GB/T 5413.21-1997 Determination of calcium, iron, zinc, sodium, potassium, magnesium, copper and manganese in infant formula and milk powder
Some standard content:
GB/T5413.21---1997
The determination of metal content generally adopts chemical method and atomic absorption spectrometry, but due to the cumbersome operation of chemical method, many interference factors, poor reproducibility of the results of some items, etc., atomic absorption spectrometry is still widely used. This standard is equivalent to the method of the American Association of Public Analytical Chemists (AOAC). The sample treatment in the determination is simple and the reproducibility is good. 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 Sanitation 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: Wang Xinxiang, Jiang Jindou, Wang Yun, Sun Tao, Yuan Shuo. 308
National Standard of the People's Republic of China
Milk powder and formula foods for infant and young children-Determination of calcium, iron, zinc, sodium, potassium, magnesium, copper and manganese1Scope
GB/T 5413.21—1997
Replaces GB5413—85
This standard specifies the method for the determination of potassium, sodium, calcium, magnesium, zinc, iron, copper and manganese by atomic absorption spectrophotometry. This standard is applicable to the determination of potassium, sodium, calcium, magnesium, zinc, iron, copper and manganese in various infant formula foods and milk powder. 2 Method Summary
After the sample is dry-ashed and the organic matter is decomposed, acid is added to dissolve all the inorganic ions in the ash, and the sample is directly atomized in the air-acetylene flame, and the absorption of potassium, sodium, calcium, magnesium, zinc, iron, copper and manganese atoms on specific wavelength spectra is measured in the optical path. When measuring calcium and magnesium, lanthanum is used as a release agent to eliminate the interference of phosphoric acid and the like. 3 Reagents
The experimental water is secondary water, and the reagents are all high-grade pure. 3.1 Concentrated hydrochloric acid.
3.2 Salt: volume fraction is 2%.
3.3 Hydrochloric acid: volume ratio 1*4.
3.4 Nitric acid: volume ratio 1*1.
3.5 Lanthanum solution: the concentration of La is 50g/L. Weigh 29.32g of lanthanum oxide (La20,) and moisten it with 25mL of deionized water. Slowly and carefully add 125mL of concentrated hydrochloric acid to dissolve the lanthanum oxide, and dilute to 500mL with deionized water. 3.6 Potassium standard stock solution: K+ mass concentration 1000μg/mL. Weigh 1.9067g of dried potassium fluoride (molecular weight 74.55, spectrally pure), dissolve it with hydrochloric acid (3.2), and dilute it to a 1000mL volumetric flask.
3.7 Sodium standard stock solution, Na+ mass concentration 1000μg/mL.
Weigh 2.5420g of dried sodium chloride (molecular weight 58.44, spectrally pure), dissolve it with hydrochloric acid (3.2), and dilute it to a 1000mL volumetric flask. 3.8 Calcium standard stock solution: Ca+2 mass concentration 1000μg/mL. Weigh 2.4963 g of dry calcium carbonate (molecular weight 100.05, spectrally pure), dissolve it in 100 mL of hydrochloric acid (3.3), and dilute it to a 1000 mL volumetric flask.
3.9 Magnesium standard stock solution: Mg+2 mass concentration 1000 μg/mL. Weigh 1.0000 g of pure magnesium (spectrally pure), dissolve it in 40 mL of nitric acid (3.4), and dilute it to a 1000 mL volumetric flask with water. Approved by the State Administration of Technical Supervision on May 28, 1997, implemented on September 1, 1998
GB/T 5413.21—1997
3.10 Zinc standard stock solution: Zn+2 mass concentration 1000 μg/mL. Weigh 1.0000g of metallic zinc (spectrally pure), dissolve it in 40mL of nitric acid (3.4), and dilute it to a 1000mL volumetric flask with water. 3.11 Iron standard preparation solution: The mass concentration of Fe+3 is 1000μg/mL. Weigh 1.0000g of metallic iron powder (spectrally pure), dissolve it in 40mL of nitric acid (3.4), and dilute it to a 1000mL volumetric flask with water. 3.12 Copper standard stock solution: The mass concentration of Cu+2 is 1000μg/mL. Weigh 1.0000g of metallic copper (spectrally pure), dissolve it in 40mL of nitric acid (3.4), and dilute it to a 1000mL volumetric flask with water. 3.13 Manganese standard stock solution: The mass concentration of Mn+2 is 1000μg/mL. Weigh 1.0000g of metallic manganese (spectrally pure), dissolve it in 40mL of nitric acid (3.4), and dilute it to a 1000mL volumetric flask with water. 3.14 Standard intermediate solution of each ion: the mass concentration is 100ug/mL. Pipette 25mL of the standard stock solutions of 3.6, 3.7, 3.8, 3.9, 3.10, 3.11, 3.12 and 3.13 into eight 250mL volumetric flasks, and dilute to volume with hydrochloric acid (3.2) to obtain the standard intermediate solutions of the above ions. 4 Instruments
Common laboratory instruments and:
4.1 Atomic absorption spectrophotometer.
4.2 Hollow cathode lamps for potassium, sodium, calcium, magnesium, zinc, iron, copper and manganese. 4.3 Cylinder acetylene gas and air compressor.
