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KT2520K26000DCW28QAS imported spot
Export
honey
Medium insecticidal residue test method
Chromatography
1
Subject content and scope of application
This standard specifies the export honey sampling, sample preparation, and gas chromatographic determination of pesticide residues. It applies to the testing of residual amounts of insecticides in exported honey.
2
Sampling and sample preparation
2.1
Inspection lot
Not more than 1000 pieces make up an inspection lot. Goods in the same inspection lot should have the same characteristics, such as packaging, marking, origin, specifications, and grades.
2.2
Number of samples
Batch (pieces): Minimum number of samples (pieces)
50 within: 5
50 ~ 100: 10
101 ~ 500: Every increase of 100, take 5
501 and above: Each increase of 100, take 2
2.3
Sampling tool
2.3.1
Sampling tube: stainless steel, 115 cm long, diameter about 2.5 cm.
2.3.2
Mixer: enamel bucket (or cup).
2.3.3
Single set of rods: stainless steel.
2.3.4
Vial bottle: 500mL frosted glass bottle.
2.4
Sampling method
According to 2.2, randomly extract the specified number of samples. Open one by one. Insert the sampling tube slowly, draw the sample. If the honey is crystallized, use the single rod to collect the sample. Each sample must be no less than 100g as the original sample. Pour into the sampler, mix evenly, load into a clean, dry vial, seal it, mark it, and send it to the laboratory promptly.
2.5
Sample preparation
Stir uncrystallized samples evenly. For samples with crystal precipitation, cap and stopper them. Place them in a water bath at no more than 60°C until fully melted and mixed. Cool quickly to room temperature. Be careful not to let moisture evaporate during melting. Store the prepared sample in a vial, seal it, and mark it.
2.6
Sample storage
The sample was stored at room temperature. Note: During sampling and sample preparation, contamination or changes in residue levels must be avoided.
3
Test methods
3.1
Method summary
Residual insecticides in honey are extracted using acetone sodium hydroxide solution with n-hexane. After purification via alkali-n-hexane and acid-n-hexane liquid-liquid partitioning, the sample is analyzed by gas chromatography with a nitrogen-phosphorus detector, using diphenylamine as an internal standard for quantification.
3.2
Reagents and materials
Unless otherwise stated, reagents are analytical grade, and water is distilled or deionized.
3.2.1
Acetone: heavy distillation.
3.2.2
N-hexane: heavy distillation with alkali.
3.2.3
Sodium hydroxide solution: 1 mol/L.
3.2.4
Sodium hydroxide solution: 0.5 mol/L.
3.2.5
Hydrochloric acid solution: 0.1 mol/L.
3.2.6
Internal standard solution: diphenylamine in n-hexane, 0.500 μg/mL.
3.2.7
Insecticide standard: purity > 99%.
3.2.8
Standard solution preparation: weigh approximately 40.0 mg of insecticide standard, accurately to 0.1 mg, dissolve in a 100 mL volumetric flask with n-hexane to prepare a stock solution of 0.400 mg/mL. Dilute quantitatively with n-hexane and add diphenylamine as an internal standard to prepare a working solution. The concentration of insecticide is about 0.200 μg/mL or similar to that in the sample solution, while diphenylamine is about 0.500 μg/mL. Prepare freshly.
3.3
Instruments and equipment
3.3.1
Gas chromatograph with nitrogen-phosphorus detector.
3.3.2
Integrator or recorder.
3.3.3
Rotatory evaporator.
3.3.4
Micro syringe: 10 μL.
3.4
Measuring step
3.4.1
Extraction
Weigh 20 g of sample, accurate to 0.1 g, in a 100 mL beaker. Add 30 mL of 1 mol/L sodium hydroxide solution, stir and dissolve, then add 50 mL acetone and pour into a 250 mL separating funnel. Wash the beaker twice with a few mL of acetone and add to the funnel. Then add 50 mL n-hexane, shake violently for 2 minutes. Let stand, retain the upper n-hexane layer, discard the lower and intermediate layers.
3.4.2
Purification
The n-hexane solution is washed once with 30 mL and 20 mL of 0.5 mol/L sodium hydroxide solution, discard the wash. Add 20 mL of 0.1 mol/L hydrochloric acid, shake for 2 minutes, let stand, transfer the lower hydrochloric acid layer to another 250 mL separating funnel. Add 10 mL of 0.1 mol/L HCl, shake, let stand, combine the hydrochloric acid solutions, discard the n-hexane layer. Add 30 mL of 1 mol/L NaOH and 60 mL of n-hexane, shake for 2 minutes, let stand, discard the aqueous layer. Transfer the hexane solution to a rotary evaporator flask, wash the funnel twice with a few mL of n-hexane, combine the washings. Concentrate under reduced pressure at 45°C until near dryness. Dissolve the residue with 1.00 mL of 0.500 μg/mL diphenylamine-n-hexane solution and analyze by gas chromatography.
3.4.3
Determination
3.4.3.1
Chromatographic conditions
a. Column: glass column, 2 m × 3 mm (i.d.), filled with 6% SE-54 on Chromosorb WHP (80–100 mesh), or 15% SE-30 on Chromosorb WHP (80–100 mesh) plus 0.6% KOH; b. Nitrogen: ≥99.99%, 60 mL/min; c. Hydrogen: 2.5 mL/min; d. Air: 170 mL/min; e. Column temperature: 198°C; f. Injection temperature: 250°C; g. Detector temperature: 250°C; h. Bead voltage: 6.8×2V.
3.4.3.2
Chromatographic determination
Inject 2 μL of standard working solution and sample solution into the gas chromatograph. Peak retention time: diphenylamine ≈ 3.8 min, insecticide ≈ 4.4 min.
3.4.4
Blank test
Perform the measurement procedure without adding any sample.
3.5
Calculation and representation of results
Use the chromatographic data processor to calculate using the internal standard method or the following formula:
Cs·A·Asi·mi
X=────────-
Csi·Ai·As·m
Where:
- X: Insecticide content in honey, mg/kg
- Cs: Insecticide concentration in standard working fluid, μg/mL
- Csi: Diphenylamine concentration in standard working fluid, μg/mL
- A: Peak area of insecticide in sample solution, mm²
- Ai: Peak area of diphenylamine in sample solution, mm²
- As: Peak area of insecticide in standard working fluid, mm²
- Asi: Peak area of diphenylamine in standard working fluid, mm²
- Mi: Total amount of diphenylamine added in sample solution, μg
- M: Total sample mass, g
Note: The calculated result must deduct the blank value.
4
Method for determining lower limit and recovery rate
4.1
Measuring the lower limit
The lower limit of the method is 0.005 mg/kg.
4.2
Recovery rate
Recovery rate experimental data: in the range of 0.005~0.100 mg/kg, the recovery rate is 89.8%~100.5%.
Additional information:
This standard was proposed by the State Import and Export Commodity Inspection Bureau of the People's Republic of China.
This standard was drafted by the Shanghai Import and Export Commodity Inspection Bureau of the People's Republic of China.
The main drafters of this standard are Ge Xiuli and Cai Zeci.
Main reference: Dr. Wiertz, Kurzer Abri β der Methode-Chlordimeformin Honig.
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