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GB 5009.138-2017 English PDF (GB5009.138-2017)

GB 5009.138-2017 English PDF (GB5009.138-2017)

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GB 5009.138-2017: Food safety national standard -- Determination of nickel in food

This Standard specifies using the graphite furnace atomic absorption spectrometry to determine the nickel content in the food. This Standard is applicable to determine the nickel content in various foods.
GB 5009.138-2017
GB
NATIONAL STANDARD OF THE
PEOPLE REPUBLIC OF CHINA
National Food Safety Standard
?€? Determination of Nickel in Food
ISSUED ON. APRIL 06, 2017
IMPLEMENTED ON. SEPTEMBER 17, 2017
Issued by. National Health and Family Planning Commission of PRC.;
China Food and Drug Administration.
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Principle ... 4
3 Reagents and Materials ... 4
4 Instrument and Equipment ... 5
5 Analytical Procedures ... 6
6 Expression of Analytical Results ... 8
7 Precision ... 8
8 Others ... 8
Appendix A Recommended Temperature-Rise Procedures for Microwave
Digestion ... 9
Appendix B Recommended Temperature-Rise Procedures for Graphite
Furnace ... 10
National Food Safety Standard
?€? Determination of Nickel in Food
1 Scope
This Standard specifies using the graphite furnace atomic absorption spectrometry to determine the nickel content in the food.
This Standard is applicable to determine the nickel content in various foods. 2 Principle
After the digestion of the sample, measure the absorbance at 232.0nm through the atomization of the graphite furnace. In a certain concentration range, the nickel absorbance value is proportional to the nickel content; quantify through the comparison with the standard series.
3 Reagents and Materials
Unless otherwise specified, the reagents used in this method are guaranteed reagents; while water is Class-II water specified in GB/T 6682.
3.1 Reagents
3.1.1 Nitric acid (HNO3).
3.1.2 Perchloric acid (HClO4).
3.1.3 Palladium nitrate [Pd(NO3)2].
3.1.4 Ammonium dihydrogen phosphate (NH4H2PO4).
3.2 Reagents preparation
3.2.1 Nitric acid solution (0.5mol/L). pipette 3.2mL of nitric acid; add water to dilute to 100mL, mix evenly.
3.2.2 Nitric acid solution (1+1). weigh 500mL of nitric acid; mix with 500mL of water evenly.
3.2.3 Ammonium dihydrogen phosphate ?€? palladium nitrate solution. take 0.02g of palladium nitrate; add small amount of nitric acid solution (1+1) by several times to 4.8 Muffle furnace.
5 Analytical Procedures
5.1 Specimen preparation
NOTE. during the sampling and specimen preparation period, the specimen contamination shall be avoided.
5.1.1 Grains and beans samples
After removing the debris, crush the samples and store into the plastic bottles. 5.1.2 Vegetables, fruits, fish, meat and the like samples
Wash the samples with water, dry them; then take the edible part, and make into the homogenate state, and store into the plastic bottles.
5.1.3 Drinks, wine, vinegar, soy sauce, edible vegetable oil, liquid milk and other liquid samples
Shake the samples evenly.
5.2 Specimen digestion
5.2.1 Wet digestion
Take 0.2g~3g (accurate to 0.001g) of solid specimen or accurately pipette 0.500mL~5.00mL of liquid specimen into the digestion tube with scale; add 10mL of nitric acid, 0.5mL of perchloric acid; digest on the adjustable electric hot furnace (reference condition. 120??C/0.5h~1h, rise to 180??C/2h~4h, rise to 200??C~220??C). If the digestive juice is tan, add small amount of nitric acid and digest till white smoke appears; then digestive juice is colorless and transparent or slightly yellow; take out the digestion tube; after cooling off, use water to make constant volume to 10mL, mix evenly and for later-use. Meanwhile do the blank test of the reagent. The conical flask can also be used; perform the wet digestion on the adjustable electric hot plate according to the above-mentioned method.
5.2.2 Microwave digestion
Take 0.2g~0.8g (accurate to 0.001g) of solid specimen or accurately pipette 0.500mL~3.00mL of liquid specimen into the microwave digestion tank; add 5mL of nitric acid; digest the specimen according to the microwave digestion procedures; the digestion condition can refer to Appendix A. After cooling off, take out the digestion tank; expel acid on the electric hot plate at 140??C~160??C to 1mL or so. After the digestion tank is cooling off, transfer the digestive juice into the 10mL volumetric flask; use small amount of water to wash and digest the tank for twice and three times; combine the washing liquids into the volumetric flask; use water to make constant volume to the scale; mix evenly for later-use. Meanwhile do the blank test of the reagent.
5.2.3 Pressure tank digestion
Take 0.2g~1g (accurate to 0.001g) of solid specimen or accurately pipette 0.500mL~5.00mL of liquid specimen into the digestion inner tank; add 5mL of nitric acid. Cover the inner cap, tighten the stainless-steel jacket; put into the constant temperature oven; maintain for 4h~5h at 140??C~160??C. After cooling, slowly loosen the outer tank; take out the digestion inner tank; expel acid on the adjustable electric hot plate at 140??C~160??C to 1mL or so. After cooling off, transfer the digestive juice into the 10mL volumetric flask; use small amount of water to wash the inner tank and inner cap for twice ~ three times; combine the washing liquids into the volumetric flask, use water to make constant volume to the scale. Meanwhile do the blank test of the reagent.
5.2.4 Dry ashing
Take 0.5g~5g (accurate to 0.001g) of solid specimen or accurately pipette 0.500mL~10.0mL of liquid specimen into a crucible; heat with small fire and carbonize to smokeless; transfer into the muffle furnace to ash for 3h~4h at 550??C. After cooling off, take out; for the specimen that is not ashed completely, add several drops of nitric acid; heat on small fire; carefully dry it; then transfer into the 550??C muffle furnace; continue to ash for 1h~2h till the specimen becomes the white ash state; cooling off, take out; dissolve by appropriate amount of nitric acid solution (1+1); then use water to make constant volume to 10mL. Meanwhile do the blank test of the reagent. 5.3 Determination
5.3.1 Instrument reference conditions
Adjust the instrument to the optical state according to its performance. The reference condition can refer to Appendix B.
5.3.2 Drawing of standard curve
Inject 10??L of nickel standard series solution and 5??L of ammonium dihydrogen phosphate-palladium nitrate solution (the optical sample injection volume can be determined according to the used instrument) into the graphite furnace at the same time according to the order of mass concentration from low to high; after atomization, measure the absorbance value; then draw the standard curve with mass concentration as abscissa, and absorbance value as the ordinate.
5.3.3 Determination of specimen solution

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