4.4 Quartz crucible or porcelain crucible.
4.5 High temperature furnace.
5 Operation steps
5.1 Standard curve
5.1.1 Preparation of standard mixed solution
Prepare three mixed standard working solutions according to the volumes given in Table 1. That is, take 10mL of copper and manganese standard intermediate solution (3.14) respectively and dilute to volume in a 100mL volumetric flask, that is, the mass concentration of the two ions is 10μg/mL, and then take the solution according to Table 1. When determining the content of iron and zinc, take the standard intermediate solution (3.14) in a 100mL volumetric flask according to Table 1; dilute to volume with hydrochloric acid (3.2) to obtain 5 copper, manganese, iron and zinc mixed standard solutions: when determining the content of calcium and magnesium, take the standard intermediate solution (3.14) in a 100mL volumetric flask according to Table 1, add 2mL of lanthanum solution and dilute to volume with hydrochloric acid (3.2) to obtain calcium and magnesium standard mixed solution. When determining the content of potassium and sodium, follow the calcium and magnesium steps to obtain potassium and sodium standard mixed solution. The concentrations of each element are shown in Table 2. Table 1 Volume of standard intermediate solution of each element used to prepare mixed standard solution mL
Table 2 Concentration of each element in mixed standard solution
μg/mL
5.1.2 Drawing of standard curve
GB/T 5413. 21—1997
According to the instrument manual, adjust the instrument working conditions to the best state for determining each element, and select sensitive absorption lines K 766.5nm Ca 422.7nm Na 588.9nm, Mg 285.2nm.Fe 248.3nm, Cu 324.7nm, Mn 279.5nm.Zn 213. 9mm. After adjusting and preheating the instrument, use a capillary to spray hydrochloric acid (3.2) solution. When determining potassium, sodium, calcium and magnesium, use 2% hydrochloric acid (HCI) containing 1g/L by volume to adjust the zero. Determine the transmittance of each ion in the mixed standard solution, and draw a standard curve or calculate the regression equation for the content of each element. 5.2 Sample treatment
Accurately weigh 5.0000g of sample in (4.4), carbonize it on a low fire on an electric furnace until no smoke is released, and then move it into a high-temperature furnace (4.5) and heat it to 490°C to ash the sample into a white ash. If there are black carbon particles, after cooling, add a small amount of 1:1 nitric acid (3.4) to moisten it. After evaporating it on a low fire on an electric furnace, move it into a 490°C high-temperature furnace and continue to ash it into a white ash. Take it out, cool it to room temperature, add 5mL of 1:4 hydrochloric acid, heat it on an electric furnace to fully dissolve the ash, cool it to room temperature, move it into a 50mL volumetric flask, make up to volume with deionized water, and treat a blank sample at the same time.
5.3 Determination of samples
After adjusting the instrument to the optimal state and zeroing it with the corresponding hydrochloric acid solution (3.2), determine the transmittance of the sample and the reagent blank in the following manner.
5.3.1 Determination of sodium
Pipette 1mL from 50mL of sample solution into a 100mL volumetric flask, add 2mL of lanthanum solution, make up to volume with hydrochloric acid (3.2), and determine on the instrument. 5.3.2 Determination of potassium
Pipette 10mL from the 100mL volumetric flask used for sodium determination into a 50ml. volumetric flask, add 1mL of solution, make up to volume with hydrochloric acid (3.2), and determine on the instrument.
5.3.3 Determination of calcium and magnesium
Pipette 1mL from 50mL of sample solution into a 50mL volumetric flask, add 1mL of lanthanum solution, make up to volume with hydrochloric acid (3.2), and determine on the instrument. 5.3.4 Determination of iron, manganese, zinc and copper
Pipette 5 mL from 50 mL sample solution into a 25 mL volumetric flask, dilute with hydrochloric acid (3.2), and measure zinc on the machine. For iron, manganese and copper, use 50 mL sample solution to measure directly on the machine.
6 Expression of analysis results
Element content in sample (mg/100g) = (c1-% × 4 × 100m X 1000
Where: cr—concentration of element in the test solution, μg/mL; c2—concentration of element in the test blank solution, μg/ml; V—volume of sample solution, mL; wwW.bzxz.Net
A—dilution factor of sample solution;
m—mass of sample, g.
7 Allowable difference
The difference between two measured values of the same sample shall not exceed 5% of the average value of the two measurements. (1)
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