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GB/T 8451-1987 English PDF (GBT8451-1987)

GB/T 8451-1987 English PDF (GBT8451-1987)

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GB/T 8451-1987: Method for limit test of heavy metals in food additives
GB 8451-1987
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
UDC 614.3:543.06:669.3/6
Method for limit test of heavy metals in food additives
ISSUED ON: SEPTEMBER 26, 1987
IMPLEMENTED ON: JULY 01, 1988
Issued by: Ministry of Health of the PRC
Table of Contents
1 Scope ... 3
2 Principle ... 3
3 Reagents ... 3
4 Instruments ... 4
5 Sample treatment ... 4
6 Determination ... 5
Additional notes ... 6
Method for limit test of heavy metals in food additives
1 Scope
This standard applies to the limit test of heavy metals in food additives.
This standard refers to the determination method of heavy metals issued by the Joint
Expert Committee on Food Additives of the Food and Agriculture Organization of the
United Nations and the World Health Organization (FAO/WHO) in 1983.
2 Principle
Under weak acidic conditions (pH 3 ~ 4), heavy metal ions in the sample react with
hydrogen sulfide to produce brown-black, which is compared with the lead standard
solution treated in the same way, to carry out the limit test.
3 Reagents
Unless otherwise specified, the reagents used in this standard are analytically pure
reagents; water is distilled water or deionized water.
3.1 Nitric acid (GB 626-78).
3.2 Sulfuric acid (GB 625-77).
3.3 Hydrochloric acid (GB 622-77).
3.3.1 6 mol/L hydrochloric acid: Measure 50 mL of hydrochloric acid; dilute to 100 mL
with water.
3.3.2 1 mol/L hydrochloric acid: Measure 8.3 mL of hydrochloric acid; dilute to 100
mL with water.
3.4 Ammonia water (GB 631-77).
3.4.1 6 mol/L ammonia water: Measure 40 mL of ammonia water; dilute to 100 mL
with water.
3.4.2 1 mol/L ammonia water: Measure 6.7 mL of ammonia water; dilute to 100 mL
with water.
3.5 pH3.5 acetate buffer: Weigh 25.0 g of ammonium acetate (GB 1292-77); dissolve
it in 25 mL of water; add 45 mL of 6 mol/L hydrochloric acid; adjust the pH to 3.5 with
dilute hydrochloric acid or dilute ammonia water; dilute to 100 mL with water.
3.6 Phenolphthalein indicator solution: 1% ethanol solution.
3.7 Saturated hydrogen sulfide water: Pass hydrogen sulfide gas into water without
carbon dioxide until saturated (this solution is prepared before use).
3.8 Lead standard solution: Weigh 0.1598 g of high-purity lead nitrate (HG 3-1309-80);
dissolve in 10 mL of 1% nitric acid; quantitatively transfer to a 100 mL volumetric flask;
dilute with water to the mark. 1 mL of this solution is equivalent to 1.0 mg of lead.
Dilute 100 times with water before use, so that 1.0 mL is equivalent to 10 μg lead.
3.9 1% nitric acid: Take 1 mL of nitric acid (GB 626-78); dilute to 100 mL with water.
4 Instruments
The glassware used needs to be soaked in 10 ~ 20% nitric acid for more than 24 hours,
rinsed repeatedly with tap water, finally rinsed with water.
4.1 50 mL Nessler colorimetric tube.
5 Sample treatment
Generally, samples can be directly measured according to Chapter 6 "Measurement".
However, if the color of tube A is darker than that of tube C, the samples shall be treated
first. Organic samples must be digested by dry method; then proceed according to 6.1,
6.2, 6.4.
5.1 "Sample treatment" of inorganic samples can be carried out according to the
methods specified in the standard texts.
5.2 "Sample treatment" of organic samples can generally be carried out according to
the following procedures, in addition to those as specified in the standard texts.
5.2.1 Wet digestion: Weigh 5.0 g of sample; place it in a 250 mL Kjeldahl flask or
conical flask; add 10 ~ 15 mL of nitric acid to soak the sample; leave it for a while (or
overnight); heat it slowly; cool it slightly after the effect is relieved; add 5 mL of sulfuric
acid along the wall of the bottle; then heat it slowly until the solution in the bottle begins
to turn brown; continue to add nitric acid (if necessary, add some perchloric acid; be
careful to prevent explosion during the operation). Continue heating until the organic
matter is completely decomposed, until the largest white smoke of sulfur dioxide is
generated; at last the solution shall be dark brown or slightly yellow. After cooling, add
20 mL of water and boil to remove the residual nitric acid, until white smoke is
produced. Do this twice and let it cool. Pipette the solution to a 50 mL volumetric flask;

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