Powered by Google www.ChineseStandard.net Database: 189759 (21 Apr 2024)

GB 5009.12-2010 (GB5009.12-2010)

Standard IDContents [version]USDSTEP2[PDF] delivered inName of Chinese StandardStatus
GB 5009.12-2010English140 Add to Cart 0-9 seconds. Auto-delivery. National food safety standard -- Determination of lead in foods Obsolete


Standards related to: GB 5009.12-2010

GB 5009.12-2010: PDF in English

GB 5009.12-2010
GB
NATIONAL STANDARD
OF THE PEOPLE’S 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’s 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...
......
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.