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GB 5009.267-2016 English PDF (GB5009.267-2016)

GB 5009.267-2016 English PDF (GB5009.267-2016)

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GB 5009.267-2016: National Food Safety Standard -- Determination of Iodine in Foods

This Standard specifies the methods for the determination of iodine in foods. Method I, the oxidation-reduction titration method, applies to the determination of iodine in kelp, laver, wakame and other algae and their products. Method II, the As-Ce catalytic spectrophotometric method, applies to the determination of iodine in grains, vegetables, fruits, beans and their products, milk and milk products, meats, fish, eggs and other foods. Method III, the gas chromatographic method, applies to the determination of iodine in foods for infants and young children and milk products.
GB 5009.267-2016
GB
NATIONAL STANDARD OF THE
PEOPLE REPUBLIC OF CHINA
National Food Safety Standard ?€?
Determination of Iodine in Foods
ISSUED ON. DECEMBER 23, 2016
IMPLEMENTED ON. JUNE 23, 2017
Issued by. National Health and Family Planning Commission of the
PEOPLE Republic of China;
China Food and Drug Administration.
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Table of Contents
Foreword ... 4
1 Application Scope ... 5
Method I Oxidation-reduction Titration Method ... 5
2 Principle ... 5
3 Reagents and Materials ... 5
4 Apparatus ... 7
5 Analytical Procedure ... 7
6 Expression of Analytical Results ... 8
7 Accuracy ... 9
8 Others ... 9
Method II As(III)-Ce4+ Catalytic Spectrophotometric Method ... 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
Method III Gas Chromatographic Method ... 13
16 Principle ... 13
17 Reagents and Materials ... 13
18 Apparatus ... 14
19 Analytical Procedure ... 15
20 Expression of Analytical Results ... 16
21 Accuracy ... 17
22 Others ... 17
Annex A Gas Chromatogram of Iodine Standard Derivative ... 18
Foreword
This Standard replaces GB 5413.23-2010, National Food Safety Standard
Determination of Iodine in Foods for Infants and Young Children, Milk and Milk Products, SC/T 3010-2001, Determination of Iodine in Kelp, and WS 302-2008, Method for Determination of Iodine in Foodstuff by As(III)-Ce4+ Catalytic Spectrophotometry.
Compared with the standards above, the major changes of this Standard are as follows. -- it changes the standard name into ?€?National Food Safety Standard ?€?
Determination of Iodine in Food?€?;
-- it modifies the methods for specimen preparation and pretreatment of the oxidation-reduction titration method;
-- it adds the detection limits for the oxidation-reduction titration method. National Food Safety Standard ?€?
Determination of Iodine in Food
1 Application Scope
This Standard specifies the methods for the determination of iodine in foods. Method I, the oxidation-reduction titration method, applies to the determination of iodine in kelp, laver, wakame and other algae and their products.
Method II, the As-Ce catalytic spectrophotometric method, applies to the determination of iodine in grains, vegetables, fruits, beans and their products, milk and milk products, meats, fish, eggs and other foods.
Method III, the gas chromatographic method, applies to the determination of iodine in foods for infants and young children and milk products.
Method I Oxidation-reduction Titration Method
2 Principle
After carbonization and ashing of specimen, organic iodine is converted into inorganic iodide ions; in an acid medium, bromine water is used to oxidize iodide ions into iodate ions; the iodate ions generated is reduced in the acid solution of potassium iodide to separate iodine out; sodium thiosulfate solution is used to titrate the iodine separated out in the reaction.
3 Reagents and Materials
Unless specified otherwise, all reagents used for this method are analytically pure and the water is of grade 3 water specified in GB/T 6682.
3.1 Reagents
3.1.1 Anhydrous sodium carbonate (Na2CO3).
3.1.2 Liquid bromine (Br2).
4 Apparatus
4.1 Laboratory blender.
4.2 High-speed pulverizer.
4.3 Analytical balance. sensitivity 0.1 mg.
