Some standard content:
GB/T82691998
This standard is the first revision of GB8269-1987 "Citric Acid and Its Test Methods". This revision adds four physical and chemical indicators to the original superior products, namely "sample solution color", "whiteness value", "granularity" and "mechanical impurities".
The physical and chemical indicators of superior products in this standard are equivalent to those of the British Pharmacopoeia (BP-93 Edition), and the United States Pharmacopoeia (USP-23 Edition) is also referenced. The indicators of superior products are equal to or stricter than those of the British Pharmacopoeia (BP-93 Edition), among which moisture, oxalate, iron and heavy metals are stricter than those of the BP-93 Edition, and arsenic salts are stricter than those of the USP-23 Edition. This standard is divided into three grades, superior products are suitable for the pharmaceutical industry, first-class products are suitable for the food industry, and qualified products are industrial grade.
The test methods of this standard refer to the test methods in BP-3 Edition, USP-23 Edition, and the 1995 Edition of the Pharmacopoeia of the People's Republic of China.
This standard was proposed by the China Light Industry Association.
This standard is under the technical jurisdiction of the National Food Fermentation Standardization Center. The drafting units of this standard are: Shanghai Zhongning Biochemical Co., Ltd., Wuxi Zhongya Chemical Co., Ltd., China Food Fermentation Industry Research Institute, Ningxia Fermentation Factory, Shandong Jiejing Group Rizhao Citric Acid Factory. The main drafters of this standard are: Guo Hongchang, Zhou Yage, Zhu Linying, Kang Yongpu, Zhang Yonghua, Fei Hongju. National Standard of the People's Republic of China
Citric acid
Citric acid
GB/T8269—1998
1 Scope
This standard specifies the classification, technical requirements, test methods, inspection rules and marking, packaging, transportation and storage requirements of citric acid.
This standard applies to citric acid (citric acid, chemical name: 2-hydroxytriadicarboxylic acid) obtained by fermentation of starch or sugar raw materials.
2 Referenced Standards
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. When this standard is published, the versions shown are valid. All standards will be revised, and parties using this standard should explore the possibility of using the latest version of the following standards. GB 191—1990
Picture mark for packaging, storage and transportation
GB 601—1988
GB 602—1988
GB 603—1988
GB6061988
Chemical reagentsTitration analysis (volumetric analysis) Preparation of standard solution for chemical reagentsPreparation of standard solution for determination of impurities in chemical reagentsPreparation of preparations and products used in test methods for chemical reagentsGeneral method for determination of water content in chemical reagents (Karl Fischer method)GB/T5009.11—1996Determination of total impurities in foodGB6004-1985Wire woven square mesh for test sievesApproved by the State Administration of Technical Supervision on March 25, 1998Implementation on January 1, 1999
GB/T 8269—1998
GB 8947—1988
GB 9687—1988
3 Classification
3.1 Citric acid monohydrate
Composite plastic woven bags
Sanitary standards for polyethylene molded products for food packagingMolecular formula: CH.O,·H,0
Molecular weight: 210.14
Structural formula: HO
Anhydrous citric acid
Molecular formula: CH:07
Molecular weight: 192.12
Structural formula: HO
4 Technical requirements
4.1 Sensory requirements
COOH·H20
This product is colorless crystals, white crystalline particles (qualified products are slightly yellow) or white crystalline powder; odorless, extremely sour; easily soluble in water and ethanol, slightly soluble in ether; aqueous solution has an acidic reaction. 4.2 Physical and chemical requirements
Physical and chemical requirements should meet the requirements of Table 1.
Superior products
Identification test
Content, %
Clarity
Moisture, %
Easily carbonized matter
Sulfated ash, %
Chloride, %
Sulfate, %
Oxalate, %
Calcium salt, %
Iron, %
Arsenic salt, %
Not darker than the standard
Heavy metals (Pb), %
Sample solution color
Whiteness value, %||tt| |Particle size
Approved by the State Administration of Technical Supervision on March 25, 1998 0.0005
First-class product
Qualified product
Not less than 99.5
Clear or slightly milky
Not deeper than the standard
Not less than 99
Implemented on January 1, 1999
GB/T8269-1998
Mechanical impurities
Note: The water content of anhydrous citric acid should not exceed 0.5%, and other indicators are the same as those of superior products. 5 Test method
The water used in this test refers to distilled water or ion exchange water. Unless otherwise specified, the reagents used in this test are analytically pure. 5.1 Identification test
