植物油中过氧化值检测方案

KoMApplication Note NTIB-99309 Fat and Oil Peroxide value of Oleic acidRedox titration byAutomatic Potentiometric TitratorTest Method for Analysis of BasicSFatty MaterialtandardISO 3960 1.Abstract The oleic acid is widely distributed in plant and animal fats. Measurement ofperoxide value (POV) of oleic acid is demonstrated in this application according to thebelow quoted test method. The test sample is first dissolved in mixture of chloroformand acetic acid(2：3). By flowing nitrogen gas through the sample to dispel residualoxygen， add potassium iodide， and then titrate free iodine with 0.01mol/L sodiumthiosulfate. The endpoint is determined by the maximum inflexion point on titration curve.POV is calculated from titration volume of sodium thiosulfate. I2+2Na2S2O3i→ Na2S4O6+2NaI 2.Reference 1)Test Method for Analysis of Basic Fatty Material by Japanese Oil ChemistrySociety； Reference material 2.4-1996 Peroxide value (Chloroform Method) 2))ISO 3960 ： 2007 Animal and vegetable fats and oils -Determination of peroxidevalue 3. Cautions in measurement 1))Do not use water containing carbon dioxide in preparing saturated potassiumiodide solution. 2)To confirm saturation，add excessive potassium iodide to the saturatedpotassium iodide solution， and leave crystal in the solution. 3Prepare fresh saturated potassium iodide each time. If the sample does not change color to yellow due to free iodine when saturatedpotassiumiodide is added， add more saturated potassium s perfo1iiodide except whenblank test inirmed or if peroxide value is very small in number. 5)Before potassium iodide is added， flow nitrogen gas through the sample to dispelresidual oxygen. 6If potential change around EP is small， adjust Gain of Control parameter. Http：//www.shxf17.com 4.Post-measurement care Rinse the electrode with pure water， and keep it dipped in water to avoid drying up. 5. Test equipment Main unit ：Automatic potentiometric titrator (Standard preamplifier： STD-) Electrode Option Combination Pt. electrode 6. Reagent Reagent 0.01mol/L Sodium thiosulfate (f=1.006) Solvent Mixture of chloroform and acetic acid(2：3) Additive ： Saturated potassium iodide Inactive gas ：Nitrogen gas 7.Measurement procedure -measurement- 1))Deliver approx. 5g sample into a conical flask with stopper. 2))Add 30mL solvent and gently shake to dissolve the sample completely. 3))Gently replace the air inside flask with nitrogen to remove remaining oxygen. 4)By further flowing nitrogen gas， add 0.5mL saturated potassium iodide， andimmediately seal the flask and gently shake it for one minute. 5))Leave the flask at room temperature (15 to 20°C) in a dark room. 6)Add 30mL pure water， and seal it and stir. 7)Titrate with 0.01mol/L sodium thiosulfate to measure peroxide value.※Likewise， obtain blank level in advance by a blank test. 8. Formula Peroxide value (meq/kg)=(EP1- BL1)×TF×R/SIZE EP1 ：Titration volume (mL) BL1 ： Blank level (0.00mL) TF ： Factor of reagent ( 1.006) R ： CConstant(10) SIZE ： Sample size (g) Http：//www. shxf17.com 9. Example of measurement -Ambient condition· Room temperature ：22.5℃ Humidity： 147% Weather： Cloudy -Titration parameter-·Titration curve- Model ： AT-510Method No. ： 11Titr.mode ：Auto Intermit Titr.form1·： EP Stop Titration parameter] Form ： FEP Stop APB No. ：： 1Unit No. .