Determination of organochlorine pesticide residues of pyrethroids and polychlorinated biphenyls (PCBs) in brown rice in an experiment

Summary

Due to the requirement to detect more and more pesticide species, the limit is getting lower and lower, multi-residue detection technology has become the mainstream of pesticide residue analysis technology in food. Source: Food Safety Monitoring Technology (Chemical Industry Press)

Operation method

Gel Permeation Chromatography and Solid Phase Extraction Cleanup Technology

Materials and Instruments

Brown rice
Anhydrous sodium sulfate Ethyl acetate Nitrogen Dichloromethane-hexane
Gel Chromatography Columns Environed GPC Purification Pre-columns Purification Columns Two Quantitation Rings Waters 510 Liquid Chromatography Pumps 486 Ultraviolet Absorption Detector

Move

1. Extraction 5.0 g of sample was accurately weighed into a 200 mL centrifuge tube; 40 mL of ethyl acetate and 2 g of anhydrous sodium sulfate were added, homogenized three times for 1 min each, and the homogenization head was rinsed with 1O mL of ethyl acetate, and the rinses were combined. Centrifuge (2500 r/ min; 15 min; 25 ℃) to collect the upper layer of clarified liquid. The lower precipitate was added with 40 mL of ethyl acetate, and the homogenization and centrifugation process was repeated. The combined upper clarified solution was rotary evaporated to near dryness and blown dry under nitrogen. Dichloromethane-hexane (1 + 1) was transferred to a 10 mL centrifuge tube, and the volume of the solution was fixed to 6 mL. High-speed centrifugation was performed (3000 r/ min; 5 min). 2. Purification GPC device: Equipped with Environed GPC clean-up pre-column 150 mm×19 mm, clean-up column 300 mm×19 mm, two 2.4 mL quantitative rings, Waters 510 liquid chromatography pump, 486 ultraviolet absorption detector. The gel column was packed with Bio-Beads SX3 200-400 mesh. 4.8 mL of the upper clarified solution was injected into the GPC, and a gradient elution was performed by adding 3 mL of n-hexane, 5 mL of ethyl acetate-hexane (5 + 95), 5 mL of ethyl acetate-hexane (20 + 80), and 2 times of the elution solution, and the elution rate was controlled to be 1 mL/min. 90 mL of the mobile phase was collected after 11.5 min, and then the mobile phase was concentrated by rotary evaporation (80 r/min, 40C) to near dryness, and then blown with nitrogen. ) to near dryness and blown dry with nitrogen. The sample solution was made up to 1 mL with hexane. The Florigold column (6 mL/1000 mg) was pre-washed with 5 mL of ethyl acetate-hexane (20 + 80), 5 mL of ethyl acetate-hexane (5 + 95) and 5 mL of hexane. Take 0.5 mL of the spare sample solution over a Florisil soil column and discard the effluent. Add 3 mL of hexane, 5 mL of ethyl acetate-hexane (5 + 95) once and 5 mL of ethyl acetate-hexane (20 + 80) twice, and control the washing rate at 1 mL/min. 15 mL of the washing solution was collected, and the sample was rotary evaporated (80 r/min, 40 ℃) to near dryness, and then blown dry with nitrogen. The solution was fixed with n-hexane to 1 mL and detected by GC/ECD.

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