Some standard content:
ICS 67.040
National Standard of the People's Republic of China
GB/T5009.36—2003
Replaces GB/T5009.36—1996
Method for analysis of hygienic standard of grains
Promulgated on 2003-08-11
Ministry of Health of the People's Republic of China
Standardization Administration of the People's Republic of China
Implementation on 2004-01-01
GB/T5009.36—2003
This standard replaces GB/T5009.36—1996 "Method for analysis of hygienic standard of grains". Compared with GB/T5009.36-1996, this standard has been modified as follows: The structure of the original standard has been modified in accordance with GB/T20001.4-2001 "Standard Preparation Rules Part 4: Chemical Analysis Methods".
This standard is proposed and managed by the Ministry of Health of the People's Republic of China. This standard was drafted by the Institute of Nutrition and Food Hygiene of the Chinese Academy of Preventive Medicine, the Food Hygiene Supervision and Inspection Institute of the Ministry of Health, the Guangdong Food Hygiene Supervision and Inspection Institute, the Tianjin Municipal Health and Epidemic Prevention Station, the Dalian Food Hygiene Inspection Institute, the Qinhuangdao Food Hygiene Inspection Institute, and the State Administration of Import and Export Commodity Inspection of the People's Republic of China.
This standard was first issued in 1985 and revised for the first time in 1996. This is the second revision. 286
1 Scope
Analysis methods for food hygiene standards
This standard specifies the analysis methods for various hygiene indicators in raw grains and finished grains. GB/T5009.36—2003
This standard applies to the analysis of sanitary indicators such as malathion, phorate, molluscamide, fenthion, dichlorvos, dimethoate, parathion, phosphide, cyanide, chloropicrin, carbon disulfide, arsenic, mercury, hexachloride, DDT, aflatoxin B, cadmium, fluorine, Datura seeds, ergot, ethylene dibromide, heptachlor, aldrin, and dieldrin in raw and finished grains. 2 Normative references
The clauses in the following documents become the clauses of this standard through reference in this standard. For all dated references, 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 references, the latest versions are applicable to this standard. GB/T5009.11 Determination of total arsenic and inorganic arsenic in foodGB/T5009.15 Determination of cadmium in food
GB/T5009.17 Determination of total mercury and methylmercury in foodGB/T 5009.18
3 Determination of fluorine in food
GB/T5009.19
GB/T5009.20
GB/T5009.22
3 Sensory examination
Determination of BHC and DDT residues in foodDetermination of organophosphorus pesticide residues in foodDetermination of aflatoxin B in food
It should have the color and smell of normal grain and should not be moldy or deteriorated. 4 Physical and chemical tests
4.1 Malathion
4.1.1 Gas chromatography
Operate according to GB/T5009.20.
4.1.2 Copper complex colorimetry
4.1.2.1 Principle
Malathion is extracted with an organic solvent and hydrolyzed with sodium hydroxide to generate dimethyl dithiophosphate, which then reacts with copper salt to generate a yellow complex, which is quantitatively compared with the standard series.
When the sample size is 20g, the detection limit of this method is 1.25mg/kg. 4.1.2.2 Reagents
4.1.2.2.1 Carbon tetrachloride.
4.1.2.2.2 Anhydrous ethanol.
4.1.2.2.3 Sodium sulfate solution (45g/L): Weigh 4.5g of anhydrous sodium sulfate, dissolve in water, and dilute to 100mL. 4.1.2.2.4 Acidic sodium sulfate solution: Add 2.5mL of hydrochloric acid to 100mL of sodium sulfate solution (45g/L) and mix well. 4.1.2.2.5 Carbon disulfide-carbon tetrachloride mixture (1+200). 4.1.2.2.6 Hydrochloric acid (1+1): Take 50mL of hydrochloric acid and dilute to 100mL with water. 4.1.2.2.7
Sodium hydroxide solution (240g/L): Take 24g of sodium hydroxide and dissolve in water to 100mL. 287
GB/T5009.36—2003
4.1.2.2.8 Ferric chloride solution (50g/L). 4.1.2.2.9 Copper sulfate solution (35 g/L): weigh 3.5 g of copper sulfate (CuSO,·5H,O) and dissolve it in 100 mL of water. 4.1.2.2.10 Phenol-ethanol indicator solution (10 g/L): weigh 1 g of phenolic acid, dissolve it in ethanol (95%) and dilute it to 100 mL. 4.1.2.2.11 Malathion standard solution: first accurately weigh a 50 mL volumetric flask, then drop about 50 mg of malathion into it, then accurately weigh it again, add carbon tetrachloride to the scale, mix well, and calculate its concentration. 4.1.2.2.12 Malathion standard working solution: before use, add carbon tetrachloride to the malathion standard solution and dilute it to 100.0 μg of malathion per milliliter.
