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Chemical Industry Standard of the People's Republic of China
HG2030—91
Industrial L-Cystine
Published on June 26, 1991
Published by the Ministry of Chemical Industry of the People's Republic of China and implemented on January 1, 1992
Chemical Industry Standard of the People's Republic of China
Industrial L-Cystine
1 Subject Content and Scope of Application
HG2030—91
This standard specifies the technical requirements, test methods, inspection rules, packaging, marking, transportation and storage of industrial L-cystine. This standard applies to industrial L-cystine extracted from hair hydrolysis. This product is mainly used to produce cysteine and raw materials for the food industry, pharmaceutical industry, etc.
, 3,3'-dithiodialanine
Chemical name
Molecular formula CH120,N,S2
Structural formula
S—CH2CH—COOH
SCH2CH-COOH
Relative molecular mass 240.30 (according to the international relative atomic mass in 1987) 2 Reference standards
Chemical reagents
Chemical reagents
Chemical reagents
Preparation of standard solutions for titration analysis (volume analysis) Preparation of standard solutions for impurity determination
Preparation of preparations and products used in test methods Chemical reagents General method for determination of specific optical rotation G B1250
GB6284
GB6678
GB6679
GB7531
GB7532
GB8170
3 Technical requirements
Methods for expressing and determining limit values General method for determining moisture content in chemical products Gravimetric method
General rules for sampling of chemical products
General rules for sampling of solid chemical products
Determination of ash content in organic chemical products
General method for determining heavy metal content in organic products for industrial use Rules for numerical rounding
3.1 Appearance: White hexagonal plate-like crystals or crystalline powder. 3.2 Industrial L-cystine shall meet the requirements of the following table: Approved by the Ministry of Chemical Industry of the People's Republic of China on June 26, 1991 Visual limit method
Implementation on January 1, 1992
Specific rotation[,)
Transmittance, %
L-cystine content, %
Chloride content (as Cl), %
Iron content (as Fe), %
Heavy metal content (as Pb), %
Water content ,%
Ash content,%
Tyrosine test
4 Test method
HG2030—91
Superior product
-215~-225
First-class product
215~—225
Qualified product
-215~～—225
The reagents and water used in this standard, unless otherwise specified, are analytical reagents and distilled water or water of equivalent purity. The standard solutions, preparations and products used in this standard are prepared according to the methods specified in GB601, GB602 and GB603 unless otherwise specified.
4.1 Determination of specific rotation
4.1.1 Reagents
4.1.1.1 Hydrochloric acid solution 9+100.
4.1.2 Analysis steps
Weigh 1.000g (accurate to 0.001g) of the sample dried at 105℃ for 3h, dissolve it in hydrochloric acid solution, transfer it into a 50mL volumetric flask, dilute it to the scale with hydrochloric acid solution, shake it, and measure it according to the provisions of GB613. Temperature correction coefficient: +1.99.
