Detection Of Pesticide Residues In Honey Based On ND-EESI-MS And Identification Of Syrup Adulteration By MPT-MS

Honey is of medicinal and edible value,rich in nutrients and bioactive substances.Due to environmental pollution and the need for disease prevention and treatment during beekeeping,there may be residual risks of chemical contaminants such as antibiotics,pesticides,and heavy metals in honey.In addition,adulterated and shoddy problems exsit in honey.Residues of chemical contaminants and adulteration in honey have seriously affected the quality and safety of honey,and hindered the export of honey in China.At present,the methods for the detection of antibiotics,pesticide residues and adulteration in honey mainly include liquid chromatography(LC),gas chromatography(GC),liquid chromatography-mass spectrometry(LC-MS),gas chromatography-mass spectrometry(GC-MS)and stable carbon isotope ratio analysis method(SCIRA),these methods generally require pre-treatment,take a long time,require large amounts of organic solvents,is not conducive to the rapid detection of antibiotics,pesticide residues in honey,but also is not conductive to the rapid identification of honey adulteration.For this reason,this study established a rapid,green,neutral desorption-electrospray ionization mass spectrometry(ND-EESI-MS)method without sample pretreatment to directly detect tetracycline(TC)and five pesticide residues in honey.Meanwhile,a method for the rapid identification of honey and syrup by microwave plasma torch mass spectrometry(MPT-MS)without sample pretreatment was developed.The main research contents and results are as follows:1.Qualitative analysis of TC in honey by lab-made ND-EESI and analysis of TC fragmentation pathways.The experimental conditions of extractant,desorption agent,electrospray voltage,capillary temperature and extractant flow rate are optimized with the signal intensity of TC's MS~2 fragment m/z 427,and the TC in honey was the quantified under the optimized conditions.The standard curve of TC determination in honey was obtained,as well as the limit of detection(LOD),recovery rate and precision.The established method was applied to detection of commercial honey samples and compared with high performance liquid chromatrography(HPLC).The results show that the best experimental conditions for ND-EESI-MS detection of TC residues in honey are extractant:ethanol/water of 20%acetic acid,desorption agent:methanol/water(9:1,v:v),electrospray voltage:3.5 kV,capillary temperature:200?,extractant flow rate:4?L/min.The spiked honey has good linearity in the range of20-1000 ng/m L(R~2>0.997),LOD was 1.08 ng/m L,which was less than the maximum residue limit(MRL)50 ng/g in honey;and the recoveries at the spiked concentrations of 50 ng/mL,500 ng/mL,1000 ng/mL were 94.26%,98.38%,103.00%,respectively;the precisions were 3.28%,1.39%,1.12%,respectively;The ND-EESI-MS used to detect the 8 market honey samples,and showed that 2 honey samples contained trace amounts of TC,while HPLC did not detect TC in all honey samples.2.In order to achieve simultaneous detection of multiple residues in honey,an optimized ND-EESI-MS method was used for detection of 5 pesticides(fenthion,metolcarb,dichlorvos,isoprocarb and chlorpyrifos-methyl)in honey.The result showed that the LOD were 1.16-4.18 ng/g,the recovery and RSD at three different spiked levels(50 ng/m L,500 ng/m L and 1000 ng/m L)were 87.00-114.98%,0.97-6.22,respectively.The method has good repeatability and reproducibility in detecting the residues of fenthion,metolcarb,dichlorvos,isoprocarb and chlorpyrifos-methyl in honey.The matrix effect values of 5 pesticides in honey are-35.71-10.55%.For 18 honey samples,metolcarb,isoprocarb and dichlorvos were not detected in all samples,and chlorpyrifos-methyl was detected in rape honey,clover honey and wildflower honey samples with the contents between 1.80 and 4.24 ng/g,less than the maximum residual limit(MRL 10 ng/g).Fenthion was detected in almost all honey samples,except clover honey,with the content of 4.55-8.62 ng/g,beyond the MRL(10 ng/g)in honey.3.MPT-MS was used for the identification of honey and syrups.Based on the optimization of experimental conditions such as microwave power,support gas flow rate and carrier gas flow rate,the mass spectrometry information of honey and syrup were obtained,and the main ion peaks were analyzed by tandem mass spectrometry.Combining cluster analytical(CA),principal component analysis(PCA),partial least squares discriminant analysis(PLS-DA),discriminant analysis(DA)and other chemometrics methods to distinguish between honey and syrup.The results are as follows:The optimized MPT-MS experimental conditions were:microwave power 80W,support gas flow rate 600 mL/min,and carrier gas flow rate 650 mL/min.The main ion peaks are m/z 198,m/z 180,m/z 163 and m/z 145,which are fragment ions of monosaccharide hydrate,monosaccharide and monosaccharide.MPT-MS combined with chemometrics can quickly distinguish between honey and syrup.PCA shows that PC1,PC2,and PC3 have a total contribution rate of 91.2%;CA shows that when the critical value is 7,honey and syrup can be distinguished effectively except for clover honey and inulin syrup;PLS-DA shows that honey and syrup can effectively distinguish;DA shows that the discriminating accuracy of honey and syrup is 100%.The ND-EESI-MS established in this paper requires no sample preparation,low reagent consumption,high analysis efficiency,high precision,and environmental friendliness.The LOD value is lower than the specified MRL value and can meet the detection requirements.It can provide reference for direct,rapid and green environmental testing of antibiotics and pesticide residues in honey and other agricultural products.MPT-MS does not require sample pretreatment,has high detection efficiency,low cost,and high identification accuracy.It can be used for the identification of honey and main adulterated syrup,and can also provide reference for the detection of adulteration of other foods.