4.1.2.3 Instruments and equipment
Spectrophotometer.
4.1.2.4 Analysis steps
Weigh about 20.00g of the sample that has been crushed and completely passed through a 20-mesh sieve, place it in a 200mL stoppered conical flask, add 40mL of carbon tetrachloride, seal it, shake for 2h, and then filter.
Pipette 20mL of the filtrate into a 125mL separatory funnel, add 0.2ml of carbon disulfide-carbon tetrachloride mixture, add 10mL of acidic sodium sulfate solution, shake for 1min, let stand to separate, transfer the carbon tetrachloride layer into another separatory funnel, and discard the water layer. Pipette 0, 0.5, 1.0, 1.5, 2.0, 2.5mL of malathion standard working solution (equivalent to 0, 50, 100, 150, 200, 250μg malathion), place it in a 125mL separatory funnel respectively, add carbon tetrachloride to 20mL, and then add 0.2mL of carbon disulfide-carbon tetrachloride mixture to each. Add 5 mL of anhydrous ethanol to the sample solution and malathion standard solution, add 0.4 mL of sodium hydroxide solution (240 g/L), shake vigorously for 1 min, immediately add 10 mL of sodium sulfate solution (45 g/L), mix well, add 1 drop of phenol indicator solution, neutralize with hydrochloric acid (1+1) until the phenol fades, then adjust the pH to 3-4 with hydrochloric acid (1+11) (pH test paper test), add 0.5 mL of ferric chloride solution (50 g/L), shake for 1 min, let stand to separate (if emulsified, centrifuge to separate), discard the carbon tetrachloride layer, wash the water layer with 2 mL of carbon tetrachloride, shake for 1 min, discard the carbon tetrachloride layer after separation, if the carbon tetrachloride layer is yellow, wash the water layer with carbon tetrachloride. Accurately add 4.0 ml of carbon tetrachloride and 0.5 mL of copper sulfate solution (35 g/L) to the water layer, and shake accurately for 1 min. After standing for stratification, filter the carbon tetrachloride layer through absorbent cotton into a 2 cm colorimetric cup, adjust the zero point with carbon tetrachloride, measure the absorbance at a wavelength of 415 nm within 20 minutes, and draw a standard curve for comparison. 4.1.2.5 Calculation of results
The content of malathion in the sample is calculated according to formula (1). X
AX1000
m×V,/V/X1000
Where:
X is the content of malathion in the sample, in milligrams per kilogram (mg/kg); A is the mass of malathion in the sample solution for determination, in micrograms (μg); m is the mass of the sample, in grams (g);
V, is the total volume of the sample extracted with carbon tetrachloride, in milliliters (mL); V is the volume of the carbon tetrachloride extract of the sample for determination, in milliliters (mL). The calculation result should retain two significant figures.
4.2 Phorate, molluscamide, fenthion, dichlorvos, dimethoate and parathion are measured by gas chromatography according to GB/T5009.20. 4.3 Phosphides
4.3.1 Qualitative
4.3.1.1 Principle
Phosphides release phosphine when in contact with water and acid, and react with silver nitrate to form black silver phosphide. If sulfide is present, hydrogen sulfide is also released, and reacts with silver nitrate to form black silver sulfide, which interferes with the determination. Hydrogen sulfide can react with lead acetate to form black lead sulfide, which can be used to prove whether there is sulfide interference. 4.3.1.2 Reagents
