This standard specifies the method for the determination of linoleic acid by gas chromatography. This standard is applicable to the determination of linoleic acid in infant formula and milk powder. GB/T 5413.4-1997 Determination of linoleic acid in infant formula and milk powder GB/T5413.4-1997 Standard download decompression password: www.bzxz.net

GB/T5413.4--1997
The previous determination method of linoleic acid only measured the methylated or butylated derivatives of fatty acid triglycerides, excluding the free linoleic acid content. The method given in this standard measures the total amount of linoleic acid, which is relatively simple to handle samples and has high sensitivity. This series of standards will replace GB5413-85 from the date of implementation. This standard is proposed by the China Light Industry Federation.
This standard is under the jurisdiction of the National Dairy Standardization Center. The responsible drafting unit of this standard: National Dairy Quality Supervision and Inspection Center. The participating drafting units of this standard: Food Hygiene Supervision and Inspection Institute of the Ministry of Health, Zhejiang Light Industry Research Institute, Harbin Morinaga Dairy Co., Ltd., Nestle (China) Investment Service Co., Ltd. The main drafters of this standard: Yang Jinbao, Wang Yun, Wang Xinxiang. 237
National Standard of the People's Republic of China
Infant formula foods and milk powder
Determination of linoleic acid
Milk powder and formula foods for infant and young children-Determination of linoleic acid contentScope
This standard specifies the method for the determination of linoleic acid by gas chromatography. This standard is applicable to the determination of linoleic acid in infant formula foods and milk powder. 2 Method Summary
GB/T 5413.4—1997
Replaces GB5413—85
After saponification, free linoleic acid and linoleic acid glyceride in the sample exist in the form of salts. They are extracted with n-hexane under acidic conditions and separated from other components by gas chromatography before their contents are determined. 3 Reagents
All reagents, if not specified, are of analytical grade; all experimental water, if not specified otherwise, is grade tertiary water. 3.1 Petroleum ether: boiling range 40℃～60℃.
3.2 Hexane: chromatographic grade.
3.3 Ethanol: volume fraction 95%.
3.4 ​​Anhydrous sodium sulfate.
3.5 Potassium hydroxide solution: mass ratio 500:1000. 3.6 Sulfuric acid solution: volume fraction 20%. Linoleic acid standard solution: concentration 1mg linoleic acid per ml of hexane. 3.7
4 Instruments
Common laboratory instruments and:
4.1 Separating funnel; 250ml.
4.2 Rotary evaporator.
4.3 Gas chromatograph: with flame ionization detector 4.4 Chromatographic column, 1m×3mm, filled with GP10%SP-216-PS, 100-120 mesh DMCS treated acid washed diatomaceous earth carrier (Su~pelcoport) filler, or columns with equivalent performance. 5 Operation steps
5.1 Accurately weigh 2.0g sample, transfer it into a 250mL flat bottom flask with 10mL water, add 10mL ethanol (3.3), 5mL potassium hydroxide solution (3.5), and reflux for 30min. Shake the flask at least three times during the reflux process to completely saponify the sample. Cool quickly to room temperature. 5.2 Adjust the saponification solution to pH <1.5 with sulfuric acid solution (3.6), transfer the solution to a 250 mL separatory funnel, rinse the flask with at least 20 mL of water several times, and combine the washings in the separatory funnel. Add 25 mL of n-hexane (3.2), shake for 1 min, let stand to separate, collect the n-hexane phase, extract the aqueous phase with n-hexane at least twice, each time using 20 mL. Combine the n-hexane phases. Filter the n-hexane through an anhydrous sodium sulfate column (3.4) into a 100 mL volumetric flask, rinse the column with a small amount of n-hexane, and make up to volume. 5.3 Gas chromatography conditions
Column temperature: 195°C.
Detector temperature: 230°C.
Injector temperature: 250℃.
Injection volume: 2uL.
Detector: flame ionization detector. bzxz.net
Nitrogen flow rate: 20mL/min.
5.4 Determination
Inject 2μL of linoleic acid standard solution and sample solution into the gas chromatograph for qualitative and quantitative determination. 6
Expression of analysis results
The content of linoleic acid in the sample (mg/100g) = Where, Ai--peak area of ​​linoleic acid in the sample; B;-peak area of ​​linoleic acid in the standard solution; C,-concentration of linoleic acid standard solution, mg/mL, m---mass of the sample, g.
7 Allowable difference
A; × C.× 100
The difference between the two measured values ​​of the same sample shall not exceed 5% of the average value of the two measurements. X 100:
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