GB/T 13081-2022 PDF English
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| GB/T 13081-2022 | English | 140 |
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Determination of mercury in feeds
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| GB/T 13081-2006 | English | 70 |
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Determination of mercury in feeds
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| GB/T 13081-1991 | English | 199 |
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Method for determination of mercury in feeds
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GB
NATIONAL STANDARD OF THE
PEOPLE'S REPUBLIC OF CHINA
ICS 65.120
CCS B 46
Replacing GB/T 13081-2006
Determination of mercury in feeds
Issued on. DECEMBER 30, 2022
Implemented on. JULY 1, 2023
Issued by. State Administration for Market Regulation;
Standardization Administration of PRC.
Table of Contents
Foreword... 3
1 Scope... 5
2 Normative references... 5
3 Terms and definitions... 5
4 Atomic fluorescence spectrometry (arbitration method)... 5
5 Cold atomic absorption spectrometry... 10
6 Direct injection method... 13
Foreword
This document was drafted in accordance with the provisions of GB/T 1.1-2020
Directives for standardization - Part 1.Rules for the structure and drafting of
standardizing documents.
This document replaces GB/T 13081-2006 Determination of mercury in feeds.
Compared with GB/T 13081-2006, in addition to structural adjustments and editorial
changes, the main technical changes are as follows.
a) The scope of application has been increased to concentrate supplements and
feed ingredients; the quantitation limits of atomic fluorescence spectrometry
and cold atomic absorption spectrometry are added (see Chapter 1; see Chapter
1 of the 2006 edition);
b) The treatment methods of high-pressure tank digestion and microwave
digestion are changed (see 4.5.1.1 and 4.5.1.2; see 4.4.1.1 and 4.4.1.2 of the
2006 edition);
c) The reference conditions of microwave digestion are changed (see 4.5.1.2; see
4.4.1.2 of the 2006 edition);
d) The reference conditions of the atomic fluorescence spectrometry instrument
are changed (see 4.5.2; see 4.4.3 of the 2006 edition);
e) The test data processing is changed (see 4.6 and 5.6; see 4.5 and 5.5 of the
2006 version);
f) The expression of precision is changed (see 4.7 and 5.7; see 4.5.3 and 5.5.3 of
the 2006 edition);
g) The direct injection method is added (see Chapter 6).
Please note that some content in this document may be subject to patents. The publisher
of this document assumes no responsibility for identifying patents.
This document was proposed by and is under the jurisdiction of the National Technical
Committee on Feed Industry of Standardization Administration of China (SAC/TC76).
This document was drafted by Sichuan Provincial Feed Work Station.
Main drafters of this document. Zhao Lijun, Chen Fei, Li Yun, Zhao Jianzhong, Zhang
Jing, Yue Qin, Wang Yuping, Feng Bo, Gao Qingjun, Li Li, Lin Shunquan, Cheng
Chuanmin, Chen Hong, Liao Feng.
The previous versions of this document and the documents it replaces are as follows.
-- It was first released as GB 13081-1991 in 1991; it was adjusted to a
recommended national standard in 1997, numbered to GB/T 13081-1991, and
revised for the first time in 2006;
-- This is the second revision.
Determination of mercury in feeds
1 Scope
This document describes the atomic fluorescence spectrometry, cold atomic absorption
spectrometry, and direct injection methods for the determination of total mercury in
feeds.
This document is applicable to the determination of total mercury in compound feeds,
concentrated feeds, concentrate supplements, additive premixed feeds, feed raw
materials, and feed additives.
Atomic fluorescence spectrometry. When the sample weight is 0.5 g and the constant
volume is 50 mL, the method detection limit is 0.6 μg/kg and the quantification limit is
3 μg/kg. Cold atomic absorption spectrometry. When the sample weight is 2 g and the
constant volume is 100 mL, the method detection limit is 3 μg/kg and the quantitation
limit is 10 μg/kg. Direct injection method. When the sample weighing amount is 0.1 g,
the detection limit of the method is 0.3 μg/kg, and the quantification limit is 1 μg/kg.
