GB 1886.9-2016National food safety standard - Food additives - Hydrochloric acid (English PDF)

2.1 Molecular formula

HCl

2.2 Relative molecular mass

36.46 (according to 2007 international relative atomic mass)

3.1 Sensory requirements

Sensory requirements shall meet the requirements of Table 1.

3.2 Physical and chemical indicators

Physical and chemical indicators shall meet the requirements of Table 2.

Annex A

Inspection methods

A.1 Safety warning

WARNING -- Hydrochloric acid is highly corrosive. Operators shall take appropriate safety and health measures. Contact personnel shall wear protective equipment such as protective glasses and acid-resistant gloves.

Some reagents in this test method are toxic or corrosive. Care shall be taken when handling. If splashed on skin, rinse immediately with water. Severe cases shall be treated immediately.

A.2 General provisions

The reagents and water used in this Standard refer to analytically pure reagents and grade three water specified in GB/T 6682 unless other requirements are specified. The standard solutions used in reagents, standard solutions for impurity determination, preparations and products shall be prepared in accordance with the provisions of GB/T

601, GB/T 602 and GB/T 603 unless other requirements are specified. The solution used in the test refers to the aqueous solution when the solvent is not specified.

A.3 Identification test

A.3.1 Reagents and materials

A.3.1.1 Silver nitrate solution: 2g/L.

A.3.1.2 Ammonia solution: 2+3.

A.3.1.3 Methyl orange indicator solution: 1g/L.

A.3.2 Identification method

A.3.2.1 Measure 1mL of specimen into 50mL of water. Add the silver nitrate solution dropwise, resulting in a white milky precipitate. It can be dissolved in ammonia solution.

It is insoluble in nitric acid.

A.3.2.2 Measure 1mL of specimen into 100mL of water. Add 2 drops of methyl orange solution. The solution turns red. This aqueous solution is strongly acidic.

A.4 Determination of total acidity (as HCl)

A.4.1 Method principle

The specimen solution uses bromocresol green as the indicator solution. Titrate with sodium hydroxide standard titration solution until the solution changes from yellow to blue as the end point. The reaction formula is as follows:

A.4.2 Reagents and materials

A.4.2.1 Sodium hydroxide standard titration solution: c(NaOH)=1mol/L.

A.4.2.2 Bromocresol green indicator solution: 1g/L.

A.4.3 Instruments and equipment

A.4.3.1 Conical flask: 100mL (with ground stopper).

A.4.3.2 Burette: 50mL, level A, with 0.1mL division value.

A.4.4 Analysis steps

A.4.4.1 Specimen

Measure about 3mL of specimen. Place in a conical flask that contains about 15mL of water and has been weighed (accurate to 0.0001g). Mix and weigh (to the nearest

0.0001g).

A.4.4.2 Determination

Add 2~3 drops of bromocresol green indicator solution to the specimen. Titrate with sodium hydroxide standard titration solution until the solution changes from yellow to blue as the end point.

A.4.5 Result calculation

The mass fraction w1 of total acidity (calculated as HCl) is calculated according to formula (A.1):

Where,

V - The volume of sodium hydroxide standard titration solution consumed in the titration, in milliliters (mL);

1000 - Conversion factor;

A.5.4.5 Determination

A.5.4.5.1 Add water to the specimen to about 20mL. Use ammonia water to adjust the pH of the solution to 2~3. Then add 1mL of hydroxylamine hydrochloride solution,

5mL of acetic acid-sodium acetate buffer solution and 2mL of 1,10-phenanthroline solution. Use water to dilute to the scale. Shake well. Let stand for 15min.

A.5.4.5.2 Use a suitable cuvette. At the wavelength of 510nm, use a blank solution to adjust the zero point of the spectrophotometer. Measure the absorbance of the solution.