5.1.1 Apparatus
5.1.1.1 Crucible: 25mL.
5.1.1.2 Stoppered colorimetric tube: 25mL.
5.1.2 Reagents and solutions
5.1.2.1 Sulfuric acid solution (5%): Prepare according to GB603. 5.1.2.2 Mercuric sulfate solution: Weigh 5g of mercuric oxide, add 40mL of water first, then slowly add 20mL of sulfuric acid, stirring while adding, and then add 40mL of water and stir to dissolve. 5.1.2.3 Potassium permanganate solution [c=(1/5KMn0,)=0.1mo1/L], prepare according to GB601. Sodium hydroxide solution (50g/L): Weigh 5g of sodium hydroxide, dissolve in water, and dilute to 5.1.2.4
100mL with water.
5.1.2.5 Pyridine-acetic anhydride solution: Mix pyridine and acetic anhydride in a ratio of 3+1. 5.1.2.6 Citric acid sample solution: Prepare with water, each milliliter contains 5 mg of citric acid. 5.1.3 Test steps
5.1.3.1 Take a small amount of sample in a 25mL crucible and burn it with direct fire. It will slowly decompose, but no caramel smell will occur.
Put 2mL of citric acid sample solution in a 25mL colorimetric tube, adjust to neutrality with 50g/L sodium hydroxide solution, add 1 drop of 5% sulfuric acid, and heat to boiling. Add 1 drop of 0.1mol/L potassium permanganate solution, shake well, and the purple color will fade. Add 1 drop of mercuric sulfate solution to produce a white precipitate. 5.1.3.3 Weigh 5mg of the sample in a 25mL colorimetric tube, add about 5mL of pyridine-acetic anhydride solution, and a yellow to red or purple-red solution will be produced. 5.2 Content
5.2.1 Apparatus
5.2.1.1 Erlenmeyer flask: 150mL.
5.2.1.2 Alkaline burette.
5.2.2 Reagents and solutions
5.2.2.1 Sodium hydroxide standard solution [c(Na0H)=1mo1/L]: Prepare and calibrate according to GB601. 5.2.2.2 Phenol indicator solution (10g/1): Prepare according to GB603. 5.2.3 Test steps
Weigh 1.5g of the sample (accurate to 0.0002g) in a conical flask, add 50mL of water to dissolve, add 3 drops of phenol indicator solution, and titrate with 1mo1/L sodium hydroxide standard solution until the end point is pink. Perform a blank test at the same time.
(v,-vo)xc×0.06404
4×100
mx(1-0.08566)
(vl -V.)xcx 0.06404
Approved by the State Administration of Technical Supervision on March 25, 1998 (1)
·(2)
Implementation on January 1, 1999
GB/T8269-1998
Wherein: Xi
Content of citric acid in water (anhydrous), %; Content of anhydrous citric acid, %;
Volume of sodium hydroxide standard solution consumed in sample titration, mL; Volume of sodium hydroxide standard solution consumed in blank titration, mL; Concentration of sodium hydroxide standard solution, mol/L; Mass of sample, g;
Theoretical content of water in citric acid in water, i.e. 18/210.14=0.08566; Number of grams of anhydrous citric acid equivalent to 1.00mL of sodium hydroxide [c(Na0H)=1.000mol/L] expressed in grams.
5.3 Clarity
5.3.1 Apparatus
Colorimetric tube with stopper: 25mL.
5.3.2 Reagents and solutions
5.3.2.1 Nitric acid solution (13%): prepared according to GB603. 5.3.2.2 Silver nitrate solution (50g/L): Weigh 5g of silver nitrate, dissolve it in water, and dilute it to 100mL with water. This solution should be prepared before use.
5.3.2.3 Sodium chloride solution [c(Na0H)=0.2mol/L]: Weigh 11.6g of sodium chloride that has been burned to constant weight at 500-600℃, dissolve it in water, and dilute it to 1000mL with water. 5.3.2.4
Chloride standard solution I: Take 1mL of 0.2mol/L sodium chloride solution and dilute it to 100mL with water.
