Iodine value of Oil and Fat - KEM Kyoto [PDF]

Iodine value of Oil and Fat

Petroleum

Redox titration by Automatic Potentiometric Titrator JIS ASTM ISO

Standard

K 0070 D 1959 3961

1.Abstract Test method for measurement of iodine value of fats and oils stipulated in the below quoted standards is generally practiced by Wijs Method using monobasic iodine, however, Hanus Method is demonstrated here using iodine bromide. Firstly, sample fat is dissolved in carbon tetrachloride, and Hanus reagent is added and left in a dark room for reaction. Then, potassium iodide is added for titration with 0.1mol/L sodium thiosulfate. The endpoint is the maximum inflexion point on titration curve. The iodine value of fatty sample is calculated from titration volume of sodium thiosulfate. 4I2

+

Na2S2O3

＋ 5H2O

→

2NaI

+

２H2SO4

＋ ６HI

2.Reference 1) JIS K 0070-1992 Test Method for Acid value, Saponification number, Ester number, Iodine number, Hydroxyl value of Chemical products and Unsaponifiable matter 2) ASTM D 1959-97 Standard Test Method for Iodine Value of Drying Oils and Fatty Acids 3) ISO 3961:1996 Animal and vegetable fats and oils – Determination of iodine value

3.Cautions in measurement 1) Reagent and additives must be handled in a well ventilated room or in a draft. 2) Blank test is required as necessary. 3) Use a 300mL conical flask with ground-in stopper to avoid sublimation of iodine when the sample and Hanus solution react.

TIB-99424 Ver.01 1/4

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 titration system (preamplifier: STD) Electrode: Option Combination platinum electrode

6.Reagent Reagent ： Additives ：

0.1mol/L sodium thiosulfate （ｆ＝1.006） Pure water, Carbon tetrachloride, Hanus solution, 15% Potassium iodide

7.Measurement procedure ―Measurement― 1) Deliver 0.1g sample to a 300ｍL conical flask with ground-in stopper. Add 20.0mL carbon tetrachloride and seal. Dissolve in an ultrasonic washing machine. 2) Add 25.0mL Hanus solution, and seal. Shake for one minute. 3) Keep it sealed and leave in a dark room (about 20°C) for 30 minutes. 4) Add 10.0mL of 15% potassium iodide and 100ｍL water, and seal. Shake for 30 seconds. 5) Titrate with 0.1mol/L sodium thiosulfate to obtain iodine value. Likewise, perform blank test to obtain blank level.

8.Formula Iodine value ( cｇ / g ) = ( BL1 － EP1 ) × TF × C1 ×K1 / SIZE EP1 ： Titration volume ( mL ) BL1 ： Blank level ( 47.074mL ) TF ： Factor of titrant ( 1.006 ) C1 ： Concentration conversion coefficient ( 1.269 ) (Atomic mass of iodine: 126.9/100) K1 ： Unit conversion coefficient ( 1 ) SIZE ： Sample size (ｇ)

TIB-99424 Ver.01 2/4

9.Example of measurement －Ambient condition－ Room temperature：23 ℃

Humidity ：

23 ％

-Titration parameterModel : AT-510 Method No. : 10 Titr.mode : Auto Intermit Titr.form : EP Stop

Weather ：

Rainy

-Titration curve-

[Result parameter] [Titration parameter] Form APB No. Unit No. Detector No. Unit Max.Volume Wait Time Direction

: : : : : : : :

EP Stop 1 1 1 mV 40.0mL 0s Auto

[Control parameter] End Point No. End sense End Point Area Separation Over Titr.Vol. Gain Data samp.Pot. Data samp.Vol. Stability Delay Time Limit Time

: : : : : : : : : : :

1 Auto Off Off 0mL 1 4.0mV 0.5mL 0.5mV/s 1s 30s

Calc. Type : Sample Conc.1 : Set CO1= (BL1-EP1)*TF*C1*K1/SIZ E Unit : cg/g EP No. : 1 Temp.Comp. : Off C1 K1

: 1.269 : 1

Factor : 1.006 Conc : 0.1 Blank1

: 47.074

(The above printout data are obtained from titration by AT-510 unit) ≪Titration parameter≫ Form: of titration / APB No. the burette used in titration / Unit No.: APB Unit File number Detector No.: the detector used in titration/ Unit of potential / Max Volume: of titration Wait Time: before titration starts/ Direction.: of titration ≪Control parameter≫ End Point No.: number of EPs / End sense: of EP detection / End Point Area: EP detection area Separation: of potential / Over Titr.Vol. over-titrated volume / Gain: sensitivity of detection signal Data samp.Pot.: potential change of sampling signal / Data samp.Vol. : titration volume of sampling signal Stability: of EP potential / Delay Time: before stability check / Limit Time: of stability check ≪Calculation parameter≫ Calc.Type: of formula / Conc.1 formula 1 / Unit: of results EP No. of calculation / Temp.Comp.: temperature compensation / C1(mg/mL): concentration conversion coefficient K1: unit conversion coefficient / Factor: factor of titration liquid / Blank1: blank level 1

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－Measurement results－ Sample Titration Iodine value n Iodine value (mL) (cg/g) （g） 1 0.3096 23.5860 96.851 Mean 97.205 cg/g 2 0.3122 23.1431 97.855 SD 0.5634 cg/g 3 0.3100 23.5413 96.910 RSD 0.5796 % ＊The above test results are obtained by 3 tests of the same sample. ＊ Red underline shows the data from page 3/4.

10.Summary The iodine value is expressed in grams of iodine for the amount of halogens linked with 100g test sample, and is used as degree of unsaturated bond of fats and oils. Iodine value is used to compare the number of C=C contained in natural complex mixture. Measurement results this time shows favorable repeatability with 0.6% relative standard deviation. Precise and reliable measurement is assured by the automated potentiometry. The iodine value of fats and oils can be perfectly measured by any of the following titration systems manufactured by Kyoto Electronics (KEM).

【AT-610】

Awarded Product of Supreme Technology from Kyoto City • Easy key entry by touch panel of large color LCD （8-inch wide） • Simultaneous titration in parallel • Both potentiometric and Karl Fischer moisture titration (coulometric・volumetric） can be performed at a time.

【AT-510】

• Compact and cost performance model • PC card expands data memory for convenience and versatility.

【AT-500N-1】

• Low cost and high performance • Easy view with back light LCD • GLP/GMP conformed model

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