Determination And Sources Analysis Of Mineral Oil Hydrocarbons(MOH) In Edible Oils And Oily Seasonings

Contamination of mineral oil hydrocarbons(MOH)in foodstuff has raised lots of concern recently.In the present paper,solid phase extraction(SPE)coupled with programmable temperature vaporizer(PTV)-based large volume injection-gas chromatography-flame ionization detection(LVI-GC-FID)was used to determine mineral oil saturated hydrocarbons(MOSH)in edible oils and oily seasonings.MOSH contamination were detected in 35 samples and the chromatograms were compared with those of hydraulic fluid,auto engine oil,lubricating oil,etc.to analyze the source of MOSH.The methods were preliminarily explored to eliminate the olefins and to determine mineral oil aromatic hydrocarbons(MOAH)in edible oils and oily seasonings.The results were obtained as follows:(1).The 5 mL SPE column(8 cm×13 mm,coated with aluminum foil)was packed with 3 g 0.3%Ag-activated silica gel as stationary phase and hexane was used as mobile phase to separate MOSH from edible oils and oily seasonings.MOSH was determined by LVI-GC-FID after concentration by nitrogen blowing.The limit of quantification was 1 mg/kg and the linearity range was 1-200 mg/kg(R2=0.999)using paraffin as MOSH standard.The recoveries were 93.22-103.93%and the intra-day and inter-day relative standard deviation were 5.40 and 2.95%,respectively.(2).MOSH in 35 samples(including 16 edible oils,9 spicy oils and 10 hotpot/spicy-pot condiments)were detennined by the established method and all the samples was contaminated with>5 mg/kg MOSH.MOSH in 12 vegetable oils and 4 animal fats were 7.46-107.66 and 5.37-11.46 mg/kg,while MOSH in 9 spicy oils and 10 condiments ranged 12.24-28.13 and 15.35-71.90 mg/kg,respectively.(3).MOSH in food grade lubricating oil and gear oil was centered at n-C31 while MOSH in hydraulic oil,auto engine oil and No.32 machinery oil was centered at n-C28.MOSH in printing oil ranged from n-C12 to C23 and centered at n-C17.Among all 35 samples,ten of them were probably contaminated by hydraulic oil,auto engine oil,No.32 machinery oil or lubricant oil,while fourteen samples were potentially contaminated by lubricating oil or gear oil.Three samples were probably contaminated by printing ink.(4).The separation between MOSH and MOAH was carried on a SPE column loaded with 3g 0.3%Ag-activated silica gel as stationary phase.Mobile phase were 4 mL hexane and 16 mL 5%toluene/20%dichloromethane/75%hexane sequentially.3-Chloroperbenzoic acid(mCPBA)was used for epoxidation to eliminate olefins interference in the determination,but epoxidation would also cause a loss of MOAH.Totally six samples(including camellia oil,rice oil,peanut oil,extra virgin olive oil,spicy oil and hotpot condiment)were tested for MOAH contamination,one of them was under detection limit but four samples were with a ratio of MOAH/MOH lower than 30%.