GB 5009.42-2016 English PDF (GB5009.42-2016)

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GB 5009.42-2016: National Food Safety Standard -- Determination of Table Salt Index
GB 5009.42-2016
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
National Food Safety Standard -
Determination of Table Salt Index
ISSUED ON: AUGUST 31, 2016
IMPLEMENTED ON: MARCH 01, 2017
Issued by: National Health and Family Planning Commission of the PRC
Table of Contents
Foreword ... 3 
1 Scope ... 4 
2 Determination of sodium chloride ... 4 
3 Determination of lead ... 10 
4 Determination of total arsenic ... 13 
5 Determination of cadmium ... 13 
6 Determination of total mercury ... 13 
7 Determination of barium ... 13 
8 Determination of potassium chloride ... 14 
9 Determination of potassium ferrocyanide (ferrous sulfate method) ... 18 
10 Determination of iodine (redox titration method) ... 20 
National Food Safety Standard -
Determination of Table Salt Index
1 Scope
This Standard specifies the testing methods of sodium chloride, lead, total
arsenic, cadmium, total mercury, barium, potassium chloride, potassium
ferrocyanide, and iodine in table salt.
This Standard applies to the determination of table salt index.
2 Determination of sodium chloride
2.1 Determination of water content
Operate according to the direct drying method in GB 5009.3. The drying
temperature is set to 140 °C±2 °C. DRY until the difference between the two
masses before and after does not exceed 5 mg, that is, constant weight.
2.2 Determination of chloride ion
2.2.1 Principle
After the sample is dissolved, USE potassium chromate as an indicator; USE a
silver nitrate standard titration solution to titrate, to determine the content of
chloride ion.
2.2.2 Reagents and materials
Unless otherwise stated, the reagents used in this method are analytically pure;
the water is the Grade 3 water specified in GB/T 6682.
2.2.2.1 Reagents
2.2.2.1.1 Silver nitrate.
2.2.2.1.2 Potassium chromate.
2.2.2.2 Preparation of reagents
2.2.2.2.1 Silver nitrate standard titration solution (0.1 mol/L).
liter (mol/L);
35.453 - The molar mass of chloride ion, in grams per mole (g/mol);
f - The dilution factor of the sample solution;
m - Sample mass, in grams (g);
100, 1000 - Unit conversion factor.
The calculation result is retained to two decimal places.
2.2.6 Precision
The absolute difference between the two independent determination results,
obtained under repeated conditions, shall not exceed 5% of the arithmetic mean.
2.3 Determination of calcium
Operate according to the atomic absorption spectrophotometry in GB/T
5009.92.
2.4 Determination of magnesium
Operate according to GB/T 5009.90.
2.5 Determination of sulfate radical (EDTA complexometric titration)
2.5.1 Principle
Excess barium chloride and the sulfate radical in the sample form insoluble
barium sulfate precipitate. The remaining barium ions are titrated using a
standard solution of disodium edetate (EDTA). USE indirect method to
determine the sulfate radical.
2.5.2 Reagents and materials
Note: Unless otherwise stated, the reagents used in this method are analytically pure; the
water is the Grade 3 water specified in GB/T 6682.
2.5.2.1 Reagents
2.5.2.1.1 Hydrochloric acid.
2.5.2.1.2 Aqueous ammonia.
2.5.2.1.3 Ammonium chloride.
2.5.2.1.4 Absolute ethanol.
2.5.4 Analytical procedures
2.5.4.1 Sample processing
WEIGH 25 g (accurate to 0.001 g) of the pulverized sample in a 400 mL beaker;
ADD about 200 mL of water; HEAT on a boiling water bath; USE a glass rod to
stir until completely dissolved. After cooling, TRANSFER to a 500 mL volumetric
flask; ADD water to the mark; SHAKE well; if necessary, filter. When the content
of ions to be tested in the sample is too high, it may be appropriately diluted
and then determined.
2.5.4.2 Determination
PIPETTE a sample solution (2.5.4.1) of a certain volume (so that the sulfate
radical content in the solution is below 8 mg) in a 150 mL conical flask. ADD 1
drop of hydrochloric acid solution (2.5.2.2.1); ADD 5.00 mL of barium chloride
solution (2.5.2.2.6); STIR for a while; LET it stand for 5 min. ADD 5 mL of
ethylenediaminetetraacetic acid disodium magnesium solution, 10 mL of
absolute ethanol, 5 mL of ammonia-ammonium chloride buffer solution, 4 drops
of chrome black T indicator. USE EDTA standard titration solution to titrate, until
the solution changes from wine red to brilliant blue. RECORD the volume V3 of
EDTA standard titration solution consumed.
Titration of the total amount of calcium-magnesium in the solution: PIPETTE
the sample solution of the same volume as the sulfate radical to be determined;
PLACE it in a 150 mL conical flask. ADD water to 25 mL. ADD 5 mL of ammonia-
ammonium chloride buffer solution, 4 drops of chrome black T indicator. USE
EDTA standard titration solution to titrate, until the solution changes from wine
red to brilliant blue. RECORD the volume V2 of EDTA standard solution
consumed.
2.5.5 Expression of analysis results
The content of sulfate radical in the sample is calculated according to formula
(2):
Where:
X2 - The content of sulfate radical in the sample, %;
V1 - The amount of EDTA standard titration solution used when titrating the
barium chloride solution, in milliliters (mL);
2.6.2 Expression of analysis results
2.6.2.1 Sodium chloride (wet basis)
The content X(w) of sodium chloride (wet basis) in the sample is the sodium
chloride content calculated in accordance with 2.6.1, in %.
The calculation result is retained to two decimal places.
2.6.2.2 Sodium chloride (on a dry basis)
The sodium chloride content in the sample is calculated according to formula
(3):
Where:
X3 - The content of sodium chloride (on a dry basis) in the sample, %;
X(w) - The content of sodium chloride (wet basis) in the sample, %;
P - Water content, %.
The calculation result is retained to two decimal places.
2.6.3 Precision
The absolute difference between the two independent determination results,
obtained under repeated conditions, shall not exceed 10% of the arithmetic
mean.
3 Determination of lead
3.1 Principle
After the sample is treated, the lead ions, at a certain pH, form a complex with
sodium diethyldithiocarbamate (DDTC). It is extracted and separated by 4-
methyl-2-pentanone, introduced into an atomic absorption spectrometer. After
electrothermal atomization, absorb the 283.3 nm resonance line. In a certain
concentration range, the absorption value is directly proportional to the lead
content, in comparative quantification with the standard series.
3.2 Reagents and materials
in a 100 mL volumetric flask; USE nitric acid solution (3.2.2.7) to dilute to the
mark. In such a way, it is diluted several times to a standard use solution
containing 0.0 ng, 5.0 ng, 10.0 ng, 20.0 ng, and 40.0 ng of lead per milliliter,
respectively.
3.3 Instruments and equipment
3.3.1 Atomic absorption spectrometer, with graphite furnace and lead hollow
cathode lamp.
3.3.2 Balance: The sensitivity is 0.001 g.
3.3.3 Adjustable electric hot plate and adjustable electric furnace.
3.4 Analytical procedures
3.4.1 Sample processing
Accurately WEIGH 10 g (accurate to 0.01 g) of sample in a 100 mL beaker;
ADD a small amount of water to dissolve; ADD a small amount of mixed acid
(3.2.2.1); HEAT to boil; LET cool and TRANSFER all to a 50 mL volumetric flask;
DILUTE to the mark; MIX well for use.
3.4.2 Extraction separation
Depending on the sample, PIPETTE 25.0 mL~50.0 mL of the sample solution...