4.3.1.2.1 Tartaric acid.
4.3.1.2.2 Silver nitrate solution (100g/L): Store in a brown bottle. 4.3.1.2.3 Lead acetate solution (100g/L). 4.3.1.2.4 Acetic acid solution (100g/L). 4.3.1.3 Apparatus
GB/T5009.36—2003
Take a 200mL~250mL conical flask, equip it with a suitable double-hole cork or rubber stopper, plug each hole with a glass tube with an inner diameter of 0.4cm~0.5cm and a length of 5cm, and hang a filter paper strip with a length of 7cm and a width of 0.3cm~0.5cm in each tube. When using, wet one strip with silver nitrate solution and the other with lead acetate solution. 4.3.1.4 Analysis steps
Quickly weigh 20.00g of the sample, place it in a conical flask, add appropriate amount of water to immerse the sample, and then add about 0.5g of tartaric acid, immediately plug the prepared double-hole stopper, so that the end of the filter paper strip is about 5cm away from the liquid surface, heat it in a water bath at 40℃~50℃ in the dark for 30min, and observe the color change of the test paper. If the test papers do not change color, it indicates that the phosphide has a negative reaction or does not exceed the specified value. If the silver nitrate test paper changes color and the lead acetate test paper does not change color, it indicates that phosphide may exist and needs to be re-quantified. If both test papers change color, it may be that phosphide and sulfide exist at the same time or only sulfide exists. In this case, re-take the sample, add water and then add 5mL cadmium acetate solution (100g/L) to form a yellow cadmium sulfide precipitate, immediately seal it, leave it for 10 minutes, and then add tartaric acid. The operation is the same as before. If the silver nitrate test paper turns black and the lead acetate test paper does not change color, it indicates that phosphide exists and needs to be re-quantified. 4.3.2 Quantification
4.3.2.1 Principle
Phosphide releases phosphine when it meets water and acid. After evaporation, it is absorbed in acidic potassium permanganate solution and oxidized into phosphoric acid. It reacts with ammonium molybdate to form ammonium phosphoaluminate. It is reduced to a blue compound molybdenum blue when it meets stannous chloride. It is quantified by comparing with the standard series. When the sample size of this method is 50g, the detection limit is 0.020mg/kg. 4.3.2.2 Reagents
4.3.2.2.1 Potassium permanganate solution (16.5g/L): Weigh 16.5g potassium permanganate, dissolve it in water and dilute it to 1000mL, let it stand for three days or boil it for 3min, cool it, leave it overnight, filter it with glass wool or asbestos for later use. 4.3.2.2.2 Potassium permanganate solution (3.3g/L): Dilute potassium permanganate solution (16.5g/L) 5 times with water. 4.3.2.2.3 Sulfuric acid (1+17): Take 28mL of sulfuric acid and slowly add it to 400mL of water, cool it and add water to 500mL. 4.3.2.2.4 Sulfuric acid (1+5): Take 83.3mL of sulfuric acid and slowly add it to 400mL of water, cool it and add water to 500mL. 4.3.2.2.5 Saturated sodium sulfite solution: Take 28.5g of anhydrous sodium sulfite, add about 70mL of water, dissolve it with slight heat, cool it down, and dilute it to 100ml.
4.3.2.2.6 Ammonium molybdate solution (50g/L). 4.3.2.2.7 Stannous chloride solution: Take 0.1g of stannous chloride and dissolve it in 5mL of hydrochloric acid. Prepare it before use. 4.3.2.2.8 Phosphide standard solution: Accurately weigh 0.0400g of anhydrous potassium dihydrogen phosphate dried at 105℃, dissolve it in water, transfer it to a 100mL volumetric flask, and dilute it to the mark with water (1 drop of chloroform can be added to increase the storage time). Each milliliter of this solution is equivalent to 0.10mg of phosphine.
4.3.2.2.9 Phosphide standard solution: Pipette 10.0mL of phosphide standard solution, place in a 100mL volumetric flask, add water to the mark, mix well, each mL of this solution is equivalent to 10μg of phosphine. 4.3.2.2.10 Hydrochloric acid (1+1).
4.3.2.2.11 Saturated mercuric nitrate solution.
4.3.2.2.12 Saturated hydrazine sulfate solution.
4.3.2.2.13 Acidic potassium permanganate solution: Mix equal amounts of potassium permanganate solution (16.5g/L) and sulfuric acid (2mol/L). 4.3.2.3 Instrument
The instrument is shown in Figure 1.
GB/T5009.36-2003
1.6-—Separatory funnel;
2—Carbon dioxide generating bottle;
3, 4.5—Gas washing bottle;
7—Water bath;
8-Reaction bottle;
9, 10, 11—Gas absorption tube.
