GB/T 25222-2010 Grain and Oil Inspection Determination of Phosphate Residues in Grains Spectrophotometric Method GB/T25222-2010 Standard download decompression password: www.bzxz.net
This standard specifies the terms and definitions, principles, reagents and materials, instruments and equipment, sampling, sample preparation, operating procedures, result calculation and expression for the determination of phosphide residues in grains by spectrophotometry. This standard is applicable to the determination of phosphide fumigant residues in grains. The detection limit of this standard method is 0.01mg/kg.
This standard is proposed by the State Administration of Grain.
This standard is under the jurisdiction of the National Technical Committee for Grain and Oil Standardization.
The responsible drafting unit of this standard: Nanjing University of Finance and Economics.
Participating drafting units of this standard: Jiangsu Grain and Oil Quality Supervision and Inspection Institute, Nanjing Grain and Oil Quality Supervision and Inspection Institute, Jilin Grain and Oil Hygiene Inspection and Monitoring Station.
Main drafters of this standard: Yuan Jian, Yang Xiaorong, Dai Bo, Wang Haifeng, Mo Xiaosong, Yu Xiaohe, Gao Xiaochun.
The clauses in the following documents become clauses of this standard through reference in this standard. For all dated referenced documents, all subsequent amendments (excluding errata) or revisions are not applicable to this standard. However, the parties to the agreement based on this standard are encouraged to study whether the latest versions of these documents can be used. For all undated referenced documents, the latest versions are applicable to this standard.
GB5491 Sampling and splitting methods for grain and oilseed inspection
GB/T6682 Specifications and test methods for water used in analytical laboratories

ICS 67.060
National Standard of the People's Republic of China
GB/T 25222-2010
Inspection of grain and oils
Deternination of phosphide residues in grain-Spectropholometric method
2010-09-26 Issued by
General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China Standardization Administration of China
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2011-03-01 implementation
People's Republic of China
National Standard
Grain and Oil Inspection
Determination of Phosphate Residues in Grains
Spectrophotometric Method
GE/T25222—2010
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This standard is proposed by the State Grain Administration.
This standard is under the jurisdiction of the National Technical Committee for Grain and Oil Standardization. The responsible drafting unit of this standard: Nanjing University of Finance and Economics. GB/T 25222--2010
The participating drafting units of this standard: Jiangsu Grain and Oil Quality Supervision and Inspection Institute, Fujing Grain and Oil Quality Supervision and Inspection Institute, Jilin Grain and Oil Hygiene Inspection and Monitoring Station.
The main drafters of this standard: Yuan Jian, Yang Xiaorong, Dai Bo, Wang Haifeng, Ying Xiaosong, Yu Xiaohe, Gao Xiaotun. 1
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Grain and Oil Inspection Determination of Phosphate Residues in Grains Spectrophotometric Method
GB/T 25222—2010
This standard specifies the terms and definitions, principles, reagents and materials, instruments and equipment, sampling, sample preparation, operating procedures, result calculation and expression for the determination of phosphide residues in grains by spectrophotometry. This standard is applicable to the determination of phosphide fumigant residues in grains. The detection limit of this standard method is 0.01 mg/kg. 2 Normative referenced documents
The clauses in the following documents become the clauses of this standard through reference in this standard. For any dated referenced document, all subsequent amendments (excluding errata or revised versions) are not applicable to this standard. However, parties that reach an agreement based on this standard are encouraged to study whether the latest versions of these documents can be used. For any referenced document without a date, its latest version applies to this standard. (GB5491 Sampling and subsampling method for grain and oil inspection GB/T6682 Specifications and test methods for water for analytical laboratories 3 Terms and definitions
The following terms and definitions apply to this standard. 3.1
Phosphide
Phosphorus-containing compounds used as fumigants, such as aluminum phosphide. 3.2
Phosphide residue residues The content of phosphide residues in grain measured under the conditions specified in this standard. It is expressed as the mass fraction of phosphine in the sample. 4 Principle
Under the action of water and acid, the phosphide in the sample generates phosphine gas, which evaporates and is absorbed in the acidic potassium permanganate solution and oxidized into phosphoric acid, and then reacts with ammonium permanganate to generate ammonium phosphate, which is reduced with stannous chloride to form a blue compound blue, and its absorbance is measured and quantified using the standard curve method.