Chloride standard solution I: Take 1mL of chloride standard solution I and dilute it to 100mL with water. 5.3.2.5
Reference solution: Prepare according to Table 2 (volume in milliliters). Do not shake violently during preparation. Table 2
Reagent name
Chloride standard solution ⅡI
Nitric acid solution (13%)
Silver nitrate solution (50g/L)
5.3.3 Test steps
Reference solution
Weigh 2g of the sample, put it into a 25mL colorimetric tube, add water to 10mL, and observe the turbidity with the same volume of the newly prepared reference solution under the scattered light of a black background (black bottom plate under the tube rack) for 5 minutes. When the transparency of the sample solution is almost the same as that of the same volume of water, it is called clear. When the milky whiteness of the sample solution is not deeper than that of the reference solution, it is called extremely slightly milky. 5.4 Water
5.4.1 Instrument
Trace moisture tester.
5.4.2 Reagents and solutions
5.4.2.1 Anhydrous methanol: Prepare according to GB606. 5.4.2.2 Karl Fischer reagent: Prepare and titrate according to GB606. 5.4.3 Test steps
Take 20 mL of anhydrous methanol and titrate to the endpoint with Karl Fischer reagent under stirring. Do not record the reading. Then quickly add an appropriate amount of sample (0.1 g of citric acid monohydrate, 1 g of anhydrous citric acid) and continue to titrate to the endpoint.
5.4.4 Calculation
Approved by the State Administration of Technical Supervision on March 25, 1998 and implemented on January 1, 1999
GB/T8269-1998
Where: X The moisture content of the sample, %;
Vz The volume of Karl Fischer reagent consumed during the titration of the sample, mLT The titer of Karl Fischer reagent for water, g/mL; m2 The mass of the sample, g.
5.5 Carbonizable substances
5.5.1 Apparatus
5.5.1.1 Stoppered colorimetric tube: 25 mL.
5.5.1.2 Constant temperature water bath: accuracy is ± 1°C. 5.5.2 Reagents and solutions
5.5.2.1 Hydrochloric acid solution: take 25 mL of hydrochloric acid and dilute to 1000 mL with water. 5.5.2.2 Potassium iodide.
5.5.2.3 Sulfuric acid solution [c(1/2H,S0)=1 mol/L]: prepare according to GB601. (3)
Sodium thiosulfate standard solution [c(NazS,0,)=0.1mol/L]: Prepare and standardize according to GB601 5.5.2.4
Hydrogen peroxide solution (3%): Take 10mL of 30% hydrogen peroxide and dilute to 100mL with water. 5.5.2.5
5.5.2.6 Sodium hydroxide solution (300g/L): Weigh 30g of sodium hydroxide, dissolve it in water, and dilute to 100mL with water.
5.5.2.7 Starch indicator solution (10g/L): Prepare according to GB603. 5.5.2.8 Ferric chloride.
5.5.2.9 Cobalt dichloride.
5.5.2.10 Yellow stock solution: Weigh 46g of ferric chloride and dissolve it in about 900mL of hydrochloric acid solution (5.5.2.1), and then dilute it to 1000mL with this hydrochloric acid solution. When calibrating, adjust this yellow stock solution with hydrochloric acid solution (5.5.2.1) so that it contains 46mg of ferric chloride (FeC13·6H,0) per mL. The solution must be kept away from light and calibrated before use.
Calibration: Take 10mL of the newly prepared ferric chloride solution, add 15mL of water, 4g of potassium iodide, and 5mL of hydrochloric acid, immediately cover the bottle cap, keep it away from light for 15min, add 100mL of water, and titrate the precipitated iodine with 0.1mol/L sodium thiosulfate standard solution until it turns light yellow, add 0.5mL of 10g/L starch indicator solution, and continue titrating to the end point.
Note: Each milliliter of 0.1 mol/L sodium thiosulfate standard solution is equivalent to 27.03 mg of ferric chloride (FeCls·6H20). 5.5.2.11 Red stock solution: Weigh 60 g of cobalt dioxide and dissolve it in about 900 mL of hydrochloric acid solution (5.5.2.1), and then dilute it to 1000 mL with this hydrochloric acid solution. When calibrating, adjust this red stock solution with hydrochloric acid solution (5.5.2.1) so that it contains 59.5 mg of cobalt dichloride (CoC12·6H0) per milliliter. The solution must be stored away from light and calibrated before use.
