Residue analysis experiments for organochlorine pesticides

Summary

Usually organochlorine pesticides (OCLs) are divided into DDT and its analogues, hexachlorohexane and cyclopentadienyl derivatives, which are not easy to be decomposed in the normal environment, and are easy to be enriched and accumulated in the fat of organisms through the food chain, and have a high degree of chemical stability, and their excessive use over a long period of time can easily lead to serious residual contamination and increase the resistance of pests. The presence of trace amounts of OCLs can be detected in air and water in many parts of the world.

(Source: Food safety monitoring technology / edited by Zhu Jian and Deng Xiaojun. (Beijing: Chemical Industry Press, 2006.8)

Operation method

Gas Chromatography-Electron Capture Detector (GC-ECD)

Materials and Instruments

Fruits Vegetables
Petroleum Ether-Acetone Petroleum Ether Sodium Sulfate Sodium Sulfate Anhydrous Florisil
Gas Chromatograph Triangular Flasks Pounders Brinell Funnels

Move

I. Extraction

The extraction of organochlorine pesticide residues in food has a variety of options depending on the matrix, available single solvent and mixed solvents, the means of extraction is useful for Soxhlet extraction, shock extraction, ultrasonic apparatus ultrasonic extraction, accelerated solvent extraction, microwave extraction and so on.

Second, purification

For the determination of only hexachloride, DDT and other acid-stabilized organochlorine pesticides, the most commonly used method is the use of concentrated sulfuric acid sulfonation, but for the simultaneous determination of organochlorine pesticides, such as Aldrin, Dieldrin and other organochlorine pesticides can not be used to use concentrated sulfuric acid sulfonation, is generally used in the column chromatography, the most widely reported is the Florisilica soil column chromatography, in the simultaneous determination of a variety of organochlorine pesticides, according to the specific pesticides determined, the use of In the simultaneous determination of a variety of organochlorine pesticides, according to the determination of specific pesticides, the use of different solvents.

Determination

In recent years, the determination of a variety of organochlorine pesticides by capillary chromatography has become a standard method in many countries and associations. Generally, non-polar to weakly polar capillary columns are commonly used for the determination of organochlorine pesticides.

Fruits and vegetables in a variety of organochlorine pesticide residues in the determination of capillary gas chromatography as an example:

Fruit and vegetable samples were placed in a tissue masher and mashed at high speed as test samples. The sample was weighed 20.00 g in a 250 mL stoppered triangular flask, 100 mL of petroleum ether-acetone (4+1) was added, and shaken for 30 min. Filtering was carried out through a Büchner funnel, the residue was washed with 2×20 mL of petroleum ether, and the filtrate was combined in 500 mL of a separatory funnel, and the acetone was removed by washing with 20 g/L of aqueous sodium sulfate solution (50 mL×2). The upper layer of petroleum ether was dehydrated with anhydrous sodium sulfate and collected in a 250 mL chicken-centered flask and concentrated on a rotary evaporator to about 5 mL. In a 2 cm I.D. x 25 cm glass column, a little glass wool was added to the bottom, and 1 cm of anhydrous sodium sulfate high, 5 g of Florisil, and 1 cm of anhydrous sodium sulfate were added sequentially. The column was first pre-washed with 40 mL of anhydrous ether-petroleum ether solution (15+85), and the leachate was discarded. The concentrated sample solution was transferred into the column, and the sample solution concentration vial was washed with 2×5 mL of petroleum ether and transferred into the column together. Finally, the column was eluted with 200 mL of anhydrous ethyl ether-petroleum ether solution of the above content, and all the eluates were collected and evaporated to about 40 mL with petroleum ether at 40 ℃ on a water bath under reduced pressure and condensed to 50 mL for chromatographic analysis. Measurement mode: select ion monitoring mode (SIM); injection mode: no shunt injection, open the shunt valve after 1.5 min; select monitoring ion (m/z).

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