Some standard content:
ICS 67.040
National Standard of the People's Republic of China
GB/T5009.76--2003
Replaces GB/T8450--1987
Determination of arsenic in food additives
Determination of arsenic in food additivesIssued on August 11, 2003
Ministry of Health of the People's Republic of China
Standardization Administration of the People's Republic of China
Implementation on January 1, 2004
GB/T5009.76—2003
This standard replaces GB/T8450-1987 "Determination of arsenic in food additives". Compared with GB/T8450-1987, this standard has been modified as follows: the Chinese name of the standard has been modified and changed to "Determination of Arsenic in Food Additives"; the structure of the original standard has been modified in accordance with GB/T20001.4-2001 "Standard Writing Rules Part 4: Chemical Analysis Methods".
This standard is proposed and managed by the Ministry of Health of the People's Republic of China. This standard is drafted by the Yangzhou Municipal Health and Epidemic Prevention Station of Jiangsu Province. The main drafters of this standard are Jiang Youfu, Jiang Qing'an, Yang Yichao, and Zhang Liuping. The original standard was first issued in 1987, and this is the first revision. 556
1 Scope
Determination of Arsenic in Food Additives
This standard specifies the limit test and quantitative test methods for arsenic in food additives. This standard applies to the limit test and quantitative test of arsenic in food additives. Method 1: Silver diethylcyanodithiocarbamate colorimetric method 2 Principle
GB/T 5009.76--2003
In the presence of potassium iodide and stannous chloride, the high-valent arsenic in the sample solution is reduced to trivalent arsenic. The trivalent arsenic reacts with the new ecological hydrogen produced by zinc particles and acid to generate arsine hydrogen gas. After the interference of hydrogen sulfide is removed by lead acetate cotton, it is absorbed and reacted with silver diethylaminodithiocarbamate solution dissolved in triethanolamine-chloroform or pyridine to generate a purple-red complex and is quantitatively compared with the standard. 3 Reagents
3.1 Nitric acid.
3.2 Sulfuric acid.
3.2.1 Sulfuric acid (1+1) solution: Slowly add 1 volume of concentrated sulfuric acid to 1 volume of water and use it after cooling. 3.2.2 Sulfuric acid (1 mol/I) solution: Measure 28 mL of concentrated sulfuric acid, slowly add it into water, and dilute it to 500 mL with water. 3.3 Hydrochloric acid
3.4 20% sodium hydroxide solution.
3.5 Magnesium oxide.
3.6 15% magnesium nitrate solution.
3.7 15% potassium iodide solution, store in a brown bottle (prepare before use). 40% stannous chloride solution: Weigh 20 g of stannous chloride (SnCl2·2H.O) and dissolve it in 50 mL of hydrochloric acid. 3.84
3.9 Lead acetate cotton: Soak the absorbent cotton in 10% lead acetate solution, take it out and dry it after 2 hours. 3.10 Zinc without a monument.
Chloroform. bzxZ.net
Pyridine.
3.13 Absorption liquid A: Weigh 0.25g of silver diethylaminodithiocarboxylate, grind it and dissolve it in an appropriate amount of chloroform. Add 1.0mL of triethanolamine and dilute it to 100mL with chloroform. Let it stand for filtration into a brown bottle and store it in a refrigerator for later use. 3.14 Absorption liquid B: Weigh 0.50g of silver diethylaminodithiocarboxylate, grind it and dissolve it in pyridine and dilute it to 100mL with pyridine. Let it stand for filtration into a brown bottle and store it in a refrigerator for later use. 3.15 Phenolphthalein: 1% ethanol solution.
3.16 Arsenic standard solution: Weigh 0.1320g of arsenic trioxide (As2O.) dried to constant weight in a sulfuric acid dryer and dissolve it in 5mL of 20% sodium hydroxide solution. After dissolution, add 25mL 1mol/L sulfuric acid, transfer to a 1000mL volumetric flask, and dilute to the mark with freshly boiled and cooled water. 1.00ml of this solution is equivalent to 0.100mg. Before use, take 1.0ml., add 1mL 1mol/L sulfuric acid to a 100mL volumetric flask, and dilute to the mark with freshly boiled and cooled water. 1.0mL of this solution is equivalent to 1.0μg arsenic. 4 Instruments