5 Reagents and materials
Unless otherwise specified, all reagents used are analytically pure, and the experimental water should meet the requirements of Grade 3 in GB/T6682. 5.1 Potassium permanganate solution (16.5g/1.): Weigh 16.5g of potassium permanganate, add water to dissolve the tablet and dilute to 1000tml., let it stand for three days or boil it for 3 hours. rnit1, cool, place overnight, filter with glass wool or asbestos for later use. 5.2 Potassium permanganate solution (3.3g/L): Take a certain amount of potassium permanganate solution (5.1) and dilute it 5 times with water. 5.3 Combustible acid (l+17): Take 28mL 98% sulfuric acid and slowly add it to 400mL water, add 500mL water after cooling, 5.4 Sulfuric acid (1+5): Take 83.3ml. 98% sulfuric acid and slowly add it to 400mL water, add water to 500mL after cooling. 5.5 Saturated sodium sulfite solution: Take 28.5g anhydrous sodium sulfite, add about 70ml. water, heat slightly to dissolve, dilute to 100mL after cooling, 5.6 Ammonium molybdate solution: 50g/L.
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GB/T 25222—2010
5.7 Sodium chloride solution: Take 0.1% tin chloride and dissolve it in 5mL hydrochloric acid. Prepare it before use. 5.8 Acidic potassium permanganate solution: Mix potassium permanganate solution (5.1) and sulfuric acid (5.3) in equal amounts. 5.9 Alkaline pyrogallic acid solution: Dissolve 5g pyrogallic acid in 15mL water, and 48g potassium hydroxide in 32mL water. After cooling, carefully mix the two solutions. Prepare it before use. 5.10 Phosphide standard solution: Weigh 0.0400g of anhydrous potassium dihydrogen phosphate dried at 105℃, dissolve it in water, transfer it into a 100mL volumetric flask, and dilute it to the mark with water (1 drop of trichloroethane can be added to increase the storage time). The phosphorus content of this solution is equivalent to 0.10ng/ml of phosphine. 5.11 Phosphide standard solution Pipette 1.00 mL phosphide standard solution (5.10) into a 100 l volumetric flask, add water to the mark, and mix. The solution contains phosphorus equivalent to 1.0 g/ml of phosphine. 6 Instruments and equipment
Laboratory routine instruments and equipment and the following instruments and equipment. 6.1 Spectrophotometer: with 3 cm cuvette, adjustable wavelength 710 nm. 6.2 Balance with a sensitivity of 0.01 g and a sensitivity of 0.0001 g. 6.3 Phosphate distillation and absorption device, including the following glassware and instruments. Figure 1. Connect the vacuum pump
Gas washing bottle:
Separating funnel:
Reaction bottle;
6, 7, 8-
- Gas absorption tube:
Iron stand.
Figure 1 Phosphine distillation absorption device
6.3.1 Gas absorption tube: 20 mL.
6.3.2 Gas washing bottle: 250 ml..
6.3.3 Separating funnel: 250 mL, equipped with a rubber stopper matching the three-necked flask. 6.3.4 Boiling water bath: copper water bath pot and electric furnace, or other equivalent equipment. 6.3.5 Hydraulic vacuum pump or other vacuum equipment: adjustable vacuum speed. 6,3,6 Reaction flask; three-necked flask, 1 000 ml.. 6.3.7 Glass tube: 1 long tube and 1 short tube, with a rubber stopper matching the reaction flask, or a ground-joint tube that can be connected to the reaction flask. Note: The long tube should be able to extend at least 2 cm below the reaction liquid surface, and the part of the short tube in the reaction flask should not be too long. 6.3.8 Iron stand; equipped with a 1-shaped clamp and a square clamp. 6.3.9 Hose: rubber or latex tube.
6.4 Colorimetric tube: 50mL,
6.5 Graduated pipette: 1mL, 5ml. Several of each 6.6 Pipettes: 10 tnL, 100 tnL.
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7 Sampling
Perform according to CB5491 and seal the package immediately. 8 Sample preparation
After opening the package, take the sample as quickly as possible according to (B5491. Granular grain samples do not need to be crushed.
