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GB 5009.12-2017 (GB5009.12-2017)

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GB 5009.12-2017
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
National Food Safety Standard –
Determination of Lead in Foods
ISSUED ON. APRIL 6, 2017
IMPLEMENTED ON. OCTOBER 6, 2017
Issued by. National Health and Family Planning Commission of the
People’s Republic of China;
China Food and Drug Administration.
Table of Contents
Foreword ... 4 
1 Application Scope ... 5 
2 Principle ... 5 
3 Reagents and Materials ... 5 
4 Apparatus ... 6 
5 Analytical Procedure ... 7 
6 Expression of Analytical Results ... 8 
7 Accuracy ... 9 
8 Others ... 9 
9 Principle ... 9 
10 Reagents and Materials ... 9 
11 Apparatus ... 11 
12 Analytical Procedure ... 11 
13 Expression of Analytical Results ... 12 
14 Accuracy ... 13 
15 Others ... 13 
16 Principle ... 13 
17 Reagents and Materials ... 13 
18 Apparatus ... 15 
19 Analytical Procedure ... 16 
20 Expression of Analytical Results ... 17 
21 Accuracy ... 17 
22 Others ... 17 
Annex A Temperature Rise Procedure for Microwave Digestion ... 18 
Annex B Reference Conditions for Graphite Furnace Atomic Absorbance
Spectrometer ... 19 
Annex C Reference Conditions for Flame Atomic Absorption Spectrometer
... 20 
Foreword
This Standard replaces the determination of lead in GB 5009.12-2010, National Food
Safety Standard – Determination of Lead in Foods, GB 20380.3-2006, Starch and
Derived Products – Heavy Metals Content – Part 3. Determination of Lead Content by
Atomic Absorbance Spectrometry with Electrothermal Atomization, GB 23870-2009,
Determination of Pb in Propolis – Microwave Digestion – Graphite Furnace Atomic
Absorbance Spectrophotometry, GB/T 18932.12-2002, Method for the Determination
of Potassium, Sodium, Calcium, Magnesium, Zine, Iron, Copper, Manganese,
Chromium, Lead, Cadmium Contents in Honey – Atomic Absorbance Spectrometry,
NY/T 1100-2006, Determination of Lead, Cadmium in Rice – Graphite Furnace Atomic
Absorbance Spectrometry, SN/T 2211-2008, Determination of Lead, Cadmium in
Royal Jelly – Graphite Furnace Atomic Absorbance Spectrometry Method.
Compared with GB/T 5009.12-2010, the major changes of this Standard are as follows.
-- it keeps wet digestion and pressure tank digestion in pretreatment method,
deletes dry ashing and ammonium persulfate ashing method, and adds
microwave digestion;
-- it keeps graphite furnace atomic absorbance spectrometry as the first method and
adopts ammonium dihydrogen phosphate-palladium nitrate solution as matrix
modifier; keeps flame atomic absorbance spectrometry as the third method; and
keeps dithizone colorimetry as the fourth method;
-- it adds inductively coupled plasma mass spectrometry as the second method;
-- it deletes hydride generation atomic fluorescence spectrometry, single-sweep
polarography;
-- it adds the instrument reference conditions for microwave digestion temperature
rise procedure, graphite furnace atomic absorbance spectrometry and flame
atomic absorbance spectrometry.
National Food Safety Standard –
Determination of Lead in Foods
1 Application Scope
This Standard specifies graphite furnace atomic absorbance spectrometry, inductively
coupled plasma mass spectrometry, flame atomic absorbance spectrometry, dithizone
colorimetry for the determination of lead in foods.
This Standard applies to the determination of lead all kinds of foods.
Method I – Graphite Furnace Atomic Absorbance Spectrometry
2 Principle
Treat test specimen by digestion; carry out graphite furnace atomization; measure
absorbance value at 283.3 nm. Lead absorbance value is in direct proportion to lead
content within a certain concentration range; it is compared with standard series for
quantification.
3 Reagents and Materials
Unless specified otherwise, all reagents used for this method are guaranteed reagents
and the water is water grade II specified in GB/T 6682.