4.1 Spectrophotometer.
GB/T5009.76—2003
4.2 Arsenic measurement device (see Figure 1).
Outer diameter 10
Gas outlet
4.2.1-100mL～150mL conical flask (A) (No. 19 standard port). Unit is millimeter
5mL scale
00. 5 ~ 1. c
4.2.2 Air guide tube (B): The tube mouth is the standard mouth No. 19, and there should be no air leakage when it is tightly fitted with the conical flask A. The diameter of the tube tip is 0.5mm1.0mm, and the joint with the absorption tube C is the standard mouth No. 14. After insertion, the distance between the tube tip and the bottom of the tube C is 1mm~2mm. 4.2.3 Absorption tube (C): The tube mouth is the standard mouth No. 14, 5ml scale, and the height is not less than 8cm. The material of the absorption tube should be consistent. 5 Sample treatment
5.1 The "sample treatment" of inorganic samples can be carried out according to the methods specified in the various standard texts. 5.2 In addition to the provisions of the various standard texts, the "sample treatment" of organic samples is generally carried out according to the following procedures. 5.2.1 Wet digestion: Weigh 5.00g of sample, place in a 250mL Kjeldahl flask or conical flask, add 10mL nitric acid to soak the sample, place for a while (or overnight), slowly heat, wait for the effect to ease, cool slightly, add 5mL sulfuric acid along the wall of the flask, and slowly heat until the solution in the flask begins to turn brown, continue to add nitric acid (if necessary, add some perchloric acid, but be careful to prevent explosion) until the organic matter is completely decomposed, continue to heat, and a large amount of sulfur dioxide white smoke is generated. The solution should be colorless or slightly yellow. After cooling, add 20mL of water and boil, remove the residual nitric acid until white smoke is generated. Do this twice, let cool, transfer the solution to a 50mL volumetric flask, wash the Kjeldahl flask or conical flask with a small amount of water 2 to 3 times, add the washing solution to the volumetric flask, add water to the scale, and each 10mL of sample solution is equivalent to 1.0g of sample. Take the same amount of nitric acid and sulfuric acid, and do a reagent blank test according to the above method. 5.2.2 Dry ash method: This method is used for samples that are not suitable for wet digestion. Take 5.0g of sample in a porcelain crucible, add 10mL of 15% magnesium nitrate solution, add 1g of magnesium oxide powder, mix well, soak for 4h, and heat at low temperature 558°C or steam on a water bath, heat with low heat until carbonization is complete, move the crucible to a high-temperature furnace, burn at below 550°C until ashization is complete, take it out after cooling, add appropriate amount of water to moisten the ash, add a few drops of phenol anhydride solution, and then slowly add hydrochloric acid (1+1) solution until the phenolic acid red color fades, then transfer the solution to a 50mL volumetric flask (filter if necessary), wash the crucible 3 times with a small amount of water, add the washing solution to the volumetric flask, add water to the scale, and mix well. Each 10ml of sample solution is equivalent to 1.0g of sample. Take the same amount of magnesium oxide and magnesium nitrate, and perform a reagent blank test according to the above method. 6 Determination
6.1 Selection of absorption liquid
The choice of absorption liquid A (3.13) or absorption liquid B (3.14) can be determined according to the needs of analysis. However, during the determination process, the same absorption liquid should be used for the sample, blank and standard. 6.2 Limit test
6.2.1 Take a certain amount of sample solution and arsenic limit standard solution (arsenic content is not less than 5ug), place them in arsenic generating bottle A respectively, add sulfuric acid to a total of 5mL, and add water to 50mL.
6.2.2 Add 3mL of 15% potassium iodide solution to each of the above bottles, mix, and let stand for 5min. Add 1ml of 40% stannous chloride solution respectively, mix well, and let stand for another 15min. Add 5g of arsenic-free metallic zinc to each sample, immediately plug the airway tube B filled with lead acetate cotton, and insert the tip of tube B into the absorption tube C containing 5.0mL absorption solution A or absorption solution B. React at room temperature for 1h, remove absorption tube C, and add chloroform (absorption solution A) or pyridine (absorption solution B) to make up the volume of absorption solution to 5.0mL. 6.2.3 Measure the absorbance of the absorption solution at a wavelength of 515nm (absorption solution A) or 540nm (absorption solution B) by visual colorimetry or using a 1cm colorimetric cup. The chromaticity or absorbance of the sample solution shall not exceed the chromaticity or absorbance of the arsenic limit standard absorption solution. If the sample has been treated, the arsenic limit standard should also be treated in the same way. 6.3 Quantitative determination
6.3.1 Take 25mL (or appropriate amount) of sample solution and the same amount of reagent blank solution, place them in arsenic generation bottle A, add sulfuric acid to a total of 5mL, add water to 50mL, and mix.