4.2 Determination of transmittance
4.2.1 Reagents and instruments
4.2.1.1 Hydrochloric acid solution: 9+50.
4.2.1.2 Spectrophotometer.
4.2.2 Analysis steps
Weigh 0.500g (accurate to 0.001g) of the sample, dissolve it in 10.0mL hydrochloric acid solution, and measure its transmittance on the spectrophotometer with a 10mm absorption cell and a wavelength of 430nm. At the same time, hydrochloric acid solution is used as reference solution. 4.3 Determination of content
4.3.1 Principle
Bromine can oxidize cystine into α-amino-β-sulfo-propionic acid, and excess bromine can oxidize the iodine ion of potassium iodide into free iodine. The amount of iodine can be determined by iodine titration, so that cystine can be indirectly determined. The reaction is as follows:
KBrOa+5KBr+6HCI3Br2+6KCI+3H20S—CH2CHNH2COOH
S-CH2CHNH2COOH
Br22KI-
-I+2KBr
2NaI+NaSO6
I2+2NaS0
4.3.2 Reagents and solutions
+6H2O-→2HOsS-CH2CHNH2-COOH+10HBr4.3.2.1 Hydroxide Sodium solution: 10g/L; 4.3.2.2 Hydrochloric acid;
4.3.2.3 Potassium iodide solution: 450g/L, prepare when needed; HG2030—91
4.3.2.4 Bromine solution: c(Br2)=0.1mol/L, weigh 3g potassium bromate and 15g potassium bromide, add water to dissolve into 1000mL, store in a brown bottle;
4.3.2.5 Starch solution: 5g/L, freshly prepared; 4.3.2.6 Sodium thiosulfate standard titration solution: c(NazS20s)=0.1mol/L. 4.3.3 Analysis stepsbzxz.net
Weigh 0.3g (accurate to 0.0002g) of the sample dried according to 4.1.2, add 10mL of sodium hydroxide solution to dissolve, transfer to a 100mL volumetric flask, add water to dilute to the mark, and shake well. Pipette 25.0mL of the solution into an iodine volumetric flask, add 50.00mL of bromine solution, add 10mL of hydrochloric acid, immediately cover, shake well, place in a dark place for 10min, then cool in an ice bath for more than 3min, add 5mL of potassium iodide, immediately titrate with sodium thiosulfate standard titration solution until light yellow, add 2mL of starch solution, and continue to titrate until the blue disappears as the end point. Perform a blank test at the same time.
4.3.4 Calculation of analysis results
The content of L-cystine (CsH12O,N,S2) expressed as mass percentage (X) is calculated as follows: X -V) · 0. 024 03 × 100
Wherein: V1——the volume of sodium thiosulfate standard titration solution consumed in blank test, mL; V——the volume of sodium thiosulfate standard titration solution consumed in sample titration, mL; c——the concentration of sodium thiosulfate standard titration solution, mol/L; m——the mass of sample, g;
0.02403——the mass of L-cystine equivalent to 1.00mL sodium thiosulfate standard titration solution Lc (NazS20s) = 1.000mol/L], expressed in grams.
4.3.5 Allowable difference
The difference between the results of two parallel determinations shall not exceed 0.2%, and the arithmetic mean shall be taken as the determination result. 4.4 Determination of chloride content
4.4.1 Principle
Chloride ions and silver ions generate white silver chloride precipitate in acidic solution, which is used for visual turbidimetric limit test. 4.4.2 Reagents and solutions
4.4.2.1 Nitric acid solution: 1+9;
4.4.2.2 Silver nitrate solution: 17g/L;
4.4.2.3 Chloride standard solution: 1mL solution contains 0.1mgCl. 4.4.3 Analysis steps
Weigh 0.100g of the sample (accurate to 0.001g) into a sodium colorimetric tube, add 10mL of nitric acid solution to dissolve, and dilute to 25mL with water. The following is determined according to the "Chloride Test Method" in the Appendix of the Pharmacopoeia of the People's Republic of China. 4.5 Determination of Iron Content
4.5.1 Principle
Ammonium persulfate is used to oxidize the divalent iron in the sample into trivalent iron, which forms a red complex with thiocyanate ions in an acidic solution, and this is used for visual limit testing.
4.5.2 Reagents and Solutions
4.5.2.1 Hydrochloric acid solution: 1 + 4;
4.5.2.2 Hydrochloric acid solution: 1+9;
4.5.2.3 Ammonium persulfate;
4.5.2.4 Ammonium thiocyanate solution: 300g/L; HG2030-91
4.5.2.5 Iron standard solution: 1mL solution contains 0.01mgFe. 4.5.3 Analysis steps
Weigh 1.000g of the sample (accurate to 0.001g) into a sodium colorimetric tube, add hydrochloric acid solution (4.5.2.1) Dissolve 4 mL, add water to 25 mL, and then determine the content according to the Appendix “Iron Salt Test Method” of the Pharmacopoeia of the People’s Republic of China. 4.6 Determination of heavy metal content
