Objective  Due to the frequent occurrence of forest pests and diseases, a large number of chemical pesticides were used for pest control which enter the water and pollute the water resources. Therefore, it is planned to establish a novel sample pretreatment method for on-site processing to detect pesticides in environmental water bodies.

  Method  0.499 2 g of citric acid, 0.405 6 g of sodium dihydrogen phosphate, 0.218 4 g of sodium bicarbonate and 0.180 0 g of sodium caproate are weighed, ground and mixed evenly. The powder was compressed by a tablet machine into effervescent tablets for use. The polypropylene oil-absorbent cotton was cut into a cylinder with a height of 2 cm and a density of 60 mg/cm and packed into a filter column, and a novel homemade filter column was accomplished finally. The 10 mL sample was placed in a syringe and added with effervescent tablets. After the reaction was complete, it was filtered through a self-made filter column. After the filter column being eluted with 200 μL of acetonitrile, the filtrate was detected by gas chromatography-electron capture detector.

  Result  Under the optimal conditions, the linearity was in the concentration ranges of 5−500 μg/L, with coefficients greater than 0.999 0. The limit of detection and limit of quantification were calculated based on 3 times signal-to-noise ratio and 10 times signal-to-noise ratio. The limit of detection and the limit of quantitation were in the range of 0.22−1.88 μg/L and 0.75−6.25 μg/L. The recovery rate ranged between 88.2%−113.0%, the relative standard deviation was 0.8%−6.1%, and the enrichment factor was between 65−108.

  Conclusion  In this study, a new method named switchable hydrophilic solvent-based effervescent tablet assisted on-site dispersion liquid-liquid microextraction-gas chromatography was established to determine five pyrethroid pesticides in environmental waters. This method does not require the use of electrical equipment and can realize on-site pretreatment, which reduces the consumption of manpower and material resources and has broad application prospects.