摘要：A method for the determination of phthalic anhydride (PA) in poly (vinyl chloride) (PVC) products by reversed-phase high performance liquid chromatography (HPLC) is described. By the reaction of PA with ethanol, PA is converted to monoethyl phthalate (MoEP), which is further methylated to methyl ethyl phthalate (MEP) with diazomethane. PA could be successfully determined by quantitating MEP. The method is as follows : one gram of chopped PVC sample and 10 mg of Ca, Zn stearate are dissolved in 10 ml of dehydrated tetrahydrofuran. Ten milliliter of ethanol is added to the solution, and the solution is refluxed for 20 min (PA→MoEP). PVC polymer is precipitated by the addition of methanol, and removed by filtration. After shaking the filtrate with cation-exchange resin, MoEP is methylated with diazomethane (MoEP→MEP). The reaction mixture is loaded on a silica gel column, and washed with 50 ml of diethyl ether-hexane (5 : 95) mixture, and eluted with 50 ml of diethyl ether-hexane (10 : 90) mixture. The eluate is evaporated to dryness, and the residue is redissolved in 1 ml of methanol. Five microliter of this solution is injected to HPLC apparatus. HPLC conditions : column, Nucleosil 5 C8 (250 mm×4.6 mm i. d.); mobile phase, acetonitrile-water (60 : 40); flow rate, 1.0ml/min ; detector, ultraviolet detector ; detection wavelength, 254 nm. Calibration curve based on the peak height of MEP was found to be linear in a wide range of 2-1000 μg of PA. However, the amounts of PA found in PVC products were only less than 2.6 μg/g.