9 Operating steps
9.1 Preparation of distillation and absorption device
GB/T25222--2010
Connect the distillation and absorption device according to Figure 1. Add 5ml of potassium permanganate solution (5.2) and 1ml of sulfuric acid (5.3) to each of the three gas absorption tubes (6.3.1) connected in series. Add about 100ml of acidic potassium permanganate solution (5.8) to washing bottle 1 (6.3.2), and add freshly prepared alkaline pyrogallic acid solution (5.9) to washing bottle 2 (6.3.2): Add 5ml of sulfuric acid (5.9) to the separating funnel (6.3.3).3) and 80mL of water. Add an appropriate amount of water to the water bath (6.3.4) and heat to boiling. Turn on the vacuum pump (6.3.5), check the air tightness of the device, 9.2
9.2.1 Weigh 50g (accurate to 0.1g) of the sample. 9.2.2 Pre-evacuate for 5min, remove the separatory funnel (6.3,3), quickly add the sample (9.2.1) to the reaction bottle (6.3.6), immediately install the separatory funnel, plug the bottle stopper, increase the vacuum speed, add the solution in the separatory funnel to the reaction bottle, then slow down the vacuum speed, vacuum for 30min, and keep the water bath boiling.
Transfer: During the reaction, the vacuum speed should be such that the gas pool can be distinguished. 9.2.3 After the reaction is completed, first remove the connection of the gas absorption tube (6.3.1) at the inlet end, then remove the connection of the exhaust tube - end, turn off the exhaust, remove the three gas absorption tubes, combine the solution in the absorption tubes into a 50-mL colorimetric tube (6, 4), wash the gas absorption tube with a small amount of water, add the washing liquid into the colorimetric tube, drop saturated sodium sulfate solution (5.5) to decolorize the potassium permanganate solution, add 4.5 mL sulfuric acid (5.4), 2.5 mL ammonium sulfate solution (5.6), mix, then add water to the 50 mL mark and mix. 9.2.4 Add 0.1 mL of tiron iodide solution (5.7) to the colorimetric tube (9.2.3), mix. After 165 minutes, use a 3 cm colorimetric cup, adjust the zero point with a zero arm, measure the absorbance at a wavelength of 710 nm, and calculate the corresponding phosphide content on the standard curve. 9.3 Preparation of standard curve
Pipette 0 mL, 1.00 mL, 2.00 mL, 3.00 mL, 4.00 mL, 5.00 mL of phosphide standard solution (5.11) (equivalent to 0 μg, 1 μg, 2 μg, 3 μg, 4 μg, 5 μg of phosphine) and add them to 6 50 mL colorimetric tubes (6.4) respectively. Then add 30 mL of water, 5.5 mL of sulfuric acid (5.4), 2.5 mL of ammonium sulfate solution (5.6) to each tube, mix, add water to 50 mL, mix. Then add 0.1 mL of sodium chloride solution (5.7) and mix. After 15 minutes, use a 3 cm colorimetric cup and adjust the zero point with a zero tube. Measure the absorbance at a wavelength of 710 nm and draw a standard curve of the relationship between phosphine content and absorbance.
9.4 Blank test
Except for not adding the sample, add various reagents to conduct a blank test according to the determination steps in 9.2. 9.5 Parallel test
Each sample shall be tested twice according to 9.1~-9.2. 10 Calculation and expression of results
10.1 The residual amount of phosphide in the sample is calculated according to formula (1); X=(A,
A,) ×1000
rX1000
Wu Zhong:
X——Residual amount of phosphide in the sample (in pHs), in milligrams per kilogram (mg/kg): Snow Product Partner Network ht
GR/T 25222-2010
A, the mass of phosphide in the sample solution, in micrograms (μg); the mass of phosphide in the blank solution of A2 reagent, in micrograms (ug); m---the mass of the sample, in grams (g).
10.2 Expression of results: The results of two parallel determinations shall meet the requirements of repeatability (Chapter 11). The arithmetic mean of the two determinations shall be the final determination result, and two significant figures shall be retained. 11
Repeatability requirements
The difference between two determination results should not exceed 10% of the average value. Copyright exclusive infringement must be investigated
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GB/T25222-2010
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