6.3.2 Take 0.0, 2.0, 4.0, 6.0, 8.0, 10.0mL of arsenic standard solution (1.0mL is equivalent to 1.0ug of arsenic), place them in arsenic generation bottle A,Add water to 40 mL and then add 10 mL sulfuric acid (1+1) solution, mix well. 6.3.3 Add 3 mL of 15% potassium iodide solution to the sample solution, reagent blank solution and arsenic standard solution, mix well, let stand for 5 minutes, then add 1 mL of 40% stannous chloride solution, mix well, let stand for 15 minutes, then add 5 g of metal zinc, immediately plug the airway tube B filled with lead acetate cotton, and insert the tip of tube B into the absorption tube C containing 5.0 mL of absorption liquid A or absorption liquid B, react at room temperature for 1 hour, remove the absorption tube C, and use trimethylmethane (absorption liquid A) or pyridine (absorption liquid B) to add the absorption liquid volume to 5.0 mL. Use a 1 cm colorimetric cup, adjust the instrument zero point with a zero tube at a wavelength of 515 nm (absorption liquid A) or 540 nm (absorption liquid B), measure the absorbance, and draw a standard curve for comparison. If the sample has been treated, the arsenic standard series should also be treated in the same way to calibrate the standard curve. 7 Calculation of results
C= (ml-m2)×1 000
×1000
Wherein:
C Arsenic content in the sample, in milligrams per kilogram (or milligrams per liter) [mg/kg (or mg/L); ml——the mass of arsenic in the sample solution, in microgram (μg); m2i
the mass of arsenic in the reagent blank solution, in microgram (μg); sample mass (volume), in grams (or milliliters) [g (or mL); n
Vi—the volume of the sample after treatment, in milliliters (mL); V2—the volume of the sample solution taken during the determination, in milliliters (mL). 559
GB/T 5009.76—2003
8 Principle
Method 2 Arsenic spot method
In the presence of potassium iodide and stannous chloride, the high-valent arsenic in the sample solution is reduced to trivalent arsenic. The trivalent arsenic reacts with zinc particles and acid to produce new ecological hydrogen to generate arsenic hydrogen gas. The interference of hydrogen sulfide is removed by lead acetate cotton, and then it is combined with mercuric bromide test paper to generate yellow to orange spots. The limit test is compared with the standard arsenic spot.
9 Reagents
9.1 The same as 3.1~~3.10 and 3.15 in the diethylamino diformic acid silver colorimetric method. 9.25% mercuric bromide ethanol solution.
9.3 Mercuric bromide test paper: Cut a circular filter paper with a diameter of 2 cm, immerse it in 5% mercuric bromide ethanol solution for more than 1 hour, store it in a refrigerator, and take it out and put it in a dark place for use before use. 10 Instruments
Arsenic test device: see Figure 2.
- Conical flask;
rubber stopper,
3. Test tube
tube mouth;
glass.
10.1 100mL conical flask.
10.2 Rubber stopper: there is a hole in the middle.
10.3 Glass arsenic test tube: total length 18cm, thick at the top and thin at the bottom, the inner diameter from the tube mouth to 14cm is 6.5mm, and it gradually narrows from there, the inner diameter of the end is about 1mm to 3mm, there is a hole 1cm near the end, the diameter is 2mm, the narrow part is tightly inserted into the rubber stopper, so that the lower part extends to the small hole just below the rubber stopper. The upper part is thicker and filled with lead acetate cotton. The length is 5cm to 6cm, and the distance from the upper end to the tube mouth is at least 3cm. The top of the arsenic test tube is a round flat tube mouth, which is polished on the upper side and has a hook on each side of the lower side for fixing the glass cap. 10.4 Glass cap: The lower side is polished, with a crescent-shaped groove on the upper side and a round hole in the center, with a diameter of 6.5mm. When using, cover the glass cap on the tube mouth of the arsenic tube so that the round holes fit each other, sandwich a mercuric bromide test paper in the middle, and fix the glass cap to the arsenic test tube with a rubber ring or other appropriate methods. 560
GB/T5009.76—2003
Take a certain amount of sample solution and arsenic limit standard solution (containing arsenic 1.0μg or 2.0μg), place them in conical flasks respectively, add 5mL hydrochloric acid (if the sample solution contains sulfuric acid or hydrochloric acid, subtract the milliliters of acid contained in the sample solution), add water to 30mL, then add 5mL 15% potassium iodide solution, 5 drops of 40% stannous chloride solution, mix well, and place at room temperature for 10 minutes. Add 3g of arsenic-free metallic zinc to each of the above conical flasks, and immediately plug the arsenic test tube pre-filled with lead acetate cotton and mercuric bromide test paper, place at 25℃ for 1h, take out the arsenic spot for comparison, and the sample spot shall not be deeper than the arsenic spot of the arsenic limit standard. If the sample has been treated, the arsenic limit standard should also be treated in the same way. 561
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