4.3.2.4 Analysis steps
Sample determination: Add 5mL potassium permanganate solution (3.3g/L) and 1mL sulfuric acid (1+17) to each of the three connected gas absorption tubes. The carbon dioxide generating bottle is filled with marble fragments. Add an appropriate amount of hydrochloric acid (1+1) from the separatory funnel 1 as a carbon dioxide generator. The carbon dioxide gas is washed in sequence by a washing bottle filled with saturated mercuric nitrate solution, acidic potassium permanganate solution, and saturated hydrazine sulfate solution, and then enters the reaction bottle (if nitrogen is used instead of carbon dioxide, it can directly enter the reaction bottle through the hydrazine sulfate solution safety bottle). Pre-pass carbon dioxide (or nitrogen) for 5 minutes, open the stopper of the reaction bottle, quickly put in the weighed 50g sample, immediately plug the bottle, increase the suction speed so that 5mL sulfuric acid (1+17) and 80mL water in the separatory funnel 6 are added to the reaction bottle, then slow down the suction and carbon dioxide (or nitrogen) gas flow speed, heat the water bath where the reaction bottle is placed to boiling for 30 minutes, and continue to pass carbon dioxide (or nitrogen). After the reaction is completed, first remove the end of the gas absorption tube for air inlet, then remove one end of the suction tube, remove the three gas absorption tubes, drop saturated sodium sulfite solution to make the potassium permanganate solution white, combine the solution in the absorption tube into a 50mL colorimetric tube, wash the gas absorption tube with a small amount of water, and add the washing liquid into the colorimetric tube, add 4.4mL sulfuric acid (1+5), 2.5mL ammonium molybdate solution (50g/L), and mix well. Take 0, 0.1, 0.2, 0.3, 0.4, 0.5mL of phosphide standard solution (equivalent to 0, 1, 2, 3, 4, 5g of phosphine) and put them into 50mL colorimetric tubes respectively, add 30mL of water, 5.4mL of sulfuric acid (1 + 5), 2.5mL of ammonium molybdate solution (50g/L), and mix well. Add water to 50mL in the sample and standard tubes respectively and mix well, then add 0.1mL of stannous chloride solution to each tube and mix well. After 15 minutes, use a 3cm colorimetric cup and a zero tube to adjust the zero point, measure the absorbance at a wavelength of 680nm, draw a standard curve for comparison, or visually compare with the standard series. Take the same amount of reagent as the treated sample and perform a reagent blank test according to the same operation method. 4.3.2.5 Calculation of results
The content of phosphide in the sample is calculated according to formula (2). X=(AA)×1000
mx1000
wherein:
X is the content of phosphide in the sample (calculated as phosphine), in milligrams per kilogram (mg/kg); A, is the mass of phosphide in the sample for determination, in micrograms (pg); Az
is the mass of phosphide in the reagent blank, in micrograms (μg); (2)
is the mass of the sample, in grams (g).
The calculation result shall retain two significant figures.
GB/T5009.36—2003
4.3.2.6 Replace carbon dioxide with air. The air is washed in the gas washing bottle containing acidic potassium permanganate solution and alkaline pyrogallic acid solution (5g pyrogallic acid is dissolved in 15mL water, 48g potassium hydroxide is dissolved in 32mL water, and then the two liquids are mixed) and then enters the reaction bottle. The following operations are the same as above. The device is shown in Figure 2. 1.2-gas washing bottle;
3-separating funnel;
4-reaction bottle;
5-water bath:bzxz.net
6, 7, 8-gas absorption tube.
4.4 Cyanide
4.4.1 Qualitative
4.4.1.1 Principle
Cyanide generates hydrocyanic acid when it meets acid, and hydrocyanic acid reacts with sodium picrate to generate red sodium isocyanate. 4.4.1.2 Reagents
4.4.1.2.1 Tartaric acid.
4.4.1.2.2 Sodium carbonate solution (100g/L). 4.4.1.2.3 Picric acid test paper: Cut the qualitative filter paper into strips with a length of 7cm and a width of 0.3cm~0.5cm, immerse them in saturated picric acid-ethanol solution, take them out after a few minutes, dry them in the air, and store them for later use. 4.4.1.3 Apparatus
Take a 200mL~300ml conical flask, equip it with a suitable single-hole cork or rubber stopper, plug the hole with a glass tube with an inner diameter of 0.4cm~0.5cm and a length of 5cm, and hang a picric acid test paper in the tube. When using, moisten the test paper with sodium carbonate solution (100g/L). 4.4.1.4 Analysis steps
Quickly weigh 5g of the sample and place it in a 100mL conical flask, add 20mL of water and 0.5g tartaric acid, immediately plug the wooden stopper of the test paper with picric acid and moistened with sodium carbonate, place it in a water bath at 40℃～50℃, heat it for 30min, and observe the color change of the test paper. If the test paper does not change color, it means that the cyanide has a negative reaction or does not exceed the specified value: if the test paper changes color, it is necessary to do another quantitative test. 4.4.2 Quantification
4.4.2.1 Principle
After the cyanide is evaporated in the acidic solution, it is absorbed in the alkaline solution. In the pH 7.0 solution, chloramine T is used to convert the cyanide into cyanogen chloride, and then reacts with isonicotinic acid-pyrazolone to generate a blue dye, which is compared with the standard series for quantitative analysis. 291
GB/T5009.36—2003
When the sample size of this method is 10g, the detection limit is 0.015mg/kg. 4.4.2.2 Reagents
4.4.2.2.1 Methyl orange indicator solution (0.5 g/L). 4.4.2.2.2 Zinc acetate solution (100 g/L). 4.4.2.2.3
Tartaric acid.