4.4 Electric thermostatic drying oven.
4.5 Muffle furnace. ??? 600??C.
4.6 Porcelain crucible. 50 mL.
4.7 Adjustable electric furnace. 1 000 W.
4.8 Iodine flask. 250 mL.
4.9 Brown acid burette. 25 mL, minimum scale 0.1 mL.
4.10 Acid microburette. 1 mL, minimum scale 0.01 mL.
5 Analytical Procedure
5.1 Specimen preparation
5.1.1 Dry specimen is crushed by a high-speed pulverizer, passes through a standard sieve of mesh size 425 ??m and is stored in a dark place or at low temperature. 5.1.2 Take the homogenate of the edible part of fresh and frozen specimen, and then refrigerate it in a closed space or freeze it in storage.
5.1.3 For the liquid specimens such as concentrated algae juice and algae beverage, take specimen after blending.
5.2 Specimen analysis
5.2.1 Weigh 2 g ~ 5 g (accurate to 0.1 mg) of specimen to place into a 50-mL porcelain crucible; add 5 mL ~ 10 mL of sodium carbonate solution to soak specimen completely; allow to stand for 5 min; place in an electric thermostatic drying oven for drying for 3 h at 101??C ~ 105??C; take specimen out after it is dried.
5.2.2 Use an electric furnace to heat in a fume hood to ensure that specimen is fully carbonized until smokeless; place in muffle furnace to burn for 40 min at 550??C ?? 25??C; cool to about 200??C; take out. Add a small amount of water in a crucible for grinding; transfer all solution and residual to a 250-mL beaker; use water to wash the crucible for several times and incorporate into the beaker to make the volume of solution in the beaker is 150 mL ~ 200 mL; boil for 5 min.
10.1.4 Sulphuric acid (H2SO4). guaranteed reagent.
10.1.5 Sodium hydroxide (NaOH).
10.1.6 Arsenic trioxide (As2O3).
10.1.7 Sodium chloride (NaCl). guaranteed reagent.
10.1.8 Ammonium ceric sulphate [(Ce(NH4)4(SO4)4??2H2O) or Ce(NH4)4(SO4)4??4H2O]. 10.2 Preparation of reagents
10.2.1 Potassium carbonate-sodium chloride mixed solution. weigh 30 g of anhydrous potassium carbonate and 5 g of sodium chloride to dissolve in 100 mL of water. It can be stored for 6 months at room temperature.
10.2.2 Zinc sulphate-potassium chlorate mixed solution. weigh 5 g of potassium chlorate to place into a beaker; add 100 mL of water; heat to dissolve; add 10 g of zinc sulphate; stir to dissolve. It can be stored for 6 months at room temperature. 10.2.3 Sulphuric acid solution (2.5 mol/L). measure 140 mL of sulphuric acid to pour slowly into a beaker containing 700 mL of water; keep stirring; cool to room temperature; use water to dilute to 1 000 mL; mix up.
10.2.4 Arsenious acid solution (0.054 mol/L). weigh 5.3 g of arsenic trioxide, 12.5 g of sodium chloride and 2.0 g of sodium chloride to place into a 1-L beaker; add about 500 mL of water; heat to fully dissolve before cooling to room temperature; add slowly 400 mL of 2.5 mol/L sulphuric acid; cool to room temperature before using water to dilute to 1 L; store in a brown bottle. It can be stored for 6 months at room temperature. (arsenic trioxide and arsenious acid solution prepared are highly toxic, so the operating specifications regarding highly toxic substances shall be followed.)
10.2.5 Ammonium ceric sulphate solution (0.015 mol/L). weigh 9.5 g of ammonium ceric sulphate [Ce(NH4)4(SO4)4??2H2O] or 10 g of [Ce(NH4)4(SO4)4??4H2O]; dissolve in 500 mL of 2.5 mol/L sulphuric acid; use water to dilute to 1 L; store in a brown bottle. It can be stored for 3 months in a dark place at room temperature.
10.2.6 Sodium hydroxide solution (2 g/L). weigh 4.0 g of sodium hydroxide to dissolve in 2 000 mL of water.
10.3 Standard substance
Potassium iodide (KI). guaranteed reagent.
10.4 Preparation of iodine standard solutions
10.4.1 Iodine standard stock solution (100 ??g/mL). weigh accurately 0.130 8 g of potassium iodide (dried in silica gel drier for 24 h) to place into a 500-mL beaker; use sodium hydroxide to dissolve before transferring all to a 1 000-mL volumetric flask; add 12.1.5 If the iodine content of wet specimen needs to be converted into that of dry specimen, the moisture content in food shall be determined as ...

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