the linearrange for4metabolites was1.00～10.00μg/L and the correlation coefficients were0.9971～0.9999. The limit of quantification for the analytes was1.00μg/kg. At thethree spiked levels of1.00,2.00and10.00μg/kg, recoveries were in62.0%～113.7%,the relative standard deviations were between0.8%～11%. The present method wassuccessfully applied to the determination of four nitrofuran drug metabolites in eggsnd dairy product samples, and a satisfactory results were obtained.