A.5.5 Result calculation

The mass fraction w2 of iron content (calculated as Fe) is calculated according to formula (A.2):

Where, m2 - The mass of the specimen, in grams (g);

10-6 - Conversion factor;

m3 - The mass of iron in the specimen obtained from the standard curve or calculated by the linear regression equation, in micrograms (µg);

10/100 - Conversion factor.

Take the arithmetic mean of the parallel determination results as the report result. The absolute value of the difference between the parallel determination results is not more than 0.0001%.

A.6 Determination of sulfate (as SO4)

A.6.1 Method principle

Evaporate the specimen to dryness. Use hydrochloric acid solution to dissolve the residues. Use glycerol-ethanol mixture as stabilizer. Add barium chloride to make suspension. Use the spectrophotometer to determine the absorbance of the suspension.

A.6.2 Reagents and materials

A.6.2.1 Barium chloride dihydrate (BaCl2·2H2O).

A.6.2.2 Glycerol-ethanol mixture: 1+2.

adjust the zero point of the spectrophotometer. Measure the absorbance of the solution.

A.6.4.1.5 Draw a standard curve or calculate a linear regression equation with the sulfate content (mg) as the abscissa and the corresponding absorbance as the ordinate.

A.6.4.2 Specimen

Weigh about 20g of specimen (accurate to 0.01g). Put in an evaporating dish. Evaporate to dryness on a steam bath. Cool to room temperature. Add 3mL of hydrochloric acid solution to dissolve the residues. Transfer all into a 50mL volumetric flask. Add 5mL of glycerol-ethanol mixture. Use water to dilute to the scale. Shake well.

A.6.4.3 Blank test

No specimen is added. Use the exact same analytical steps, reagents and dosage as the test specimen to carry out the blank test..

A.6.4.4 Determination

A.6.4.4.1 Carefully move the specimen into a dry beaker containing 0.3g of barium chloride dihydrate. Shake for 2min at a speed of 2r/s. At room temperature, let stand for

10min.

A.6.4.4.2 Use a suitable cuvette. At the wavelength of 450nm, use blank solution to adjust the zero point of the spectrophotometer. Measure the absorbance of the solution.

A.6.5 Result calculation

The mass fraction w3 of sulfate (calculated as SO4) is calculated according to formula (A.3):

Where, m5 - The mass of sulfate in the sample obtained from the standard curve or calculated by the linear regression equation, in milligrams (mg);

1000 - Conversion factor;

m4 - The mass of specimen, in grams (g).

Take the arithmetic mean of the parallel determination results as the report result. The absolute value of the difference between the parallel determination results is not more than 0.001%.

A.7 Determination of free chlorine (as Cl)

A.7.1 Method principle

Add potassium iodide solution to sample solution. Precipitate iodine. Use starch as indicator liquid. Titrate the free iodine with a standard titration solution of sodium thiosulfate. The reaction formulas are as follows:

A.7.2 Reagents and materials

A.7.2.1 Hydrochloric acid. The oxidizing or reducing substances contained in

hydrochloric acid shall be less than 0.0002%.

A.7.2.2 Potassium iodide solution: 150g/L.

A.7.2.3 Standard titration solution of sodium thiosulfate: c(Na2S2O3)=0.1mol/L.

A.7.2.4 Starch indicator solution: 10g/L. This solution can only be kept for two weeks.

A.7.3 Instruments and equipment

A.7.3.1 Conical flask: 500mL (with ground stopper).

A.7.3.2 Microburette.

A.7.4 Analysis steps

A.7.4.1 Specimen

Measure about 50mL of specimen. Place in a conical flask filled with about 100mL of water and weighed (accurate to 0.01g). Cool to room temperature. Weigh (accurate to

0.01g).

A.7.4.2 Blank test

Do not add specimen. Replace the specimen with an equal amount of hydrochloric acid.

Use the exact same analytical steps, reagents and dosage as the test specimen to carry out the blank test.

