The preparation of the test is very important before the measurement is carried out. The following describes the extraction and purification of organophosphorus pesticide residues in foods.
1 reagent
1.1 Dichloromethane.
1.2 anhydrous sodium sulfate.
1.3 5% sodium sulfate solution.
1.4 Acetone.
1.5 Neutral alumina: For chromatography, after activation at 300 ° C for 4 h, use.
1.6 Activated carbon: Weigh 20g of activated carbon and soak it in 3N hydrochloric acid overnight. After suction filtration, wash it with water until it is free of chloride ions, and dry at 120 °C for use.
2 instruments
2.1 Homogenizer
2.2 vertical oscillator
2.3 filter
2.4 HMS-350 Oscillator
3 method of operation
3.1 Vegetables: Add vegetables and diluents to a special sterile sample bag, put them into the homogenizer, close the door and start and complete the sample crushing and mixing. Weigh 10g of the mixed sample, place it in a 250ml conical flask, add 30-100g anhydrous sodium sulfate (according to the water content of the vegetable), dehydrate it, shake it vigorously with a vertical shaker, if there is solid sodium sulfate. , indicating that the addition of anhydrous sodium sulfate is enough. Add 0.2 to 0.8 g of activated carbon (according to vegetable pigment content) and decolorize. 70 ml of dichloromethane was added and shaken on a vertical shaker for 0.5 h, filtered through a filter paper using a filter. The filtrate was weighed in 35 ml, and naturally dried to near dryness in a fume hood at room temperature. The residue was washed several times with a small amount of dichloromethane, transferred to a 10 ml (or 5 ml) stoppered test tube, and made up to 2 ml, and set aside.
3.2 Rice: Shelling, grinding, passing through 20 mesh sieve, mixing. 10 g was weighed, placed in a stoppered Erlenmeyer flask, 0.5 g of neutral alumina, and 20 ml of dichloromethane were added, shaken on a vertical shaker for 0.5 h, filtered using a filter, and the filtrate was directly injected. If the pesticide residue is too low, add 30 ml of dichloromethane, shake and filter, and measure 15 ml of the filtrate to concentrate and dilute to 2 ml of injection.
3.3 Wheat, corn: The sample is ground through a 20 mesh sieve and mixed. 10 g of the flask was placed in a stoppered flask, 0.5 g of neutral alumina, 0.2 g of activated carbon and 20 ml of dichloromethane were added, and shaken on a vertical shaker for 0.5 h, filtered using a filter, and the filtrate was directly injected. If the pesticide residue is too low, add 30 ml of dichloromethane, shake and filter, and measure 15 ml of the filtrate to concentrate, and dilute to 2 ml of the injection.
3.4 Vegetable oil: Weigh 5g of the mixed sample, dissolve it in 50ml of acetone and wash it into the separatory funnel. After shaking, add 10ml of water and shake gently for 1min. After standing for more than 1h, discard the oil layer deposited below. The upper layer solution is poured into the other separatory funnel from the upper part of the separatory funnel. Be careful not to pour the remaining oil droplets (if the emulsion is severe and the layering is unclear, put it Into a 50 ml centrifuge tube, centrifuge with a HMS-350 shaker at 2500 r/min for 0.5 h, and aspirate the upper layer solution with a dropper. Add 30 ml of dichloromethane, 100 ml of 5% sodium sulfate solution, and shake for 1 min. After standing to separate the layers, the dichloromethane extract was transferred to an evaporating dish. The aqueous acetone solution was extracted once more with 10 ml of dichloromethane, and after layering, it was combined in an evaporating dish. After Natural evaporation, such as anhydrous, the residual liquid in the evaporating dish can be washed in a small amount with a small amount of methylene chloride into a measuring cylinder, and the volume is adjusted to 5 ml. Add 2g of anhydrous sodium sulfate to shake and dehydrate, add 1g of neutral alumina, 0.2g of activated carbon (0.5g of hair oil can be added), shake off and decolorize, filter, and directly inject the filtrate. After the methylene chloride extract is naturally volatilized, if there is a small amount of water, the volatilized residue can be washed into the small separatory funnel with 5 ml of dichloromethane, and extracted for 1 min. After standing and layering, the methylene chloride layer is separated into In a measuring cylinder, extract once with 5 ml of methylene chloride, combine into a measuring cylinder, dilute to 10 ml, add 5 g of anhydrous sodium sulfate, shake and dehydrate, add 1 g of neutral alumina, 0.2 g of activated carbon, shake Deoil and decolorize, filter, and directly inject the filtrate. Or pour methylene chloride and water together into a measuring cylinder, wash the evaporating dish with a small amount of dichloromethane, wash the liquid into a measuring cylinder, and adjust the volume to 5 ml with methylene chloride layer, add 3 g without Sodium sulfate in water is then legally operated as above with neutral alumina and activated carbon.