3.1 Reagents
3.1.1 Nitric acid (HNO3).
3.1.2 Perchloric acid (HClO4).
3.1.3 Ammonium dihydrogen phosphate (NH4H2PO4).
3.1.4 Palladium nitrate [Pd(NO3)2].
3.2 Preparation of reagents
3.2.1 Nitric acid solution (5 + 95). measure 50 mL of nitric acid; add to 950 L of water;
mix up.
3.2.2 Nitric acid solution (1 + 9). measure 50 mL of nitric acid; add to 450 L of water;
mix up.
3.2.3 Ammonium dihydrogen phosphate-palladium nitrate solution. weigh 0.020 g of
palladium nitrate; add a small amount of nitric acid solution (1 + 9) to dissolve; then
add 2.0 g of ammonium dihydrogen phosphate; use nitric acid solution (5 + 95) to dilute
to 100 mL after dissolving; mix up.
3.3 Standard substance
Lead nitrate [Pb(NO3)2, CAS no.. 10099-74-8]. purity > 99.99% or the lead standard
solution of a certain concentration which has been certified by a national certification
institution and awarded the certificate of standard substance.
3.4 Preparation of standard solutions
3.4.1 Lead standard stock solution (1 000 mg/L). weigh accurately 1.598 5 g
(accurate to 0.000 1 g); use a small amount of nitric acid solution (1 + 9) to dissolve;
transfer to a 1000 mL volumetric flask; add water to graduate and mix up.
3.4.2 Lead standard intermediate solution (1.00 mg/L). absorb 1.00 mL of lead
standard stock solution (1 000 mg/L) to pour into a 1 000 mL volumetric flask; add nitric
acid solution (5 + 95) to graduate; mix up.
3.4.3 Lead standard serial solution. absorb respectively 0 mL, 0.500 mL, 1.00 mL,
2.00 mL, 3.00 mL and 4.00 mL of lead standard intermediate solution (1.00 mg/L) to
pour into a 100 mL volumetric flask; add nitric acid solution (5 + 95) to graduate; mix
up. Then the mass concentrations of lead standard serial solution are respectively 0
μg/L, 5.00 μg/L, 10.0 μg/L, 20.0 μg/L, 30.0 μg/L and 40.0 μg/L.
NOTE The mass concentrations of lead in the standard solution series can be decided in
accordance with the sensitivity of instrument and the actual lead content in test specimen.
4 Apparatus
NOTE All glass wares and PTFE digestion inner tanks shall be soaked in nitric acid (1 + 5)
overnight, washed with tap water repeatedly and washed clean in the end.
4.1 Atomic absorbance spectrometer. equipped with graphite furnace atomizer and
attached with lead hollow cathode lamp.
4.2 Analytical balance. sensitivities 0.1 mg and 1 mg.
4.3 Adjustable electric furnace.
4.4 Adjustable electric hot plate.
4.5 Microwave digestion system. equipped with PTFE digestion inner tank.
4.6 Constant temperature drying oven.
4.7 Pressure digestion tank. equipped with PTFE digestion inner tank.
m – test specimen weight or transferring volume, in g or mL;
1 000 – conversion coefficient.
When lead content ≥ 1.00 mg/kg (or mg/L), the calculation results are rounded off to 3
significant digits; when lead content < 1.00 mg/kg (or mg/L), the calculation results are
rounded off to 2 significant digits.
7 Accuracy
The absolute difference between the results obtained from two independent
determinations under repeatable conditions shall not exceed 20% of the arithmetic
mean value.
8 Others
When the weight of test specimen is 0.5 g (or 0.5 mL) and the constant volume is 10
mL, the method detection limit 0.02 mg/kg (or 0.02 mg/L) and the quantification limit
0.04 mg/kg (or 0.04 mg/L).
Method II – Inductively Coupled Plasma Mass Spectrometry
See GB 5009.268.
Method III – Flame Atomic Absorption Spectrometry
9 Principle
After the treatment of test specimen, lead ion and sodium diethyl dithiocarbamate
(DDTC) forms a complex under certain pH conditions; it is lead to an atomic absorption
spectrometer after extraction separation with 4-methyl-2-pentanone (MIBK).
Absorbance is measured at 283.3 nm ...
......
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.