2 Normative references
The contents of the following documents constitute essential provisions of this
document through normative references in the text. For the dated referenced documents,
only the versions with the indicated dates are applicable to this document; for the
undated referenced documents, only the latest version (including all the amendments)
is applicable to this document.
GB/T 6682 Water for analytical laboratory use - Specification and test methods
GB/T 20195 Animal feeding stuffs - Preparation of test samples
3 Terms and definitions
There are no terms or definitions that need to be defined in this document.
4 Atomic fluorescence spectrometry (arbitration method)
4.1 Principle
After the sample is digested by acid heating, mercury is reduced to atomic mercury by
potassium borohydride (KBH4) in the acidic medium, which is brought into the
atomizer by argon gas. Under the irradiation of a special mercury hollow cathode lamp,
the ground-state mercury atoms are excited to a high energy state and then deactivated
back to the ground state, which emit fluorescence with a characteristic wavelength. Its
fluorescence intensity is proportional to the mercury content and can be quantified by
the external standard method.
4.2 Reagents or materials
WARNING -- Mercury is highly toxic. Pay attention to ventilation when handling
and avoid contact with skin and clothing. All kinds of strong acids shall be handled
carefully and shall be handled in a fume hood.
4.3 Instruments and equipment
4.3.1 Atomic fluorescence spectrometer. It is equipped with a mercury hollow cathode
lamp.
4.3.2 Analytical balance. The sensitivity is 0.0001 g.
4.3.3 High-pressure digestion tank. It is equipped with a 100 mL
polytetrafluoroethylene digestion tube.
4.3.4 Microwave digestion instrument. It is equipped with a 50 mL
polytetrafluoroethylene digestion tube.
4.3.5 Constant temperature drying oven. The temperature control accuracy is ±2 °C.
4.3.6 Ultrasonic cleaner.
NOTE. Glassware and polytetrafluoroethylene digestion tubes need to be soaked in nitric acid solution
I (4.2.4) for 24 hours, and then rinsed repeatedly with water.
4.4 Samples
The sample is prepared according to GB/T 20195.The solid sample shall be at least 200
g. It is crushed so that it all passes through an analysis sieve with a pore size of 0.425
mm; it is mixed thoroughly and stored in an airtight container for later use.
4.5 Test procedures
4.5.1 Sample solution preparation
4.5.3 Determination
Adjust the atomic fluorescence spectrometer to the best working condition and start
measurement after stabilizing for 10 to 20 minutes. Use nitric acid solution III (4.2.6)
as the carrier fluid and potassium borohydride solution (4.2.8) as the reducing agent,
and use nitric acid solution II (4.2.5) to continuously inject samples; after the reading
is stable, measure the standard series of solutions.
4.6 Test data processing
The mercury content w in the sample is expressed as a mass fraction, in milligrams per
kilogram (mg/kg), and is calculated according to formula (1).
4.7 Precision
Under repeatability conditions, the ratio of the absolute difference between the two
independent measurement results and their arithmetic mean to the arithmetic mean, that
is, the relative deviation r, shall meet the requirements of Table 3.
5 Cold atomic absorption spectrometry
5.1 Principle
The sample is digested with nitric acid-sulfuric acid, and the mercury is converted into
an ionic state. Under strong acid conditions, mercury ions are reduced to elemental
mercury by stannous chloride, which is blown out by dry clean air. The absorbance is
measured at a wavelength of 253.7 nm and quantified by the external standard method.
5.2 Reagents or materials
WARNING -- Mercury is highly toxic. Pay attention to ventilation when handling
and avoid contact with skin and clothing. All kinds of strong acids shall be handled
carefully and shall be handled in a fume hood.
Unless otherwise specified, use only guaranteed reagents.
5.2.1 Water. The second-grade water specified in GB/T 6682.
5.2.2 Nitric acid.
5.2.3 Sulfuric acid.
5.2.9 Mercury standard working solution (0.1 μg/mL). Accurately pipette 1 mL of
mercury standard intermediate solution (5.2.8), place it in a 100 mL volumetric flask,
add the mixed acid solution (5.2.6) to dilute to the mark, and mix well. Prepare it fresh
just before use.