： 1Detector No. ：Unit ： rmVMax.Volume ：10.0mLWait Time ：0s Direction ： Auto [Control parameterl End Point No. ： 1End sense ： AutoEnd Point Area： OffSeparation ：(OffOver Titr.Vol. ：0mLGain ：]10Datasamp.Pot.： 4.0mVData samp.Vol.： 0.1mLStability ： 0.5mV/sDelay Time ：： 1sLimit Time ：： Os [Result parameter] Calc. Type ：Sample Conc.1 ： Set CO1=(EP1-BL1)*TF*R/SIZE Unit ： meq/kgEP No. ：1 Temp.Comp.： Off R ： 10 Factor ：1.006Conc ：(0.01 Blank1 ：(0.00 ***Result *** Sample No. ： 41-01 Date： 1999/07/06 11：49Sample ID ： Method No. ： 11 Titr. Time：： 00：10：33 Size ：5.0794g Conc-1 ：2.6095meq/kg End point-1Volume ：1.3176mLPotential： 213.3mV100 [mU] 3000.000 2.000 [mL] (The above printout data were obtained from titration by AT 510 unit) 《Titration parameter> Form： of titration / APB No. the burette used in titration / Unit No.： APB Unit File numberDetector No.： the detector used in titration / Max Volume： of titration / Wait Time： before titration startsDirection： of titration 《Control parameter>End Point No. number of EPs detected / End sense： direction of EP / End Point Area： detection areaSeparation： of potential/ Over Titr.Vol.over-titration volume /Gain： sensitivity of detection signalData samp.Pot.： potential changes of sampling signal / Data samp.Vol.： titration volume of sampling signalStability： of titration/ Delay Time： before stability check / Limit Time： for stability check《Result parameter>Calc.Type： of formula / Conc.1 formula 1 / Unit of result EP No. for calculation / Temp.Comp. temperature compensation of titration liquid / R： constant Factor： of reagent / Blank1： blank level 1 -Measurement results-一 Peroxide value Sample(g) Titration ( mL) POV (meq/kg ) 2 3 Mean SDRSD 5.0043 5.0095 2.6267 meq/kg0.0186 meq/kg0.7095% 1.3176 1.3053 1.3179 2.60952.6241 2.6465 *The above results were obtained by 3 tests of the same sample. *Red underline shows the data from page 3/4. 10. Summary The oleic acid reduces bad cholesterol(LDL) of monounsaturated fatty acids but doesnot reduce good cholesterol(HDL). Recently， such advantage attracts publicattention， and cooking oil like canola oil or olive oil which contains oleic acid is onthe market. Unsaturated fatty acid like oleic acid and linoleic acid are liable to beoxidized with ambient oxygen. Its quality can be controlled by measuring POV.The measurement results this time shows favorable repeatability with 0.7% relativestandard deviation. Precise and reliable measurement is assured by the automatedpotentiometry. POV of oleic acid can be perfectly measured by any of the following titration systemsmanufactured by Kyoto Electronics (KEM). 【AT-610】 【AT-510】 【AT-500N-1】 AwardedProductt ofSupremeTechnology from Kyoto City · Compact and cost performancemodel ·Low cost and high performance · Easy view with back light LCD● GLP/GMP conformed model 。 Easy key entry by touch panel oflarge color LCD (8-inch wide) · PC card expands data memory forconvenience and versatility. · Simultaneous titration in parallel · Both potentiometric and KarlFischer moisture titration(coulometric"volumetric)can beperformed at a time. KEM KYOTO ELECTRONICSMANUFACTURINGCO.，LTD. Overseas Division： Yamawaki Bldg 9F，4-8-21 Kudan-minami，Chiyoda-ku， Tokyo 102-0074 JAPAN Phone：+81-3-3239-7333， Fax： +81-3-3237-0537 Head Office： 56-2Ninodan-cho，Shinden，Kisshoin，Minami-ku， Kyoto 601-8317 JAPAN Phone：+81-75-691-4122，Fax： +81-75-691-9961 URL： http：//www.kyoto-kem.com 上海旭风科学仪器有限公司 上海市闸北区荣路 el： Fax： 周峰 zhou-feng com