Calibration: Take 5.0 mL of the newly prepared cobalt dichloride solution, add 5 mL of 3% hydrogen peroxide solution and 10 mL of 300 g/L sodium hydroxide solution, slowly boil for 10 minutes, and cool. Then add 2 g of potassium iodide and 60 mL of 1 mol/L sulfuric acid solution, immediately plug the bottle cap, and shake gently to dissolve the precipitate. The precipitated iodine is titrated with 0.1 mol/L sodium thiosulfate standard solution until it turns light yellow, and 0.5 mL of 10 g/L starch indicator solution is added. The titration is continued until the solution turns pink.
Note: Each mL of 0.1 mol/L sodium thiosulfate standard solution is equivalent to 23.79 mg of cobalt dichloride (CoC12·6H20). 5.5.2.12 Color limit standard solution: Mix the yellow stock solution and the red stock solution in a ratio of 9+1. 5.5.3 Test steps
Approved by the State Administration of Technical Supervision on March 25, 1998, and implemented on January 1, 1999
GB/T 8269-1998
Weigh the sample (0.75g for superior products, 0.5g for first-class products, accurate to 0.01g) into a 25mL stoppered colorimetric tube, add 10mL of sulfuric acid to dissolve, heat in a water bath at 90℃±1℃ for 1min, shake to mix well, continue to heat in a water bath at 90℃±1℃ for 1h, take out, and cool rapidly (cool with ice water when it is hot). Pipette 10mL of the color limit standard solution (5.5.2.12) into another 25mL stoppered colorimetric tube, and compare visually with white as the background. The color of the sample tube shall not be darker than that of the standard tube. 5.6 Sulfate ash
5.6.1 Apparatus
5.6.1.1 Crucible: quartz or platinum.
5.6.1.2 Desiccator (use color-changing silica gel as desiccant). 5.6.1.3 Balance: sensitivity 0.1 mg.
5.6.1.4 High temperature furnace.
5.6.2 Reagents
Sulfuric acid.
5.6.3 Test procedure
Weigh 2 g of the sample (accurate to 0.0002 g) in a quartz or platinum crucible and slowly burn until it is completely carbonized. Let it cool, add 0.5-1.0 mL of sulfuric acid to moisten it, heat it at low temperature until the sulfuric acid fumes are completely removed, and burn it in a high temperature furnace at 700-800℃ until it is completely carbonized and the weight is constant. 5.6.4 Calculation
m-mo×100
Where: X is the sulfated ash content, %;
-the mass of the crucible, g;
the mass of the sample and crucible after ignition, g;
5.7 Chloride
5.7.1 Apparatus
The mass of the sample and crucible before ignition, g.
Colorimetric tube with stopper: 25mL.
5.7.2 Reagents and solutions
5.7.2.1 Nitric acid solution (13%): Same as 5.3.2.1. (4)
5.7.2.2 Silver nitrate solution [c(AgNO3)=0.1mol/L]: Prepared according to GB603. 5.7.2.3 Chloride standard solution I (containing 0.1g/L of chlorine): Prepared according to GB602. 5.7.2.4 Chloride standard solution II (containing 0.01 g/L chlorine): Pipette 10 mL of chloride standard solution I and dilute to 100 mL with water.
5.5.2.5 Chloride standard solution III (containing 0.005 g/L chlorine): Pipette 5 mL of chloride standard solution I and dilute to 100 mL with water.
5.5.2.6 Sodium hydroxide [c(Na0H)=2 mol/L]: Prepare according to GB601. 5.7.2.7 Citric acid sample solution: Weigh 5 g of the sample (accurate to 0.1 g), add 39 mL of 2 mol/L sodium hydroxide solution to dissolve, and dilute to 50 mL with water. 5.7.3 Test steps
Pipette 10 mL of citric acid sample solution into a 25 mL stoppered colorimetric tube, add 5 mL of water, then add 1 mL of 13% nitric acid solution, and immediately add 0.1mL of 1mol/L silver nitrate solution, stand for 2min in dark, and compare the turbidity with the standard tube horizontally under a black background. The milkiness shall not exceed that of the standard tube prepared by the following method.
