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GB 5009.17-2014 English PDF (GB5009.17-2014)

GB 5009.17-2014 English PDF (GB5009.17-2014)

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GB 5009.17-2014: National Food Safety Standard -- Determination of total mercury and organic-mercury in food

The first chapter of this Standard specified the determination method for total mercury in foods. The first chapter of this Standard is applicable to the determination of total mercury in foods.
GB 5009.17-2014
GB
NATIONAL STANDARD OF
THE PEOPLE REPUBLIC OF CHINA
National Food Safety Standard-Determination of total
mercury and organic-mercury in foods
ISSUED ON. SEPTEMBER 21, 2015
IMPLEMENTED ON. MARCH 21, 2016
Issued by. National Health and Family Planning Commission
Table of Contents
Foreword ... 4
1 Scope ... 5
Chapter I Determination of total mercury in foods ... 5
The first method Atomic fluorescence spectrometry ... 5
2 Principle... 5
3 Reagents and materials ... 5
4 Apparatus ... 7
5 Analysis procedures ... 7
6 Representation of analysis result ... 10
7 Precision... 10
8 Other ... 10
The second Method Cold Atomic Absorption Spectrometric Method ... 11
9 Principle... 11
10 Reagents and materials... 11
11 Apparatus ... 12
12 Analysis procedures ... 13
13 Representation of analysis result ... 14
14 Precision ... 14
15 Other ... 15
Chapter II Determination of methylmercury in foods ... 15
Liquid chromatography - atomic fluorescence spectrometry method ... 15 16 Principle... 15
17 Reagents and materials... 15
18 Apparatus ... 17
19 Analysis procedures ... 17
13 Representation of analysis result ... 19
21 Precision ... 20
22 Other ... 20
Annex A ... 21
Annex B ... 22
Foreword
This Standard replaces GB/T 5009.17-2003 Determination of Total Mercury and Organic-mercury in Foods.
Compared with GB/T 5009.17-2003, the main changes are as follows.
- modified the standard name to ?€?National Food Safety Standard-
Determination of total mercury and organic-mercury in foods?€?;
- deleted double sulphur hydrazone colorimetry method for determination of total mercury, gas chromatography for determination of organic mercury and atomic absorption spectrometry;
- added liquid chromatography - atomic fluorescence spectrometry (LC-
AFS) for determination of methylmercury.
National Food Safety Standard - Determination of total
mercury and organic-mercury in foods
1 Scope
The first chapter of this Standard specified the determination method for total mercury in foods.
The first chapter of this Standard is applicable to the determination of total mercury in foods.
The second chapter of this Standard specifies the liquid chromatography - atomic fluorescence spectrometry for determination of methylmercury in foods. The second chapter of this Standard is applicable to the determination of methylmercury in foods.
Chapter I Determination of total mercury in foods
The first method Atomic fluorescence spectrometry
2 Principle
After the sample is heated and digested by acid, in acidic medium, mercury in sample is reduced to atomic mercury by potassium borohydride or sodium
borohydride. It is brought by carrier gas (argon) into the atomizer. Under irradiation of mercury hollow cathode lamp, ground state mercury atom is stimulated to high energy state. When it is back from high energy state to ground state, it shall emit the characteristic wavelength fluorescence. Its fluorescence intensity is proportional to the mercury content, in quantitative comparison with the standard series solution.
3 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.
3.1 Reagents
3.1.1 Nitric acid (HNO3).
3.1.2 Hydrogen peroxide (H2O2).
3.1.3 Sulfuric acid (H2SO4).
3.1.4 Potassium hydroxide (KOH).
3.1.5 Potassium borohydride (KBH4). analytically pure.
3.2 Reagent preparation
3.2.1 Nitric acid solution (1+9). measure 50 mL of nitric acid; slowly add it into 450 mL of water.
