Development Of Multiresidue Analytical Method For Pesticides In Allium Vegetables

A UPLC-MS/MS method was developed for the simultaneous determination of45pesticides residues in Chinese chives on the basis of establishing the analysis conditions ofUPLC-MS/MS and optimizing the sampe prepatation method. Then, the method wasvalidated on the other three kinds of allium vegetables, which were Welsh onion, onion andgarlic, and some allium vegetables from the Hefei market were tested. The main resultswere summarized as following:1. The MRM parameters for45pesticides were automatically optimized by using theIntelliStart technology of XevoTMTQ MS. With methanol as the B phase of mobile phase,the effects of5kinds of buffer solvent as the A phase of mobile phase on the sensitivity ofevery pesticide were compared. Five kinds of buffer solvent were5mmol/L ammoniumacetate,0.1%formic acid,0.01%formic acid+0.05%ammonia,0.1%formic acid+5mmol/L ammonium acetate and water. Based on formic acid buffer being selected, theeffects of formic acid buffer of different concentrations on the sensitivity of every pesticidewere compared. In order to consider pesticides of the low sensitivity,0.05%formic acidbuffer was selected as the A phase of mobile phase.2. The effects of the water content in sample diluent （methanol-water） on recoveriesof pesticides after filtering membrane were studied. The results showed that when thewater content was higher, the recoveries of some pesticides with later peak time were lower.When the water content was decreased, the recoveries of pesticides with later peak timebecome better, but the peak shape of pesticide with earlier peak time went worse gradually,the peak shape extending forward or backward. Considering both the pesticide recoveryand the peak shape, methanol-water solution containing50%water was selected as samplediluent.3. The effects of homogenate extraction and ultrasonic extraction on the extractionefficiency of pesticides in Chinese chives were compared. The results showed that whenthe sample was extracted by ultrasonic method for5minutes, the number of pesticideswith recoveries between70%and120%was largest, reaching43and95.56%of the totalnumber of pesticides. In addition, at the same time only one sample was extracted byhomogenate method, while several samples can be extracted by ultrasonic method.Ultrasonic method had the advantages of simple operation and high efficiency. Therefore,the ultrasonic method was selected, and the extraction time was5minutes.4. With acetonitrile+toluene （3+1） as elute，the elute volume of eluting pesticidescompletely in the PestiCarb/NH₂SPE column was studied. The results showed that most of45pesticides can be eluted completely from the SPE column by15mL of elute. However, acephate, carbendazim, coumaphos, avermectin and chlorbenzuron can be elutedcompletely from the SPE column by25～35mL of elute, but eluting with20mL of elutecan obtain satisfactory recoveries. From the point of view of environmental protection,economy and high efficiency,21mL of elute was selected. The eluting method was thatusing2mL of elute to wash sample bottle for three times, and loading the washing liquidinto the SPE column, then loading other5mL of elute directly into the SPE column forthree times.5. The limit of detection（LOD）of the method was estimated by referring to U.S.EPA standard. The lowest fortified concentration that had been done actually and metrequirements was regarded as the limit of quantification （LOQ） of the method. LODs andLOQs of the method for45pesticides in Chinese chives ranged from0.1μg/kg to4.7μg/kgand from1μg/kg to10μg/kg respectively. Both LODs and LOQs were not higher thanpesticide maximum residue limits （MRLs） which were regulated in the standard GB2763-2012, meeting the requirements of pesticide residue analysis.6. With the optimized method, the recovery experiment at three spiked concentrationlevels of0.01,0.1,0.2mg/kg was tested for Chinese chives. The recoveries of45pesticidesranged from64.7%to114.4%, and the RSDs were varied from1.1%to18.1%. The resultsshowed that the method can be used for quantitative analysis of45pesticides in Chinesechives.7. The recovery experiment on the other three matrixes of welsh onion, onion andgarlic was tested to evaluate applicability of the method. The percentages of the number ofpesticides which met the recoveries from60%to120%and the RSDs less than30%in thethree matrixes were97.8%,100%and95.6%respectively. The results showed that themethod can be used for fast analysis and confirmation of45pesticides in welsh onion,onion and garlic. For the vast majority of all of the45pesticides, the method can bequantitative accurately.8. Chinese chives, welsh onion, onion and garlic from the Hefei market were tested.Four pesticides （carbendazim, pyrimethanil, acetamiprid and Imidacloprid） weredetected and the concentration ranged from3.0μg/kg to18.6μg/kg. The results showed thatthe method can be used in practice for the pesticide multi-residue analysis of alliumvegetables.