Approved by the State Administration of Technical Supervision on March 25, 1998..com Implemented on January 1, 1999
GB/T82691998
Preparation of standard tube: When determining superior, first-class, and qualified citric acid, take 10mL of chloride standard solution IIII, IIII, and I respectively, add 5mL of water, and perform the same treatment as the above sample tube. 5.8 Sulfate
5.8.1 Instrument
5.8.1.1 Stoppered colorimetric tube: 50mL.
5.8.1.2 Beaker: 50mL
5.8.2 Reagents and solutions
5.8.2.1 Hydrochloric acid solution (6 mol/L): Prepare according to GB601. 5.8.2.2 Barium chloride solution (250 g/L): Weigh 25 g of barium chloride, dissolve it in water, and dilute it to 100 mL with water. 5.8.2.3 Acetic acid (30%): Prepare according to GB603. 5.8.2.4 Ethanol solution (30%): Measure 313 mL of ethanol (96%) and dilute it to 1000 mL with water. 5.8.2.5 Potassium sulfate ethanol solution (0.0181 g/L): Weigh 0.0181 g of potassium sulfate and dilute it to 100 mL with ethanol solution (5.8.2.4).
5.8.2.6 Sulfate standard solution (containing sulfate 0.01g/L): aspirate 1.0mL of 0.0181g/L potassium sulfate ethanol solution and dilute to 100mL with ethanol solution (5.8.2.4). 5.8.3 Test steps
Weigh the sample (2g for superior products, 1g for first-class products, weigh to 0.01g) in a 50mL beaker, add 30mL of water to dissolve, this solution is the sample solution. Take two 50mL stoppered colorimetric tubes, add 1mL of 250g/L chlorinated sodium solution, then add 1mL of sulfate standard solution, shake, and let stand for 1min. Aspirate 15mL of sample solution into one colorimetric tube, aspirate 15mL of sulfate standard solution into the other colorimetric tube, then add 1mL of 6mol/L hydrochloric acid solution and 0.5mL of 30% acetic acid solution to each, shake well, after 5min, the milky whiteness of the sample tube shall not be deeper than that of the standard tube. 5.9 Oxalate
5.9.1 Apparatus
5.9.1.1 Stoppered colorimetric tube: 25mL.
5.9.1.2 Test tube: 15mm×180mm.
5.9.2 Reagents and solutions
5.9.2.1 Hydrochloric acid.
Phenylhydrazine hydrochloride solution (10g/L): Prepare according to GB603. 5.9.2.34
Potassium ferrocyanide solution (50g/L): Weigh 5g potassium ferrocyanide, dissolve in water, and dilute to 100mL with water.
Zinc granules.
5.9.2.5 Oxalic acid solution I (0.25g/L): Weigh 0.175g oxalic acid (C,H,04·2H,0), dissolve in water, and dilute to 500mL with water.
5.9.2.6 Oxalic acid solution II (0.25 g/L): Take 50 mL of oxalic acid solution I and dilute it to 250 mL with water. 5.9.3 Test steps
Weigh the sample (2 g for superior products, 0.4 g for first-class products, accurate to 0.01 g) in a test tube, add 4 mL of water, 3 mL of hydrochloric acid and 1 g of zinc granules, boil for 1 min, and let stand for 2 min. Transfer to a test tube containing 0.25 mL of hydrochloric acid-benzoic acid solution, heat to boiling, cool rapidly, pour into a 25 mL stoppered colorimetric tube, add an equal volume of hydrochloric acid and 0.25 mL of 50 g/L potassium ferricyanide solution, shake, let stand for 30 min, and compare visually with the standard tube prepared as follows. The pink color produced by the sample tube shall not be darker than that of the standard tube. Preparation of standard tubes: Pipette 4 mL of oxalic acid solution IⅡ and oxalic acid solution I into two stoppered colorimetric tubes respectively, and perform the same treatment as the above sample tubes. 5.10 Calcium
Approved by the State Administration of Technical Supervision on March 25, 1998..comImplementation on January 1, 1999
GB/T8269-1998
5.10.1 Apparatus
Stoppered colorimetric tube: 25 mL.
5.10.2 Reagents and solutions
5.10.2.196% ethanol.
5.10.2.2 Acetic acid solution (2 mol/L): Measure 118 mL of glacial acetic acid and dilute it to 1000 mL with water. Acetic acid solution (6 mol/L): Measure 350 mL of glacial acetic acid and dilute it to 1000 mL with water. 5.10.2.3 Ammonium oxalate solution (40 g/L): Weigh 4 g of ammonium oxalate, dissolve it in water, and dilute it to 100 mL with water.
5.10.2.4 Calcium standard solution I (containing 1 g/L calcium): Weigh 2.5 g of calcium carbonate dried at 105~110℃, add 12 mL of 6 mol/L acetic acid to dissolve it, and dilute it to 1000 mL with water. 5.10.2.5 Calcium standard solution I (containing 0.01 g/L calcium): Take 1 mL of calcium standard solution I, and dilute it to 100 mL with water.