4.4.2.2.4 Sodium hydroxide solution (10 g/L). 4.4.2.2.5 Sodium hydroxide solution (1 g/L). 4.4.2.2.6 Acetic acid (1+24).
4.4.2.2.7 Phenolyl-ethanol indicator solution (10 g/L). 4.4.2.2.8 Phosphate buffer solution [(0.5 mol/L) pH 7.0]: Weigh 34.0 g anhydrous potassium dihydrogen phosphate and 35.5 g anhydrous disodium hydrogen phosphate, dissolve in water and dilute to 1000 mL. 4.4.2.2.9 Solution of silanol (p-dimethylaminobenzyl rhodanine): weigh 0.02g of silanol and dissolve it in 100mL of acetone. 4.4.2.2.10 Solution of isonicotinic acid-pyrazolone: weigh 1.5g of isonicotinic acid and dissolve it in 24mL of sodium hydroxide solution (20g/L), add water to 100mL, weigh 0.25g of pyrazolone and dissolve it in 20mL of N-dimethylformamide, combine the above two solutions and mix well. 4.4.2.2.11 Solution of chloramine T: weigh 1g of chloramine T (the effective chlorine content should be above 11%) and dissolve it in 100mL of water, prepare it before use.
4.4.2.2.12 Potassium cyanide standard solution: Weigh 0.25g potassium cyanide, dissolve in water, and dilute to 1000mL. This solution is equivalent to approximately 0.1mg cyanide per milliliter. Its accuracy can be calibrated by the following method before use. Take 10.0mL of the above solution, place it in a conical flask, add 1mL sodium hydroxide solution (20g/L) to make the pH above 11, add 0.1mL silver nitrate solution, and titrate with silver nitrate standard solution (0.020mol/L) until it turns orange-red [1mL silver nitrate standard solution (0.020mol/L) is equivalent to 1.08mg hydrocyanic acid 1. 4.4.2.2.13 Potassium cyanide standard working solution: Take an appropriate amount according to the concentration of potassium cyanide standard solution, and dilute it with sodium hydroxide solution (1g/L) to 1ug hydrocyanic acid per milliliter.
4.4.2.3 Instruments
4.4.2.3.1 250mL glass water vapor filling steaming device. 4.4.2.3.2 Spectrophotometer.
4.4.2.4 Analysis steps
Quickly weigh 10.00g of the sample and place it in a 250mL distillation flask. Add appropriate amount of water to immerse the sample completely. Add 20mL of zinc acetate solution (100g/L) and 1g~2g of tartaric acid. Quickly connect all the devices. Insert the lower end of the condenser tube under the liquid surface of a 100mL volumetric flask containing 5mL of sodium hydroxide solution (10g/L). Slowly heat and distill with water vapor. Collect nearly 100mL of distillate, remove the volumetric flask, add water to the scale, mix with a spoon, and take 10mL of the filling steaming liquid and place it in a 25mL colorimetric tube. Pipette 0.0.3.0.6, 0.9, 1.2, 1.5mL of cyanide standard solution (equivalent to 0.0.30.6, 0.9, 1.2, 1.5μg of hydrocyanic acid) into 25mL colorimetric tubes, add water to 10mL each. Add 1mL of sodium hydroxide solution (10g/L) and 1 drop of phenol indicator solution to the sample solution and standard solution, adjust with acetic acid (1+24) until the red color just disappears, add 5mL of phosphate buffer solution, heat to about 37℃, add 0.25mL of chloramine T solution, add stopper to mix, place for 5min, then add 5mL of isonicotinic acid-pyrazolone solution, add water to 25mL, mix well, place at 25℃～40℃ for 40min, use a 2cm colorimetric cup, adjust the zero point with a zero tube, measure the absorbance at a wavelength of 638nm, and draw a standard curve for comparison.
4.4.2.5 Calculation of results
The content of cyanide (calculated as hydrocyanic acid) in the sample is calculated according to formula (3). AX1000
mxV./V×1000
Wherein:
X--the content of cyanide (calculated as hydrocyanic acid) in the sample, in milligrams per dry gram (mg/kg); 292
A--the mass of hydrocyanic acid in the sample liquid for determination, in micrograms (μg); m
the mass of the sample, in grams (g);
V--the total volume of the sample distillate, in milliliters (mL); V, the volume of the distillate for determination, in milliliters (mL). The calculation result shall retain two significant figures.