1 reagent
1.1 Dichloromethane.
1.2 anhydrous sodium sulfate.
1.3 5% sodium sulfate solution.
1.4 Acetone.
1.5 Neutral alumina: For chromatography, after activation at 300 ° C for 4 h, use.
1.6 Activated carbon: Weigh 20g of activated carbon and soak it in 3N hydrochloric acid overnight. After suction filtration, wash it with water until it is free of chloride ions, and dry at 120 °C for use.
2 instruments
2.1 Homogenizer
2.2 vertical oscillator
2.3 filter
2.4 HMS-350 Oscillator
3 method of operation
3.1 Vegetables: Add vegetables and diluents to a special sterile sample bag, put them into the homogenizer, close the door and start and complete the sample crushing and mixing. Weigh 10g of the mixed sample, place it in a 250ml conical flask, add 30-100g anhydrous sodium sulfate (according to the water content of the vegetable), dehydrate it, shake it vigorously with a vertical shaker, if there is solid sodium sulfate. , indicating that the addition of anhydrous sodium sulfate is enough. Add 0.2 to 0.8 g of activated carbon (according to vegetable pigment content) and decolorize. 70 ml of dichloromethane was added and shaken on a vertical shaker for 0.5 h, filtered through a filter paper using a filter. The filtrate was weighed in 35 ml, and naturally dried to near dryness in a fume hood at room temperature. The residue was washed several times with a small amount of dichloromethane, transferred to a 10 ml (or 5 ml) stoppered test tube, and made up to 2 ml, and set aside.
3.2 Rice: Shelling, grinding, passing through 20 mesh sieve, mixing. 10 g was weighed, placed in a stoppered Erlenmeyer flask, 0.5 g of neutral alumina, and 20 ml of dichloromethane were added, shaken on a vertical shaker for 0.5 h, filtered using a filter, and the filtrate was directly injected. If the pesticide residue is too low, add 30 ml of dichloromethane, shake and filter, and measure 15 ml of the filtrate to concentrate and dilute to 2 ml of injection.
3.3 Wheat, corn: The sample is ground through a 20 mesh sieve and mixed. 10 g of the flask was placed in a stoppered flask, 0.5 g of neutral alumina, 0.2 g of activated carbon and 20 ml of dichloromethane were added, and shaken on a vertical shaker for 0.5 h, filtered using a filter, and the filtrate was directly injected. If the pesticide residue is too low, add 30 ml of dichloromethane, shake and filter, and measure 15 ml of the filtrate to concentrate, and dilute to 2 ml of the injection.
3.4 Vegetable oil: Weigh 5g of the mixed sample, dissolve it in 50ml of acetone and wash it into the separatory funnel. After shaking, add 10ml of water and shake gently for 1min. After standing for more than 1h, discard the oil layer deposited below. The upper layer solution is poured into the other separatory funnel from the upper part of the separatory funnel. Be careful not to pour the remaining oil droplets (if the emulsion is severe and the layering is unclear, put it Into a 50 ml centrifuge tube, centrifuge with a HMS-350 shaker at 2500 r/min for 0.5 h, and aspirate the upper layer solution with a dropper. Add 30 ml of dichloromethane, 100 ml of 5% sodium sulfate solution, and shake for 1 min. After standing to separate the layers, the dichloromethane extract was transferred to an evaporating dish. The aqueous acetone solution was extracted once more with 10 ml of dichloromethane, and after layering, it was combined in an evaporating dish. After Natural evaporation, such as anhydrous, the residual liquid in the evaporating dish can be washed in a small amount with a small amount of methylene chloride into a measuring cylinder, and the volume is adjusted to 5 ml. Add 2g of anhydrous sodium sulfate to shake and dehydrate, add 1g of neutral alumina, 0.2g of activated carbon (0.5g of hair oil can be added), shake off and decolorize, filter, and directly inject the filtrate. After the methylene chloride extract is naturally volatilized, if there is a small amount of water, the volatilized residue can be washed into the small separatory funnel with 5 ml of dichloromethane, and extracted for 1 min. After standing and layering, the methylene chloride layer is separated into In a measuring cylinder, extract once with 5 ml of methylene chloride, combine into a measuring cylinder, dilute to 10 ml, add 5 g of anhydrous sodium sulfate, shake and dehydrate, add 1 g of neutral alumina, 0.2 g of activated carbon, shake Deoil and decolorize, filter, and directly inject the filtrate. Or pour methylene chloride and water together into a measuring cylinder, wash the evaporating dish with a small amount of dichloromethane, wash the liquid into a measuring cylinder, and adjust the volume to 5 ml with methylene chloride layer, add 3 g without Sodium sulfate in water is then legally operated as above with neutral alumina and activated carbon.
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