5.3 Instruments and equipment
5.3.1 Cold atom mercury analyzer. It is equipped with a 50 mL reducing bottle.
5.3.2 Analytical balance. The sensitivity is 0.0001 g.
5.5 Test procedures
5.5.1 Preparation of sample solution
Do two experiments in parallel. Weigh 1 g~5 g of the sample, accurate to 0.0001 g,
place it in a 250 mL Erlenmeyer flask, add a few glass beads, add 25 mL of nitric acid
(5.2.2) and 5 mL of sulfuric acid (5.2.3), and rotate the Erlenmeyer flask to prevent
local carbonization. Install the condenser tube, heat over low heat, and stop heating
when foaming begins. After foaming stops, reheat and reflux for 2 hours.
5.5.2 Standard curve drawing
Accurately pipette 0 mL, 0.10 mL, 0.20 mL, 0.30 mL, 0.40 mL, and 0.50 mL of mercury
standard working solution (5.2.9), which is equivalent to 0 μg, 0.01 μg, 0.02 μg, 0.03
μg, 0.04 μg, and 0.05 μg of mercury. Place them in the reduction bottles, add 10 mL of
mixed acid solution (5.2.6) each, and then add 2 mL of stannous chloride solution
(5.2.5); immediately close the reduction bottles tightly and react for 2 minutes; record
the maximum absorbance of the cold atom mercury analyzer. Draw a standard curve
with absorbance as the ordinate and mercury concentration as the abscissa.
5.6 Test data processing
The mercury content w in the sample is expressed as a mass fraction, in milligrams per
kilogram (mg/kg), and is calculated according to formula (2).
6 Direct injection method
6.1 Principle
After the sample is dried at high temperature and catalytically pyrolyzed, the mercury
is reduced to elemental mercury, which is enriched with gold amalgam or directly
brought into the detector through a carrier gas, and the atomic absorption signal of
mercury is measured at a wavelength of 253.7 nm, or the atomic fluorescence signal of
mercury is detected with excitation by a mercury lamp; it is quantified by external
standard method.
6.2 Reagents or materials
WARNING -- Mercury is highly toxic. Pay attention to ventilation when handling
and avoid contact with skin and clothing. All kinds of strong acids shall be handled
carefully and shall be handled in a fume hood.
Unless otherwise specified, use only guaranteed reagents.
6.3 Instruments and equipment
6.3.1 Direct injection mercury analyzer.
6.3.2 Analytical balance. The sensitivity is 0.0001 g.
6.3.3 Muffle furnace. The temperature control accuracy is ±20 ℃.
6.3.4 Sample boat. It is made of nickel or quartz, burned in a muffle furnace at
550 ℃±20 ℃ for 1 hour before use, taken out and placed in a desiccator to cool for
later use.
6.5 Test procedures
6.5.1 Standard curve drawing
Accurately pipette 0.1 mL of the low-concentration standard series solutions (6.2.7) and
the high-concentration standard series solutions (6.2.8) respectively into the sample
boats. The mercury masses of the low-concentration standard series solutions are 0 ng,
0.5 ng, 1.0 ng, 2.0 ng, 5.0 ng, 10.0 ng, and 20.0 ng; the mercury masses of the high-
concentration standard series solutions are 30.0 ng, 60.0 ng, 80.0 ng, 100 ng, 300 ng,
and 500 ng.
6.5.2 Determination
Weigh 0.05 g~0.2 g of the sample (accurate to 0.0001 g) into the sample boat, measure
on the machine, and calculate the mercury content in the sample according to the
standard curve. Do a blank test at the same time.
6.5.3 Instrument reference conditions
The reference conditions for the direct injection mercury analyzer are shown in Table 4
and Table 5.
6.6 Test data processing
The mercury content w in the sample is expressed as a mass fraction, in milligrams per
kilogram (mg/kg), and is calculated according to formula (3).
......
Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al.
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