This standard specifies the method for determining iodine by gas chromatography. This standard is applicable to the determination of iodine in infant formula and milk powder. GB/T 5413.23-1997 Determination of iodine in infant formula and milk powder GB/T5413.23-1997 Standard download decompression password: www.bzxz.net

GB/T5413.23—1997
The determination of iodine usually adopts spectrophotometry and ion selective electrode method, but the sensitivity is not ideal for the determination of iodine in infant formula and milk powder, which have complex ingredients and high organic matter content. The gas chromatography method adopted in this standard is determined after repeated experiments and verification based on the characteristics of infant formula and milk powder, with reference to a large number of domestic and foreign literatures. It has the characteristics of simple operation, rapidity and high sensitivity.
This series of standards will replace GB5413—85 from the date of implementation. This standard is proposed by China Light Industry General Association.
This standard is under the jurisdiction of the National Dairy Standardization Center. The responsible drafting unit of this standard is the National Dairy Product Quality Supervision and Inspection Center. The participating drafting units of this standard are: 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 are: Yang Jun, Wang Yun, Yang Jinbao. 315
National Standard of the People's Republic of China
Infant formula and milk powder
Determination of iodine
Milk powder and formula foods for infant and young children-Determination of iodine content1 Scope
This standard specifies the method for the determination of iodine by gas chromatography. This standard applies to the determination of iodine in infant formula and milk powder. 2 Summary of Method
GB/T 5413.23—1997
Replaces GB5413-85
After the iodine in the sample is derivatized into an easily vaporized derivative, it is separated by gas chromatography and the iodine content in the sample is quantitatively determined by an electron capture detector.
3 Reagents
All reagents, if the specifications are not specified, refer to analytical grade; all experimental water, if no other requirements are specified, refer to grade tertiary water. 3.1 Taka-Diastase. 3.2 Potassium iodide: spectrally pure.
3.3 Potassium ferrocyanide: c[K,Fe(CN). 3H,O] is 109g/L. Weigh 109g potassium ferrocyanide and dilute to 1000mL volumetric flask with distilled water.
3.4 ​​Zinc acetate: c(ZnAc2) is 219g/L. Weigh 219g zinc acetate and dilute to 1000mL volumetric flask with distilled water. 3.5 Concentrated sulfuric acid.
3.6 Methyl ethyl ketone: chromatographically pure.
3.7 Hydrogen peroxide: volume fraction is 3.5%.
3.8 n-hexane: chromatographically pure.
3.9 Anhydrous sodium sulfate.
3.10 Standard solution
3.10.1 Potassium iodide standard preparation solution: The concentration is 1mg/mL. Accurately weigh 131mg potassium iodide, dissolve it in distilled water and make up to 100mL, and store it in a refrigerator. 3.10.2 Standard intermediate solution:
Take 10mL of the standard stock solution and make up to 100mL, the concentration of which is 100μg/mL; then take 10mL of the aforementioned standard intermediate solution and make up to 100mL, the concentration of which is 10μg/mL.
3.10.3 Potassium iodide standard working solution: The concentration is 2ug/mL. Take 10mL of the standard intermediate solution with a concentration of 10μg/mL and make up to 50mL. Approved by the State Administration of Technical Supervision on May 28, 1997. 316
Implemented on September 1, 1998
4 Instruments
Common laboratory instruments and:
4.1 Separating funnel: 100mL.
4.2 Volumetric flask: 50mL.
4.3 Gas chromatograph. Www.bzxZ.net
4.4 Electron capture detector.
GB/T 5413.23—1997
4.5 Chromatographic column: 2m, 3%0V-101100~200 mesh, 2m long stainless steel column, or column of equivalent performance. 5 Operation steps
5.1 Sample treatment
5.1.1 Starch-containing samples
Accurately weigh 5 g of the sample into a triangular flask, put it into a 50 mL volumetric flask, add 0.5 g of Gaofeng's amylase (3.1), and then add 30 mL of 45-50 ° C distilled water. After mixing evenly, remove the air in the bottle with nitrogen, cover the bottle cap, and place it in a 45 ° C oven for 30 minutes. 5.1.2 Starch-free samples
Accurately weigh 5 g into a beaker, dissolve it with 30 mL of 65 ° C hot water, and transfer it to a 50 mL volumetric flask. 5.2 Preparation of test solution
5.2.1 Add 5 mL of potassium ferrocyanide (3.3) and 5 mL of zinc acetate (3.4) to the above treated sample solution, and dilute to the scale line. Shake it thoroughly and let it stand for 10 minutes.
5.2.2 Filter. Pipette 10mL of filtrate into a 100mL separatory funnel and add 10mL of water. 5.2.3 Add 0.7mL of concentrated sulfuric acid (3.5), 0.5mL of methyl ethyl ketone (3.6), and 2mL of 3.5% hydrogen peroxide (3.7), mix thoroughly, and let stand for 20min.
5.2.4 Add 20mL of n-hexane (3.8) to extract. After standing and layering, transfer the aqueous phase to another separatory funnel and extract again. 5.2.5 Combine the organic phases, add 20mL of water, wash with water, let stand and layer, and discard the aqueous phase. 5.2.6 Dry the organic phase with anhydrous sodium sulfate (3.9), transfer it to a 50mL volumetric flask and make up to volume. This is the test solution. The standard working solution is also prepared according to the above steps. 5.3 Sample determination
5.3.1 Determination conditions
a) Column temperature: 100℃,
b) Injection port temperature: 150℃;
c) Detector ECD temperature 200℃,
d) Injection volume: 2.0μL,
e) Sensitivity: 10-1°;
f) Attenuation: S;
g) Nitrogen flow rate: 20mL/min.
5.3.2 Qualitative determination
Qualitative determination based on retention time. Change chromatographic conditions, such as column temperature and carrier gas flow rate, to change the retention time of the standard component. If a peak in the sample has the same change as the retention time of a peak in the standard sample, it proves that the sample contains the same component as the standard sample.
5.3.3 Quantitative determination
External standard quantitative method.
Inject a certain amount of the standard working solution prepared in step 5.2 into the gas chromatograph to obtain the peak area A of iodine, and inject an equal volume of the sample solution into the gas chromatograph to obtain the peak area B of the sample iodine. 317
6 Expression of analysis results
Wherein: B,
GB/T 5413.23—1997
The iodine content in the sample ((μg/100g) 100×B×c×VA, ×m
The iodine content in the sample) corresponds to the peak area,
The concentration of component i in the standard sample, ug/mL; the total volume of the sample to be tested, mL,
A, the peak area of ​​component i in the standard working solution, m
7 Allowable difference
The mass of a sample, g.
The difference between two measured values ​​of the same sample shall not exceed 5% of the average value of the two measurements. 318
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