GC-MS Determination of 16 Phthalates in Plant Oil with Magnetic Graphene Oxide as Adsorbent in Separation and Purification

The 1st step to the determination of 16 phthalates (PAEs) in plant oil by GC-MS was to separate the analytes from oil sample. 0.500 0 g of the sample was taken and extracted ultrasonically with 100 μL of n-hexane and 2 mL of acetonitrile for 5 min. The mixture was centrifuged for 5 min and the supernatant was collected. The lower phase remained was re-extracted with 2 mL of acetonitrile, and the 2nd supernatant obtained was combined with the 1st one. The combined supernatants were evaporated by N₂-blowing at 40℃ to near dryness, and the residue was dissolved with 1 mL of acetonitrile. To this solution, 250 mg of anhydrous MgSO₄, 80 mg of PSA and 50 mg of magnetic graphene oxide were added in succession, and the mixture was extracted ultrasonically for 5 min. Phase separation was attained and the supernatant was collected by external magnetic field and was to be used as sample solution for GC-MS analysis. An aliquot of 1 μL of the sample solution was introduced into the gas chromatograph and the 16 PAEs in it were separated on the chromatographic column of RXI-5si1MS under the condition of programed temperature elevation in the interval from 80℃ to 280℃. EI ionization source and mode of SIM were adopted in MS analysis. Matrix matching was used in preparation of standard curves, and linearity ranges found for the 16 PAEs were same between 0.02-1.00 mg·L^-1, with their detection limits (3S/N) ranged from 0.005-0.008 mg·kg^-1. Using blank plant oil as matrixes, test for recovery was made by standard addition method, giving values of recovery in the range of 82.2%-111%. RSDs (n=6) found for the 16 PAEs were in the range of 1.0%-7.2%. Five samples of plant oil were analyzed by the present method, and 5 PAEs were found in separate samples.