3.2.2 Nitric acid solution (95+5). measure 5 mL of nitric acid; slowly add it into 95 mL of water.
3.2.3 Potassium hydroxide solution (5g/L). weigh 5.0 g of potassium
hydroxide; dissolve it in pure water; set volume to 1000 mL; well mix it. 3.2.4 Solution of potassium borohydride (5g/L). weigh 5.0 g of potassium borohydride; use 5g/L potassium hydroxide solution to dissolve and set volume to 1000 mL; well mix it; prepare it when required.
3.2.5 Potassium dichromate nitric acid solution (0.5 g/L). weigh 0.05 g of potassium dichromate to dissolve in 100 mL of nitric acid solution (5+95). 3.2.6 Nitric acid-perchloric acid mixed solution (5+1). measure 500 mL of nitrate and 100 mL of perchloric acid; well mix.
3.3 Standard product
Mercuric chloride (HgCl2). purity ??? 99%.
3.4 Preparation of standard solution
3.4.1 Mercury standard stock solution (1.00 mg/mL). accurately weigh 0.1354 g of dried mercuric chloride; use potassium dichromate nitric acid solution (0.5 g/L) to dissolve and transfer to 100 mL measuring flask; dilute it to scale; well mix; the concentration of this solution is 1.00 mg/mL; store it in 4??C refrigerator in dark conditions; it can be stored for 2 years; or purchase the standard solution substance awarded by national certification standard certificate.
3.4.2 Mercury standard intermediate solution (10 ??g/mL). pipette 1.00 mL of mercury standard solution (1.00 mg/mL) in 100 mL measuring flask; use
potassium dichromate nitric acid solution (0.5 g/L) to dilute to scale; well mix; sample OR pipette 1 mL ~ 5 mL of liquid sample (accurate to 0.001 g) into digestion inner tank. Add 5 mL of nitrate to soak overnight. Cover the inner lid. Tighten the stainless steel jacket. Place into thermostatic oven for 4h ~ 5h at 140??C ~ 160??C. Naturally cool it to room temperature in the oven. Then slowly loosen the stainless steel jacket. Take it from the digestion inner tank. Use few amount of water to clean the inner lid. Place on temperature control heating plate or ultrasonic water bath. Drive away brown gas at 80??C or by 2 min ~ 5 min of ultrasonic degassing. Take the digestion inner tank out. Transfer the digestive fluid to 25 mL flask. Use few amount of water to clean the inner tank for 3 times. Combine the detergent in the flask and set volume to scale. Well mix for use. Conduct the blank test at the same time.
5.2.2 Microwave digestion method
Weigh 0.2 g ~ 0.5 g (accurate to 0.001 g) of solid sample, 0.2 g ~ 0.8 g of fresh sample OR pipette 1 mL ~ 3 mL of liquid sample into digestion inner tank. Add 5 mL ~ 8 mL of nitrate. Cover and place for overnight. Tighten the lid. Digest according to the standard operation procedures of microwave digestion system (see Table A.1 of Annex A for digestion reference conditions). Take it out after cooling. Slowly open the tank to exhaust. Use few amount of water to clean the inner lid. Place on temperature control heating plate or ultrasonic water bath. Drive away brown gas at 80??C or by 2 min ~ 5 min of ultrasonic degassing. Take the digestion inner tank out. Transfer the digestive fluid to 25 mL plastic flask. Use few amount of water to clean the inner tank for 3 times. Combine the detergent in the flask and set volume to scale. Well mix for use. Conduct the blank test at the same time.
5.2.3 Reflux digestion method
5.2.3.1 Grain
Weigh 1.0 g ~ 4.0 g (accurate to 0.001 g) of sample. Place it in digestion Erlenmeyer flask. Add few glass beads. Add 45 mL of nitric acid, 10 mL of sulfuric acid. Rotate the Erlenmeyer flask to prevent partial carbonization. After mounting condenser tube, low heat it when it starts bubbling. After bubbling stops, heat it for 2h. If during heating, the solution turns brown, it shall add 5 mL of nitrate. Add 5 mL of nitrate, and continue refluxing for 2h till the sample is dissolved by digestion. Generally, it appears light yellow or colorless. After ...

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