4.5 Chloropicrin
4.5.1 Principle
GB/T5009.36-2003
Chloropicrin can be decomposed by sodium ethoxide to form nitrite, which is diazotized with aminobenzenesulfonic acid in a weak acid solution, and then coupled with N-1-naphthylethylenediamine hydrochloric acid to generate purple-red color, which is quantitatively compared with the standard series. When the sample size is 20g, the detection limit of this method is 0.050mg/kg. 4.5.2 Reagents
4.5.2.1 Sodium ethoxide solution: Take metallic sodium, first use filter paper to absorb the kerosene on the surface, and use a knife to cut off the oxidized part of the surface (be sure to put the surface part back into the kerosene after cutting it off, and do not let it come into contact with water), then take 5g and cut it into pieces, measure 1000mL of anhydrous ethanol, put it in a large beaker, and immediately add the cut metallic sodium in batches. When the reaction is complete and no gas is generated in the beaker, move it into a brown bottle for later use. 4.5.2.2 Anhydrous ethanol.
4.5.2.3 p-Aminobenzenesulfonic acid solution (4g/L): Weigh 0.4g p-Aminobenzenesulfonic acid and dissolve it in 100mL of hydrochloric acid (1+1), and store it in a brown bottle.
4.5.2.4 N-1-naphthylethylenediamine solution (2g/L): Weigh 0.2g N-1-naphthylethylenediamine and dissolve it in 100mL water. Store in a brown bottle.
4.5.2.5 Chloropicrin standard stock solution: Measure about 20mL of anhydrous ethanol and place it in a 50mL volumetric flask. After accurate weighing, add 2 drops of chloropicrin and weigh it again accurately. The difference between the two times is the mass of chloropicrin. Add anhydrous ethanol to the scale and mix. 4.5.2.6 Chloropicrin standard working solution: Take an appropriate amount of chloropicrin standard stock solution and place it in a 50mL volumetric flask. Add anhydrous ethanol to dilute to the scale. Each milliliter of this solution should be equivalent to 0.020mg chloropicrin. Store in a refrigerator. 4.5.3 Instruments
Spectrophotometer.
4.5.4 Analysis steps
Weigh about 20.00g of the sample, place it in a 100mL stoppered conical flask, add 20mL of sodium ethoxide solution, cover it, place it in a dark place for 8h~10h or overnight, filter it, measure 5.0mL of the filtrate, and place it in a 10mL colorimetric tube. Pipette 5.0mL of chloropicrin standard working solution, place it in a 50mL volumetric flask, add 20mL of sodium ethoxide solution, place it in a dark place for 8h~10h or overnight, then add anhydrous ethanol to dilute to the scale, then pipette 0, 1.0, 2.0, 3.0, 4.0, 5.0mL of this solution (equivalent to 0, 2, 4.6, 8, 10μg of chloropicrin), place it in 10mL colorimetric tubes respectively, then add anhydrous ethanol to 5mL each, and add 1mL of acetic acid (36%). Add 1 mL of p-aminobenzenesulfonic acid (4 g/L) to each sample and standard tube, mix well, let stand for 3 to 5 minutes, then add 0.5 mL of N-1-naphthylethylenediamine solution (2 g/L) to each tube, add anhydrous ethanol to the scale, mix well and let stand for 20 minutes, use a 1 cm colorimetric cup, adjust the zero point with a zero tube, measure the absorbance at a wavelength of 538 nm, and draw a standard curve for comparison. 4.5.5 Calculation of results
The content of chloropicrin in the sample is calculated according to formula (4). AX1000
X-mxV.N.X1 000
Wherein:
X—the content of chloropicrin in the sample, in milligrams per kilogram (mg/kg); A—the mass of chloropicrin in the sample for determination, in micrograms (μg); V—the total volume of sodium ethoxide added to the sample, in milliliters (mL); V—the volume of the sample filtrate for determination, in milliliters (mL); (4)
GB/T5009.36-2003
Sample mass, in grams (g).
Calculation results should be rounded to two significant figures.
4.6 Carbon disulfide
4.6.1 Principle
Carbon disulfide reacts with diethylamine to form diethylamine sulfonic acid, which then reacts with copper salt to form a yellow complex salt, which is quantitatively compared with the standard series. When the sample size is 25g, the detection limit of this method is 0.20mg/kg. 4.6.2 Reagents
4.6.2.1 Diethylamine-ethanol solution (10g/L). 4.6.2.2 Copper acetate-ethanol solution (0.5g/L). 4.6.2.3 Copper sulfate solution (50g/L).
