This standard specifies the determination method of phosphorus. This standard is applicable to the determination of phosphorus in infant formula and milk powder. GB/T 5413.22-1997 Determination of phosphorus in infant formula and milk powder GB/T5413.22-1997 Standard download decompression password: www.bzxz.net

GB/T 5413.22—1997
In the past, the determination of phosphorus content in infant formula and milk powder was carried out by molybdenum blue colorimetry. However, the operation steps of this method were complicated, especially the serious loss of phosphorus in sample processing, which resulted in the determination results not accurately reflecting the true content of phosphorus in the sample. The vanadium molybdenum yellow colorimetry given in this standard is simple and fast to operate. The sample processing is changed to wet method to avoid the loss of phosphorus. A large number of tests have proved that the determination results are accurate and reproducible, and the relative error is generally within 3%.
From the date of implementation, this series of standards will replace GB5413—85. 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: 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: Jiang Jindou, Wang Xinxiang, Wang Yun. 312
National Standard of the People's Republic of China
Infant formula and milk powder
Determination of phosphorus
Milk powder and formula foods for infant and young children-Determination of phosphorusScope
This standard specifies the method for the determination of phosphorus.
This standard applies to the determination of phosphorus in infant formula and milk powder. 2 Method Summary
GB/T 5413. 22-1997
Replaces GB 5413--85
After the sample is digested by mixing, it is fixed to volume. In nitric acid solution, phosphorus reacts with ammonium vanadium molybdate to form a yellow complex (P,O·V.Os·22MoO:·3H,O). The depth of the yellow can be determined by colorimetry. The determination range is between 2 and 20μg/mL of phosphorus concentration. 3 Reagents
All reagents, if not specified, are of analytical grade. All experimental water, if not specified otherwise, is grade III water. 3.1 Nitric acid: high grade pure.
3.2 Sulfuric acid, high grade pure.
3.3 Perchloric acid: high grade pure.
3.4 ​​Ammonium vanadium molybdate reagent
Liquid A: 25g ammonium molybdate [(NH.)Mo,O24*4H,O], dissolved in 400mL water. Liquid B: 1.25g ammonium metavanadate (NH,VOs) dissolved in 300mL boiling water, cooled and added with 250mL concentrated nitric acid, then slowly poured liquid A into liquid B, stirring constantly, and diluted with water to 1L, stored in a brown bottle. 3.5 Sodium hydroxide: c(NaOH) is 6mol/L. 3.6 Dinitrophenol indicator: 2g/L
Weigh 0.2g 2,6-dinitrophenol or 2,4-dinitrophenol [CH,OH(NO,),] and dissolve it in 100mL water. 3.7 Standard stock solution: The concentration of phosphorus is 50μg/mL. Weigh 0.2197g of dried potassium dihydrogen phosphate (superior purity), dissolve it in about 400mL water, add 25mL sulfuric acid with a H+ concentration of 12mol/L, and make up to 1L. It can be stored for a long time. 4 Instruments
Common laboratory instruments and:
4.1 Electric heating plate. bzxZ.net
4.2 Spectrophotometer.
Approved by the State Administration of Technical Supervision on May 28, 1997, and implemented on September 1, 1998
5 Operation steps
5.1 Sample treatment
GB/T 5413.22—1997
Accurately weigh 0.5000g of sample into a 125mL conical flask, add a few glass balls, add 10mL concentrated nitric acid (3.1), and then place it on a hot plate for heating reaction. After the violent reaction is over, remove it, cool it slightly, and then add 5mL nitric acid (3.1); 5mL sulfuric acid (3.2) and 5mL perchloric acid (3.3), and place it on the hot plate for heating reaction again. At this time, the temperature should be lowered. If the digestion solution changes, remove it and add 5mL nitric acid (3.1) to continue digestion until the digestion solution becomes colorless or light yellow and emits white smoke. Remove it when there is 3~5mL of digestion solution left, cool it, transfer it quantitatively into a 50mL volumetric flask, and make up the volume with distilled water. This is the test solution. Make a blank at the same time. 5.2 Drawing of standard curve
5.2.1 Accurately draw 0, 2.5, 5, 7.5, 10, 15mL of phosphorus standard stock solution, put it into a 50mL volumetric flask respectively, add color developer to make up the volume, and the phosphorus concentration is 0, 2.5, 5, 7.5, 10, 15ug/mL respectively. 5.2.2 After adding a small amount of water respectively, add 2 drops of dinitrophenol indicator (3.6), adjust to light yellow with sodium hydroxide solution (3.5), then add 10.00mL of ammonium vanadium molybdate reagent (3.4) respectively, and make up the volume with water. Color development at 25-30℃ for 15min. 5.2.3 Use 1cm light path colorimetric blood, wavelength 440nm, measure absorbance value on spectrophotometer, use absorbance value as ordinate and phosphorus content as abscissa to draw standard curve or calculate regression equation. 5.3 Sample determination
Accurately pipette 10mL of sample solution (5.1) (containing 0.2~0.75mg phosphorus) into a 50mL volumetric flask, adjust to zero with blank solution, and the rest of the operation steps are the same as 5.2.2.
6 Expression of analysis results
Phosphorus content in sample (mg/100g) = 9
Where: c—concentration of colorimetric solution obtained from standard curve, ug/mL; V—volume of sample solution (i.e. 50mL),
A dilution factor of sample solution;
mass of sample, g.
7 Allowable difference
m × 1000
The difference between two measured values ​​of the same sample shall not exceed 5% of the average value of the two measurements. 314
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