5.10.2.6 Calcium ethanol standard solution (containing 0.1 g/L calcium): Take 10 mL of calcium standard solution I, and dilute it to 100 mL with 96% ethanol solution.
5.10.2.7 Sample solution: Take 5 mL of citric acid sample solution (5.7.2.7), and mix it with 10 mL of water. 5.10.3 Test steps
Put 0.20mL of calcium ethanol standard solution and 1mL of 40g/L ammonium oxalate solution in a colorimetric tube. After 1 minute, add 1mL of 2mol/L acetic acid solution and 15mL of sample solution, shake well, and place for 15 minutes. Visually compare the turbidity with the standard tube prepared by the following method. The milkiness shall not exceed that of the standard tube. Preparation of standard tube: Pipette 1mL of 40g/L ammonium oxalate solution and 10mL of calcium standard solution II, add 1mL of 2mol/L acetic acid solution and 5mL of water, shake well, and compare the turbidity after 15 minutes. 5.11
5.11.1 Apparatus
Colorimetric tube with stopper: 25mL
5.11.2 Reagents and solutions
5.11.2.1 Sulfuric acid solution [c(1/2H2S0)=1mol/L]: Same as 5.5.2.3. 5.11.2.2 Citric acid sample solution: Same as 5.7.2.7. 5.11.3 Test steps
Pipette 5mL of citric acid sample solution (5.7.2.7) into a colorimetric tube with stopper, add 5mL of 1mol/L sulfuric acid solution, and leave for 1 hour. Visually compare the turbidity with another reference tube containing citric acid sample solution and 5mL of water. The opalescence of the tube shall not exceed that of the reference tube. 5.12 Iron
5.12.1 Apparatus
Colorimetric tube with stopper: 100mL.
5.12.2 Reagents and solutions
5.12.2.1 Hydrochloric acid solution (6 mol/L): Same as 5.8.2.2.5.12.2.2 Ammonium persulfate solution (10 g/L): Weigh 1 g of ammonium persulfate, dissolve it in water, and dilute it to 100 mL with water.
5.12.2.3 Ammonium thiocyanate solution (80 g/L): Weigh 8 g of ammonium thiocyanate, dissolve it in water, and dilute it to 100 mL with water.
5.12.2.4 n-Butanol.
Iron standard solution I (containing 0.1 g/L of iron): Prepared according to GB602. 5.12.2.5
5.12.2.6 Iron standard solution I (containing 0.01 g/L of iron): Take 10 mL of iron standard solution I and dilute it to 100 mL with water.
Approved by the State Administration of Technical Supervision on March 25, 1998, and implemented on January 1, 1999
GB/T8269-1998
5.12.3 Test steps
Weigh 1g of the sample (accurate to 0.001g), add 35mL of water to dissolve, then add 3mL of 24% hydrochloric acid solution, 3mL of 10g/L ammonium persulfate and 3mL of 80g/L ammonium thiocyanate solution, then dilute to 50mL with water, shake well, add 20mL of n-butanol, shake to separate, and visually compare the color with the standard tube prepared by the following method. The color of the alcohol layer in the sample tube shall not be darker than that of the standard tube. Preparation of standard tube: Take 1mL of iron standard solution II I and treat it in the same way as the sample tube. 5.13 Arsenic
Determine according to the second method in GB/T5009.11-1997. 5.14 Heavy metals
5.14.1 Apparatus
Colorimetric tube with stopper: 50 mL.
5.14.2 Reagents and solutions
5.14.2.1 Dilute acetic acid: Take 6 mL of glacial acetic acid and dilute to 100 mL with water. 5.14.2.2 Ammonia water.
Phenol butter indicator: Same as 5.2.2.2.
