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GB 5009.12-2010 English PDF (GB5009.12-2010)

GB 5009.12-2010 English PDF (GB5009.12-2010)

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GB 5009.12-2010: National food safety standard -- Determination of lead in foods

This Standard specifies the method for the determination of lead in foods. This Standard applies to the determination of lead in foods.
GB 5009.12-2010
GB
NATIONAL STANDARD
OF THE PEOPLE REPUBLIC OF CHINA
National food safety standard
Determination of lead in foods
ISSUED ON. MARCH 26, 2010
IMPLEMENTED ON. JUNE 1, 2010
Issued by. Ministry of Health of the PEOPLE Republic of China
Table of Contents
Foreword ... 4
1 Scope ... 5
2 Normative references ... 5
Method 1. Graphite furnace atomic absorption spectrometry ... 5
3 Principle... 5
4 Reagents and materials ... 5
5 Instruments and apparatuses ... 6
6 Analysis procedures ... 7
7 Calculation of results ... 9
8 Degree of precision ... 9
Method 2. Hydride generation atomic fluorescence spectrometry ... 10
9 Principle... 10
10 Reagents and materials... 10
11 Instruments and apparatuses ... 11
12 Analysis procedure ... 11
13 Calculation of results ... 12
14 Degree of precision ... 12
Method 3. Flame atomic absorption spectrometry ... 13
15 Degree of precision ... 13
16 Reagents and materials... 13
17 Instruments and apparatuses ... 13
18 Analysis procedure ... 14
19 Calculation of results ... 15
20 Degree of precision ... 16
Method 4. Disulfide hydrazone colorimetry ... 16
21 Principle... 16
22 Reagents and materials... 16
23 Instruments and apparatuses ... 18
24 Analysis procedure ... 18
25 Calculation of results ... 21
26 Degree of precision ... 22
Method 5. Single-sweep polarography ... 22
27 Principle... 22
28 Reagents and materials... 22
29 Instruments and apparatuses ... 22
30 Analysis procedure ... 23
31 Calculation of results ... 24
32 Degree of precision ... 25
33 Other ... 25
Annex A (Informative) Polarograms of lead in reagent blank control, standard lead solution ... 26
Foreword
This Standard replaces GB/T 5009.12-2003 ?€?Determination of lead in foods?€?. Annex A of this Standard is informative.
The historical versions replaced by this Standard are as follows.
- GB/T 5009.12-1985, GB/T 5009.12-1996, GB/T 5009.12-2003.
National food safety standard
Determination of lead in foods
1 Scope
This Standard specifies the method for the determination of lead in foods. This Standard applies to the determination of lead in foods.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
Method??1.??Graphite??furnace??atomic??absorption??spectrometry
3 Principle
After ashing or acid digestion, the sample is injected into the graphite furnace of atomic absorption spectrophotometer. It then absorbs the resonance line at 283.3 nm after electrothermal atomization. In certain concentration range, the absorption is proportional to lead content, and is used to yield quantitative lead content on the basis of comparison with standard series.
4 Reagents and materials
NOTE Unless otherwise indicated, reagents used in this method are guaranteed reagents; water is the grade one water specified in GB/T 6682.
4.1 Nitric acid. guaranteed reagent.
4.2 Ammonium persulfate.
4.3 Hydrogen peroxide (30%).
6 Analysis procedures
6.1 Sample pretreatment
6.1.1 During sampling and preparation, the sample shall be prohibited from being polluted.
6.1.2 After the removal of impurities, grain and beans are ground, pass through a 20-mesh sieve, and are stored in the plastic bottle for use.
6.1.3 Fresh samples with a high water content such as vegetables, fruit, fish, meat and eggs are processed into homogenate by using food processing
machine or homogenizers, and then stored in the plastic bottle for use. 6.2 Sample digestion (any digestion method can be selected according
to laboratory conditions)
6.2.1 Digestion by pressure digestion tank. 1.00 g ~ 2.00 g of sample
(accurate to 0.001 g, for dry sample and samples with high fat contents, the weight is less than 1.00 g; for fresh sample, the weight is less than 2.0 g; or the weight can be determined in light of operation instructions of the pressure digestion tank) is weighed, placed in polytetrafluorethylene inner tank, and soaked in 2 mL ~ 4 mL of nitric acid (4.1) overnight. Into the system is added 2 mL ~ 3 mL of hydrogen peroxide (4.3) (total volume not exceeding 1/3 of the tank volume). After the inner lid is covered and the stainless steel outer cover is tightened, the tank is then placed in the constant temperature drying oven for 3 h ~ 4 h, which is kept at 120??C ~ 140??C, and then cooled to room temperature naturally in the oven. The digestion solution is washed and transferred into or filtered and transferred into (depending on the salt content of the sample after digestion) a 10 mL ~ 25 mL volumetric flask using a dropper. A small amount of water is used to wash the tank for many times and then transferred into the volumetric flask, to which water is added to the full scale. After that the volumetric flask is shaken to allow the solution to mix evenly. Meanwhile, the reagent is used to provide blank control.
6.2.2 Dry ashing. 1.00 g ~ 5.00 g of sample (accurate to 0.001 g, depending on lead content) is weighed and placed in the porcelain crucible, which is heated on the adjustable electric heating plate with low power until the carbonization produces no smoke. After that, it is transferred into muffle furnace and stays for 6 h ~ 8 h at 500??C??25??C, and then cools to room temperature. A few samples whose ashing process is not complete are added with 1 mL of mixed acid (4.9) and heated on the adjustable electric furnace with low power. The process is then repeated for many times until the completion of the digestion. After that the sample cools to room temperature and dissolves in nitric acid (4.6). The sample digestion solution is washed and transferred into or filtered and transferred into (depending on the salt content of the sample after digestion) a 10 mL ~ 25 mL volumetric flask using a dropper. A small amount of water is used to wash the porcelain crucible for many times and then transferred into the volumetric flask, to which water is added to the full scale. After that the volumetric flask is shaken to allow the even mixing of the solution. Meanwhile, the reagent is used to provide blank control.
6.2.3 Ammonium persulfate ashing method. 1.00 g ~ 5.00 g of sample
(accurate to 0.001 g) is weighed and placed in the porcelain crucible, to which 2 mL ~ 4 mL of nitric acid (4.1) is added to soak the sample for more than 1 h. The sample is carbonized under low power at first. After cooling down, it is covered with 2.00 g ~ 3.00 g of ammonium persulfate (4.2) and continues to be carbonized until no smoke is produced. The sample is transferred to muffle furnace to stay for 2 h at 500??C and 20 min at 800??C, and then cools down. After the addition of 2 mL ~ 3 mL of nitric acid (4.7), the...

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