4.6.1 Reagents
4.6.1.1 Hydrochloric acid;
4.6.1.2 Nitric acid.
4.6.2 Analysis steps
Weigh 2.000g of the sample (accurate to 0.001g), and ash it according to the "ash determination method" in GB7531, with the ignition temperature being 550±25℃. After cooling, add 0.5mL of nitric acid and 2mL of hydrochloric acid, and evaporate it on a water bath. The following determination is carried out according to GB7532. 4.7 Determination of moisture
4.7.1 Analysis steps
Weigh 2.000g of the sample (accurate to 0.0002g), and the following determination is carried out according to GB6284. 4.7.2 Allowable difference
The difference between the results of two parallel determinations shall not exceed 0.02%, and the arithmetic mean shall be taken as the determination result. 4.8 Determination of ash content
4.8.1 Analysis steps
Weigh 2.000g of the sample (accurate to 0.001g), and perform the following determination according to GB7531. The ignition temperature is selected as 750±25℃. 4.9 Tyrosine test
4.9.1 Principle of the method
L-cystine and sulfuric acid formaldehyde solution are grass green after heating, and L-tyrosine and sulfuric acid formaldehyde solution are dark green after heating. Identification is made based on the different colors generated.
4.9.2 Reagents and solutions
4.9.2.1 Sulfuric acid formaldehyde solution
Take 1mL of formaldehyde solution, add 45mL of water, and then add 55mL of sulfuric acid, and mix well. 4.9.3 Analysis steps
Weigh 0.10g of the sample (accurate to 0.01g), add 1mL of sulfuric acid formaldehyde solution, heat and boil for 0.5 min, the solution should be straw yellow, and should not be straw green or dark green.
5 Inspection rules
5.1 Industrial L-cystine should be inspected by the quality inspection department of the manufacturer, and the manufacturer should ensure that all products leaving the factory meet the requirements of this standard. Each batch of industrial L-cystine leaving the factory should be accompanied by a quality certificate in a certain format, including the name and address of the manufacturer, product name, grade, batch number, production date, net weight, proof that the product quality complies with this standard and the number of this standard. 5.2 The weight of each batch of products shall not exceed 2t.
5.3 Sampling method:
Sampling shall be carried out in accordance with GB6678 and GB6679. When sampling, use a clean and dry sampling tube to sample the upper, middle and lower parts of the packaging barrel. After the sample is mixed and reduced , the total amount is not less than 200, divided into 2 clean dry ground bottles, and the bottles are labeled with: manufacturer name, product name, batch number and sampling date. One bottle is tested and the other bottle is kept for inspection. The shelf life is one year. 5.4 If any of the test results do not meet the requirements of this standard, samples should be taken from twice the number of packaging barrels for verification. Even if one of the indicators in the verification results does not meet the requirements of this standard, the entire batch of products is unqualified. 4
HG2030—91
5.5 The user has the right to inspect the industrial L-cystine received in accordance with the provisions of this standard. When the supply and demand parties have objections to the product quality, the arbitration unit can be selected by negotiation and should be inspected according to the inspection method specified in this standard.
5.7 The judgment of the test results shall be carried out according to the rounded value comparison method in GB1250, and the rounding shall be carried out according to GB8170. 6 Packaging, marking, transportation and storage
6.1 Industrial L-cystine should be packaged in sturdy iron barrels or fiber barrels lined with double-layer plastic bags, with a net weight of 20kg or 25kg per barrel. The allowable error of the weight of each barrel is ±0.25kg.
6.2 The packaging barrels should be painted with firm markings, which include: manufacturer name, product name, grade, trademark, batch number and net weight. 6.3 Industrial L-cystine should be stored in a dry and ventilated warehouse; it should be prevented from moisture and damage during transportation. Additional notes:
This standard was proposed by the Science and Technology Department of the Ministry of Chemical Industry of the People's Republic of China. This standard is under the jurisdiction of the Beijing Chemical Industry Research Institute of the Ministry of Chemical Industry. This standard was drafted by Wuhan Chemical Additives General Factory. The main drafters of this standard are Lin Zhiguo, Shao Wanying and Hu Daozhi. 5
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