Establishment And Application Of HPLC-FLD And GC-MS-MS Methods Of Polvcyclic Aromatic Hvdrocarbons(PAHs) In Oils And Oil Materials

This article, by establishing the PAHs detection technology of HPLC-FLD andGC-MS-MS, provides essential data for safety monitor on edible vegetable oil. Based onsuch methods, the origin, distribution and migration of PAHs in vegetable oil areexplored, and the production of PAHs under high temperature environment as well as themethod to remove PAHs are studied, all with an aim to guarantee the quality and safetyof edible oil.Based on the PAHs detection method of edible oil of molecular imprintingsolid-phase extraction, combining the HPLC-FLD detection technology, this paperestablishes a rapid detection method (i.e. the HPLC-FLD method) for PAHs in edible oils.The linear range of HPLC-FLD determination method ranges from1-100μg/L with thecorrelation coefficient greater than0.999. The limit of quantitation and limit of detectionranges from0.14-2.25μg/kg and0.04-0.76μg/kg respectively. Except naphthalin andacenaphthene, which have relatively low recovery rate due to their strong fugacity,recovery rate of all other PAHs measured range from70.2-110.0%. A PAHs contentsurvey was conducted on165oil samples covering soybean oil, vegetable oil, peanut oil,olive oil, corn oil, etc., and the result shows that91.5%of them are contaminated byPAHs in varying degrees, and59.3%in heavy degree. PAHs content in3%of the oilsamples exceeded China’s edible oil standard, among them safflower oil and blend oilhave exceeded20%and30%, which is the highest exceed amount;28.5%of the oilsamples exceeded EU’s Benzo[a]pyrene limitation, exceeding rate of blend oil, peanutoil and flax seed oil are66.7%、53.3%and40.0%;26.1%exceeded EU’s generallimitation against total content of4PAHs, among them blend oil, peanut oil and sesameoil have relatively high exceeding rate, which are53.3%、53.3%and37.5%respectively.To avoid high PAHs background caused by oil extraction from solution with largevolume, detection method on extracting PAHs through Acetonitrile and Tetrahydrofuranof oil materials has been established. The recovery rate measured range from between81.7-96.5%and the limit of detection ranges from0.07-0.61μg/kg. The migration rate ofPAHs of oil plants and solvent in edible oil is measured respectively from tworespects--vegetable oil material and extraction solvent. The migration rates of each PAHsof n-hexane in soybean ranges from55.5-117.3%, while the migration rate of PAHs of soybean in soybean ranges from28.9-116.9%. This detection also probes into theinfluence of each process in simulated refine system to the PAHs contents. Theinfluences such as hydrated degumming and decolorization have little effect to PAHs,while the activated carbon adsorption and deodorization play a significant role inremoving it. It also studies the migration rule of PAHs in the course of actual refinement.Diverse PAHs are existed in the crude oil of soybean, tea seed and coconut. After therefining of grease, PAHs will decline step by step and the degumming process play asignificant role in removing PAHs, while the deodorization process is of significanteffect to the removal of PAHs.The absorption mechanism of activated carbon to Benzo [a] pyrene has been alsostudied. Through N,N-dimethyl formamide solvent system, it indicates that theadsorption of Benzo[a]pyrene in activated carbon could be divided into two phases: arapid adsorption phase and following with a slow adsorption phase. Within0.5min ofadsorption, the adsorption is conducted in a rapid manner but slow manner in the laterphase. After30mins’s of adsorption, it achieves a balance. The adsorption isotherm ofactivated carbon to Benzo[a]pyrene is more conform to the Langmuir equationisothermal adsorption model, with adsorption kinetics conforming to the second leveladsorption kinetic model. The adsorption of compound adsorbent to PAHs indecolorization has also been studied. A satisfying decoloration effect and desorptioneffect of Benzo[a]pyrene will be embodied if conducted under110℃, adding1.5%activated clay and0.3%activated carbon and decolor it for30min.For complex oil solution that beyond HPLC-fluorescence method’s detectioncapability, a MISPE-GC/MS/MS method has been established on PAHs of edible oils.The liner range of GC/MS/MS determination method ranges from2-100μg/L, withcorrelation coefficient greater than0.99. The limit of quantitation and limit of detectionrange from0.60-1.93μg/kg and0.18-0.58μg/kg. Except naphthalin, acenaphthene andfluorene, which have relatively low recovery rate due to their strong fugacity, recoveryrate of all other PAHs measured range from71.4-101.0%.The production regularity ofPAHs has also been studied under different temperature and different time. The originallight PAHs will volatile or resolve after heated under lower temperature (200℃), andregenerates under the environment of400℃and450℃. With the extension of heatingtime, the PAHs amounts will also increase continuously.