Determination Of Polycyclic Aromatic Hydrocarbons In Frying Oils And Correlation Analysis With Oil Deterioration

Polycyclic aromatic hydrocarbons(PAHs)is a common environmental pollutant,most of them are carcinogenic,teratogenic,and mutagenicity.The limited standard of PAHs in fat and oil was established at home and abroad.Among them,the four European Union limited PAHs are abbreviated as PAH4,the sixteen kinds of PAHs that are preferentially controlled by the U.S.Environmental Protection Agency(EPA)and the 15+1 species in the European Union are abbreviated as PAH8.PAH10 includes ten kinds of PAHs containing 4~6 aromatic rings in the list of priority pollutants of EPA.The frying system is very complicated and the detection of trace PAHs in frying oil is difficult.Based on the optimization of the detection method,the contents of PAH4,PAH8 and PAH10 in frying oil are determined and the possibility of PAHs in frying oil is explored.The main research contents are as follows.(1)Optimized pretreatment conditions and detection instrument conditions for 10 kind of PAHs determination methods in frying oil.Compared the purification effects of C18 solid phase extraction(SPE)column,Florisil SPE column,Silicone SPE column is combined with liquid-liquid extraction and Molecularly imprinted polymer(MIP)SPE column.Compared the detection performance of samples by HPLC-FLD,GC-MS,and UPLC-MS/MS.And optimized the purification and detection conditions.The results showed that the oil residue from samples was less and the detection pattern was clear after purifying oil sample used the MIP-SPE column.UPLC-MS/MS detection was more accurate and the detection limit is lower.The linear range of the optimized 10 kinds of PAHs was 0.25~50 ng/m L,and the regression correlation coefficient was more than 0.99.The limit of detection and the limit of quantitation for PAHs ranged between 0.10 and 0.40 mg/kg and between 0.33 and 1.33 mg/kg,respectively.The methods' recoveries and precision for PAHs were 81.40%~101.14% and 2.05%~11.69%,respectively.The results met the test requirements for oil samples.(2)The distribution of PAH4,PAH8 and PAH10 in 45 frying oil samples after frying peanuts were determined,which used soybean oil and two blended oil.The results showed that there was no significant difference of PAHs content in the three raw oils(P>0.05).Among the frying oil samples,the contents of PAH4 were concentrated in the range of 4.2~5.7 ?g/kg,which accounted for 59.52% of the total samples.The contents of PAH8 were concentrated in the range of 5.6~6.8 ?g/kg,which accounted for 47.62% of the total samples.The contents of PAH10 were concentrated in the range of 13.5~17.5 ?g/kg,which accounted for 64.29% of the total samples.The contents of PAHs in three kinds of fried oil showed that the distribution of pyrene,benzo[a]anthracene,benzo[b]fluoranthrene and benzo[a]pyrene in the soybean oil was significantly higher than that those of the blends.The PAHs contents in the two blends have no significant differences.(3)For frying oils,changes in the total polar components(TPC),the polar component compositions,PAH4,and PAH10 and the correlations between them were investigated.Stepwise regression model was used to explore possible causes of PAHs in frying oil.The results showed that the relationships between PAH4 and TPC and between PAH10 and TPC were 0.725 and 0.776,respectively.The results showed that the relationships between PAH4 and Oxidized triacylglycerol(ox-TG)and between PAH10 and ox-TG were 0.908 and 0.852,respectively.The results showed that the relationships between PAH4 and Oxidized triacylglycerol polymer(TGP)and between PAH10 and TGP were 0.915 and 0.880,respectively.In contrast,the PAHs contents had no significant correlations with hydrolysis products,and the relationships between PAH4 and AV(r=0.423)and between PAH10 and AV(r=0.597)were lower,which suggested that the formation of PAHs in frying oil may be related to oxidation and polymerization during high-temperature frying.A stepwise regression model was established to exclude redundant variables.The regression equation was y=3.198x+10.650,r=0.893.The results showed that the content of PAHs was positively correlated to that of triacylglycerol oligomers(TGO).