In recent years, China has made great progress in the series of determination of various pesticide residues, and has issued four national standard methods. For example, GB/T 19648-2005, Method for Determination of 446 Pesticide Multi-residues in Fruits and Vegetables. Source: Food Safety Monitoring Technology (Chemical Industry Press)

Operation method

Gas Chromatography Mass Spectrometry

Materials and Instruments

Apple juice
Dichloromethane-hexane Distilled water
Beaker, glass rod, diatomaceous earth column, gas chromatograph.

Move

1. Pre-processing

Accurately weigh 50.0 g of apple juice concentrate in a 250 mL beaker, accurately add an equal amount of distilled water for dilution, stir well with a clean glass rod, accurately aspirate 20 mL of the diluted sample solution onto a diatomaceous earth column, and after all the liquid was fed into the column, continue to let it stand for 20 min, and then rinse the sample with dichloromethane-hexane (1:1, v/v/v) at a flow rate of 160 mL, and collect the effluent in a 200 mL concentration flask, concentrate it in a 40°C water bath until nearly dry, and then fix it accurately with hexane to 1 mL for gas chromatography detection. The flow rate was controlled to be 5 mL/min, and the effluent was collected in a 200 mL concentration flask, concentrated to near dryness in a water bath at 40°C, and then accurately diluted to 1 mL with hexane for detection by gas chromatograph.

2. Gas chromatographic conditions

Carrier gas: helium (99.999%)

Column flow rate: 1 mL/min

Inlet temperature: 250 ℃

Injection mode: pulse split injection; injection volume 1uL

Column temperature program: initial temperature 80 ℃, hold for 1 min, warm up to 160 ℃ at the rate of 10 ℃ / min, hold for 5 min, warm up to 240 ℃ at the rate of 3 ℃ / min, then warm up to 280 ℃ at the rate of 25 ℃ / min, hold for 10 min.

3. Mass spectrometry conditions

Interface temperature: 280 °C

Ion source temperature: 230 ℃

Quadrupole temperature: 150 ℃

Ionization method: EI Electron energy: 70 eV

Mass spectrometry detection method: Selected Ion Detection (SIM).

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