4.6.2.4 Carbon disulfide standard stock solution: Take about 20mL of diethylamine-ethanol solution (10g/L) and place it in a 50mL volumetric flask. After accurate weighing, add 2 drops of carbon disulfide and weigh accurately again. The difference between the two is the mass of carbon disulfide. Add diethylamine-ethanol solution (10g/L) to the scale and mix.
4.6.2.5 Carbon disulfide standard working solution: Take an appropriate amount of carbon disulfide standard solution and place it in a 50mL volumetric flask. Add diethylamine-ethanol solution (10g/L) to dilute to the scale. Each milliliter of this solution is equivalent to 0.020mg of carbon disulfide. 4.6.2.6 Ethanol (95%).
4.6.3 Instruments
4.6.3.1 Apparatus: as shown in Figure 3.
4.6.3.2 Spectrophotometer.
1, 2——gas absorption tube;
3——round bottom flask;
4——water bath;
5-—gas washing bottle.
4.6.4 Analysis steps
Weigh about 25.00g of sample, place it in a 500mL round bottom flask, add appropriate amount of water to immerse the sample, add 10mL of diethylamine-ethanol solution (10g/L) to each gas absorption tube, add 50mL of copper sulfate solution (50g/L) to the gas washing bottle to remove sulfide in the air, then place the round bottom flask in a water bath at about 70℃, connect the gas washing bottle, absorption tube and exhaust device according to Figure 3, and remove the gas absorption tube after exhausting for 2h. Stop heating and exhausting. Pour the absorption liquid in the gas absorption tube into a 50mL volumetric flask, wash the gas absorption tube 2 to 3 times with a small amount of diethylamine-ethanol solution (10g/L), add the washing liquid into the volumetric flask, add diethylamine-ethanol solution (10g/L) to the scale, and mix. Pipette 5.0mL and place it in a 25mL colorimetric tube.
Pipette 0.0.5, 1.0, 1.5, 2.0, 2.5mL of carbon disulfide standard solution (equivalent to 0, 10, 20, 30, 40, 50μg carbon disulfide), place them in 25mL colorimetric tubes, add diethylamine-ethanol solution (10g/L) to 10mL, and mix. Add 1mL of copper acetate-ethanol solution (0.5g/L) to each sample and standard tube, add ethanol to the scale, and mix. Use a 1cm colorimetric 294
cup and adjust the zero point with a zero tube, measure the absorbance at a wavelength of 400nm, and draw a standard curve for comparison. 4.6.5 Calculation of results
The content of carbon disulfide in the sample is calculated according to formula (5.AX1000
mxV./V.X1000
Where:
X is the content of carbon disulfide in the sample, in milligrams per kilogram (mg/kg); A is the mass of carbon disulfide in the absorption diluent for determination, in micrograms (μg); m
-mass of the sample, in grams (g);
is the total volume of the sample absorption diluent, in milliliters (mL); V is the volume of the sample absorption diluent for determination, in milliliters (mL). The calculation result shall retain two significant figures.
According to GB/T5009.11.
Operate according to GB/T5009.17.
4.9 BHC and DDT
Operate according to GB/T5009.19.
4.10 Aflatoxin B
Operate according to GB/T5009.22.
Operate according to GB/T5009.15.
Operate according to GB/T5009.18.
4.13 Datura seeds
4.13.1 Identification
GB/T5009.36——2003
(5)
Datura seeds are triangular or kidney-shaped, flat, with dots on the surface, brown or tan, some with wrinkled edges, light brown, 2mm~3mm wide, some larger, about 5mm~6mm. 4.13.2 Alkaloid colorimetric qualitative analysis
4.13.2.1 Principle
After extraction, the alkaloids such as atropine contained in the sample react with fuming nitric acid and potassium hydroxide solution to produce a color. 4.13.2.2 Reagents
Ammonia water (1+1).
4.13.2.2.1
4.13.2.2.2
Ether.
4.13.2.2.3
4.13.2.2.4
4.13.2.2.5
Hydrochloric acid (1+5).
Chloroform.
Anhydrous sodium sulfate.
Fuming nitric acid.