5.14.2.4 Saturated aqueous hydrogen sulfide solution: Prepared according to GB603. 5.14.2.5 Lead standard solution I (containing 0.1 g/L lead): Prepared according to GB602. 5.14.2.6 Lead standard solution II (containing 0.01 g/L lead): Pipette 10 mL of lead standard solution I and dilute to 100 mL with water. bzxz.net
5.14.3 Test steps
Weigh 4 g of the sample (accurate to 0.0001 g) in a 50 mL stoppered colorimetric tube, dissolve with appropriate amount of water, add 2 drops of phenolic indicator solution, neutralize with ammonia water to a slightly reddish color, add 2 mL of dilute acetic acid, and then dilute to 25 mL with water. Add 10 mL of saturated aqueous hydrogen sulfide solution to this sample tube and the standard tube prepared according to the following method at the same time, shake well, place in a dark place for 10 minutes, and perform visual colorimetry. The color of the sample tube shall not be darker than that of the standard tube. Preparation of standard tube: Pipette 2.0 mL of lead standard solution IⅡI into a 50 mL stoppered colorimetric tube, add 2 mL of dilute acetic acid, dilute to 25 mL with water, and perform the same treatment as the sample tube. 5.15 Sample solution color
5.15.1 Instrument
Stoppered colorimetric tube: 25 mL.
5.15.2 Reagents and solutions
5.15.2.1 Yellow stock solution: Same as 5.5.2.10. 5.15.2.2 Red stock solution: Same as 5.5.2.11. 5.15.2.3 Copper sulfate.
5.15.2.4 Acetic acid solution (2 mol/L): Same as 5.10.2.2. 5.15.2.5 Hydrochloric acid solution (1%): Measure 12 mL of hydrochloric acid and dilute to 1000 mL with water. 5.15.2.6 Blue stock solution: Weigh 63g of copper sulfate and dissolve it in about 900mL of hydrochloric acid solution (5.5.2.1), then dilute it to 1000mL with this hydrochloric acid solution. When calibrating, adjust this blue stock solution with hydrochloric acid solution (5.5.2.1) so that each milliliter contains 62.4mg of copper sulfate (CuS04·5H20). The solution must be stored away from light and calibrated before use.
Calibration: Take 10.0mL of the newly prepared copper sulfate solution, add 50mL of water, 12ml of 2mol/L acetic acid and 3g of potassium iodide, add 0.5mL of starch indicator solution (5.5.2.7), and titrate with 0.1mol/L sodium thiosulfate standard solution (5.5.2.4) until it is slightly light brown. Note: Each milliliter of 0.1mol/L sodium thiosulfate standard solution is equivalent to 24.97mg of copper sulfate (CuS0·5H20). 5.15.2.7 Preparation of standard solutions
Approved by the State Administration of Technical Supervision on March 25, 1998..comImplementation on January 1, 1999
GB/T 82691998
Use yellow stock solution, red stock solution and blue stock solution to prepare three standard solutions, see Table 3. Table
Standard solutions
BY (yellow-brown)
Y (yellow)
GY (yellow-green)
Red solution, mL
Yellow solution, mL
5.15.2.8 Preparation of reference solutions
Use the three standard solutions to prepare the following reference solutions, See Table 44
Reference solution
Standard solution, mL
BY (yellow brown) 2.5
Y (yellow) 2.5
Blue solution, mL
1% hydrochloric acid, mL
1% hydrochloric acid, mL
GY (yellow green) 0.75
5.15.2.9 Citric acid sample solution: Weigh 10g of the sample, dissolve it in water, and dilute it to 50mL with water. 5.15.3 Test steps
Prepare the reference solution with the standard solution immediately before the determination. Pipette 10mL of the sample solution, water and reference solution into 25mL stoppered colorimetric tubes respectively. Under scattered light, with white as the background, observe the colorimetric tube vertically and compare the chromaticity of the sample solution. If the chromaticity of the sample solution is the same as that of water or not darker than that of the reference solution, it is considered qualified. 5.16 Whiteness value
5.16.1. Instrument
5.16.1.1 Whiteness tester: integrating sphere diameter 150mm; adopt d/o illumination observation geometry (IS02469); zero drift not more than 0.1; indication error not more than 0.5: repeatability error not more than 0.1; mirror reflection error not more than 0.1.
5.16.1.2 Standard sieve: SSW0.25/0.2. 5.16.2 Test steps
Before the test, adjust the instrument according to the method described in the instruction manual of the whiteness tester. Sieve the citric acid sample, take the sample that passes SSW0.25/0.2 and place it evenly in the sampler, flatten the sample surface with a smooth glass plate, and measure its whiteness value.
5.17 Particle size
5.17.1. Instrument:
Standard sieve: SSW1.4/0.630.