A.7.4.3 Determination

Add 7mL of potassium iodide solution to the specimen. Put the stopper tightly and shake. Let stand for 2min in the dark. Add 1mL of starch indicator solution. Titrate with sodium thiosulfate standard titration solution until the blue color of the solution disappears as the end point.

100mL volumetric flask. Dilute to the scale. Shake well. This solution is prepared before use.

A.8.2.4 Starch indicator solution: 10g/L.

A.8.3 Instruments and equipment

General laboratory equipment.

A.8.4 Determination

Measure 1mL of hydrochloric acid (A.8.2.1). Place in a 30mL test tube. Dilute to 20mL with freshly boiled and cooled water. Add 1mL of potassium iodide solution, 1mL of starch indicator solution and 2mL of iodine standard solution. Shake well. Add 1mL of specimen to the test tube. The blue color of the solution will not disappear.

A.9 Determination of non-volatile matter

A.9.1 Method principle

Evaporate a certain amount of specimen to dryness. Keep constant weight. Weigh.

A.9.2 Instruments and equipment

General laboratory equipment.

A.9.3 Analysis steps

Weigh about 5g of specimen (accurate to 0.01g). Transfer to an evaporating dish that has been weighed (accurate to 0.0001g). Evaporate dry on steam bath. Dry at 110°C for

1 h. Cool to room temperature in a desiccator. Weigh (accurate to 0.0001g).

A.9.4 Result calculation

The mass fraction w5 of non-volatile matter is calculated according to formula (A.5):

Where, m8 - The mass of the nonvolatile matter, in grams (g);

m7 - The mass of the specimen, in grams (g).

Take the arithmetic mean of the parallel determination results as the report result. The absolute value of the difference between the parallel determination results is not more than 0.005%.

A.10 Determination of Arsenic (As)

A.10.1 Determination of arsenic diethyldithiocarbamate silver spectrophotometry

A.10.1.1 Method principle

In acidic medium, use potassium iodide and stannous chloride to reduce As5+ to As3+.

Add zinc particles. React with acid to generate new ecological hydrogen. Further reduce

As3+ to arsine. It is absorbed by silver diethyldithiocarbamate [Ag(DDTC)]pyridine solution. Generate a purple-red colloidal solution. Use the spectrophotometer to measure the absorbance. The reaction formula is as follows:

A.10.1.2 Reagents and materials

A.10.1.2.1 Hydrochloric acid.

A.10.1.2.2 Arsenic trioxide.

WARNING -- Arsenic trioxide is a highly toxic drug.

A.10.1.2.3 Zinc particles: particle size is 0.5mm~1mm.

A.10.1.2.4 Potassium iodide solution: 150g/L.

A.10.1.2.5 Stannous chloride hydrochloric acid solution: 400g/L. Weigh 40.0g of stannous chloride dihydrate (SnCl2·2H2O). Dissolve in the solution mixed by 25mL of water and 75mL of hydrochloric acid.

A.10.1.2.6 Arsenic standard stock solution: 1mL of the solution contains 0.1mg of arsenic (As). Weigh 0.132g of arsenic trioxide dried to constant mass in a sulfuric acid desiccator. Warm and dissolve in 1.2mL of sodium hydroxide solution (100g/L).

Transfer to a 1000mL volumetric flask. Dilute to the scale.

A.10.1.2.7 Arsenic standard solution: 1mL of solution contains 2.5µg of arsenic (As).

Pipette 25mL of arsenic standard stock solution (A.10.1.2.6). Place in a 1000mL volumetric flask. Use water to dilute to the scale. Shake well. This solution is prepared when it is required.

A.10.1.2.8 Diethyldithiocarbamate silver pyridine solution: 5g/L. Weigh 1.0g of silver diethyldithiocarbamate. Dissolve in pyridine. Use pyridine to dilute to 200mL. The solution is kept in a tightly closed amber glass bottle. It is valid for two weeks.

A.10.1.2.9 Lead acetate cotton.

A.10.1.3 Instruments and equipment

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