4.13.2.2.6
4.13.2.2.7
Potassium hydroxide-ethanol solution (100g/L). 4.13.2.3 Analysis steps
Put about 30 seeds of Datura in a mortar, soak them with ammonia water (1+1), soak for a while, grind them into a viscous state, grind them with ether three times, 10mL each time, combine the acetaldehyde and ether in a separatory funnel, add 10ml hydrochloric acid (1+5), shake and extract for 1min, separate the hydrochloric acid layer into another separatory funnel, add ammonia water (1+1) to make it alkaline, shake and extract with 10mL trichloromethane for 1min, extract again, combine the chloroform layers, dehydrate through 295
GB/T5009.36-—2003
anhydrous sodium sulfate, and concentrate to 0.5mL for use. Take 0.2mL of the test solution in a small evaporator III, evaporate the solvent, add 4 drops of fuming nitric acid to dissolve the residue, evaporate to dryness on a water bath, the residue turns yellow, and after cooling, add a few drops of potassium hydroxide-ethanol solution (100g/L), it turns purple, and then turns red. Atropine, scopolamine and scopolamine all have this reaction.
4.13.3 TLC qualitative analysis
4.13.3.1 Principle
After the atropine and other alkaloids contained in the sample are extracted, separated by thin layer, and then developed with a color developer and compared with the reference standard. 4.13.3.2 Reagents
4.13.3.2.1 Silica gel G thin layer plate: thickness 0.3mm~0.5mm, activated at 105℃ for 1h, put in a desiccator for use. 4.13.3.2.2 Developing solvent: methanol-ammonia water (200+3). 4.13.3.2.3 Color developer: Weigh 0.85g bismuth subnitrate, add 10mL glacial acetic acid, add 40mL water, dissolve. Take 5mL, add 5mL potassium iodide solution (4g potassium iodide dissolved in 5mL water), add 20mL glacial acetic acid, dilute with water to 100mL. 4.13.3.2.4 Atropine standard solution: Weigh 120.0mg atropine sulfate, dissolve in 10mL water, add ammonia water (1+1) to make it alkaline, extract twice with chloroform, 8mL each time, dehydrate the chloroform extract with a little anhydrous sodium sulfate, filter into a 20mL stoppered colorimetric tube, then wash the filter with a little chloroform, add the washing liquid into the colorimetric tube, add chloroform to 20mL, this solution is equivalent to 5.0mg atropine per milliliter.
4.13.3.2.5 Dongzhuo alkali standard solution: Weigh 145.0 mg Dongzhuo alkali hydrobromide, and treat the following in the same way as the atropine standard solution, making each milliliter equivalent to 5.0 mg Dongzhuo alkali. 4.13.3.3 Analysis steps
2 cm below the bottom of the thin layer plate, spot 10 μL of atropine and Dongzhuo alkali standard solution, 30 μL~100L of sample extract concentrate, with a spacing of 1.5 cm between each spot, and place in a developing tank saturated with a developing agent in advance. When the solvent front extends to 10 cm~15 cm, take it out, evaporate the developing agent, and spray the color developer to show orange-red spots for a positive reaction. 4.13.4 Quantification
Weigh 1000 g of grain, and detect no more than 5 Datura seeds from it. 4.14 Ergot
4.14.1 Identification
4.14.1.1 Morphology
Ergot is three or four blunt cylindrical strips, slightly curved, slightly narrow at both ends, 0.3cm~0.4cm long, 1mm7mm thick, black or purple-brown on the outside, with longitudinal grooves and transverse cracks, brittle, easy to break, blunt triangular cross section, dark purple edges, grayish white or purple-white center. 4.14.1.2 Tissue section
Soak ergot in water for 24 hours to make it swell, sandwich it between potatoes or radishes and fix it, cut it into small slices as thin as possible with a small scalpel, develop the color with methylene blue solution (1g/L), and observe it under a microscope. Its tissue is compact. 4.14.2 Qualitative analysis of ergochrome and ergot alkaloids 4.14.2.1 Reagents
Tartaric acid solution (20g/1).
4.14.2.1.1
4.14.2.1.2 Anhydrous ether.
4.14.2.1.31
Saturated sodium bicarbonate solution.
4. 14.2. 1.42
Ammonia water (1→1).
4.14.2.1.5
Chloroform.
p-Dimethylaminobenzaldehyde solution: Weigh 0.125g p-dimethylaminobenzaldehyde, add 100mL dilute sulfuric acid (65mL sulfuric acid 4.14.2. 1.6
slowly pour into 35mL water, mix well, and cool) to dissolve, then add 0.1mL ferric chloride solution (50g/L), mix well. 4.14.2.1.7 Sulfuric acid.
4.14.2.1.8 Anhydrous ethanol: No fluorescence when observed under ultraviolet light wavelength of 365nm. 296
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