5.17.2 Test steps
5.17.2.1 Visually observe whether there are sticky blocks in the sample and the finished product in the packaging bag. 5.17.2.2 Weigh 100g of the sample and put it into the standard sample sieve. Repeat the vertical and horizontal cycles, shake the sieve for 5 minutes or start the electric sample divider for 5 minutes, weigh the sample that passes the standard sieve, and calculate the percentage. When the weight percentage of the sample particles is greater than or equal to 90%, the particle size is considered to be uniform and meets the screening test. 5.18 Mechanical impurities
5.18.1 Instrument
5.18.1.1 Beaker: 50mL.
5.18.1.2 Buchner funnel: No. 9.
5.18.1.3 Medium-speed quantitative filter paper.
5.18.2 Test steps
Visually observe that there is no foreign matter larger than 0.5mm.
Weigh 5g of the sample into a 50mL beaker and add 10mL of water to dissolve it. Pour the solution into a No. 9 funnel and filter it by suction. Visually observe the foreign matter smaller than 0.5mm on the filter paper, and the count value is less than or equal to 5.
6 Inspection rules
6.1 Batch
Products produced with the same raw materials, the same process, the same specifications, the same batch number packaging, and with the same quality certificate are considered a batch.
6.2 Sample size
Take samples according to Table 5.
Batch range, bag
151~500
6.3 Sampling
Sample size, bag
Insert the sampling needle into 3/4 of each sample and take no less than 100g of sample. The total sample volume for each batch shall be no less than 2kg. Mix the sample quickly, divide it into quarters, and put it into two dry, clean wide-mouth bottles respectively, and label them. One copy shall be subjected to physical and chemical analysis, and the other copy shall be retained for future reference. 6.4 Delivery inspection
6.4.1 Before the product leaves the factory, the technical inspection department of the manufacturer shall be responsible for the batch inspection according to the provisions of this standard. Only the products that meet the requirements of the standard and are issued with a quality certificate can leave the factory. 6.4.2 Delivery inspection items
Content, clarity, moisture, easily carbonizable matter, chloride, sulfate, oxalate, calcium salt, salt, iron, sample liquid color, whiteness value, particle size, mechanical impurities. 6.5 Routine inspection
6.5.1 Routine inspection items
In addition to the delivery inspection items, there are also identification tests, sulfated ash, arsenic salts, and heavy metals. 6.5.2 Under normal circumstances, routine inspections must be carried out once every 3 months, and must also be carried out in any of the following circumstances.
a) Changes in major raw and auxiliary materials;
b) Changes in key processes and equipment;
c) When new trial-produced products or normal production products are suspended for more than 3 months and then resume production: d) The national quality supervision agency proposes a requirement for routine inspections. 6.6 Judgment rules
6.6.1 When one of the inspection items fails in the inspection results, two times the amount of samples should be taken from the same batch of products for re-inspection, and the re-inspection results shall prevail. If one item fails, the entire batch shall be judged as unqualified. 6.6.2 If the re-inspection results do not meet the physical and chemical index requirements of "superior products" or "first-class products" marked on the label, but meet the requirements of the next level, it can be downgraded. 6.6.3 When the supply and demand parties have objections to the product quality, the arbitration unit shall be selected by negotiation and re-inspection shall be carried out in accordance with this standard.
7 Marking, packaging, transportation and storage
7.1 The inner packaging of citric acid products shall be food polyethylene bags and double-layer kraft paper bags or double-layer food polyethylene bags (the inner packaging materials shall comply with GB9687). The outer packaging shall be composite plastic woven bags (the outer packaging materials shall comply with GB8947).
Approved by the State Bureau of Technical Supervision on March 25, 1998 and implemented on January 1, 1999
GB/T82691998
7.2 The packaging bag should indicate: product name, manufacturer name, address, specifications, date of manufacture (batch number), registered trademark, net weight, implementation standard number and grade, and should be accompanied by a quality inspection certificate. 7.3 Packaging quality requirements: The inner liner bag must be tightly sealed and must not be breathable, and the outer packaging must not be contaminated. The net content of each bag is 25kg, 50kg, and the allowable error is ±0.5%.
7.4 During transportation, this product is strictly prohibited from being mixed, stored, or transported with toxic, harmful, corrosive items, odorous, or colored powders.
7.5 This product should be stored in a clean, cool, dry, and ventilated warehouse and should not be piled in the open air. Approved by the State Bureau of Technical Supervision on March 25, 1998 and implemented on January 1, 1999
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