Industrial L-cystine (3)

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With ammonium persulfate a sample of bivalent iron oxidized to trivalent iron, in acid solution with thiocyanate to form a red complex ions, in order to limit visual inspection

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Weigh 1.

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Weigh 2.
000g of the sample (accurate to 0.
001g), and ash it according to the "Method for the Determination of Ash Content" in GB7531.
The burning temperature is 550±25℃
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After cooling, add 0.
5 mL of nitric acid and 2 mL of hydrochloric acid, and put it on a water bath to evaporate to dryness
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The following is measured according to GB7532
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7 Determination of moisture

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7.
1 Analysis steps

Weigh 2.
000g of the sample (accurate to 0.
0002g), and determine the following according to GB6284
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7.
2 Tolerance

The difference between the two parallel determination results is not more than 0.
02%, and the arithmetic mean is the determination result
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8 Determination of ash

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8.
1 Analysis steps

Weigh 2.
000g of the sample (accurate to 0.
001g), the following shall be measured according to GB7531, and the burning temperature shall be 750±25℃
.

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9 Tyrosine test

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9.
1 Principle of the method

The solution of 1-cystine and sulfuric acid formaldehyde becomes grass green after heating, and the solution of L-tyrosine and sulfuric acid formaldehyde becomes dark green after heating
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The identification is performed according to the different colors produced .

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9.
2 Reagents and solutions

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9.
2.
1 Sulfuric acid formaldehyde solution

Take 1mL of formaldehyde solution, add 45mL of water, then add 55mL of sulfuric acid , and mix well
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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.
5min, the solution should be grass yellow, not grass green or dark green
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5 Inspection rules

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1 Industrial L-cystine should be inspected by the quality inspection department of the manufacturer, and the manufacturer should ensure that all products delivered from the factory meet the requirements of this standard
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Each batch of industrial L-cystine should be accompanied by a quality certificate in a certain format, which includes the name and address of the manufacturer, product name, grade, batch number, production date, net weight, product quality certification and this standard.
Standard number
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2 The weight of each batch of products is not more than 2t
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3 Sampling method:

Sampling according to GB6678 and GB6679
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When sampling, use a clean and dry sampling tube to go deep into the upper, middle, and lower parts of the packaging barrel for sampling
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After the sample is mixed and fractionated, the total amount is not less than 200g, divided into 2 clean and dry ground-mouth bottles, and the labels on the bottles indicate: the name of the manufacturer, the name of the product, the batch number and the sampling date
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One bottle is tested and the other bottle is kept for inspection.
The shelf life is one year
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4 If one of the inspection results does not meet the requirements of this standard, samples shall be taken from twice the number of packaging drums for verification
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Even if one of the indicators does not meet the requirements of this standard, the whole batch of products will be unqualified
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5 The user has the right to inspect the industrial L-cystine received in accordance with the provisions of this standard
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6 When there is an objection between the supplier and the buyer on the quality of the product, the arbitration unit can be selected by both parties through consultation and the inspection shall be carried out according to the inspection method specified in this standard
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7 The judgment of the inspection result shall be carried out according to the comparison method of rounding value in GB1250, and the rounding shall be carried out according to GB8170
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6 Packaging, marking, transportation and storage

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1 Industrial L-cystine should be packed in strong iron drums or fiber drums lined with double-layer plastic bags, and the net weight of each drum is 20kg or 25kg
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The allowable error of the weight of each barrel is ±0.
25kg
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2 The packaging barrel shall be painted with a firm mark, which includes: manufacturer name, product name, grade, trademark, batch number and net weight
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3 Industrial L-cystine should be stored in a dry and ventilated warehouse; during transportation, it should be protected from moisture and damage
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