Study On Residue Trends Of Fipronil In Cabbage And Soil

Fipronil(5-amino-l-[2,6-dichloro-4-(trifluromethyl)phenyl]-4-[(trifluromethyl)sulfinyl-l H-pyrazole ], a phenylpyrazole insecticide, was discovered by Rhone-Poulenc Agro in 1987, introduced in 1993, and registered as a pesticide in the China 1996. At first, fipronil was formulated as roach or ant baits, flea and tick sprays for pets, and in granular turf products to control mole crickets; then fipronil is widely used to control agricultural insect. Fipronil is efficient to control larva of orthoptera, lepidoptera and coleoptea. Fipronil disrupts normal nerve function by targeting y -aminobutyric acid receptor of insects and blocking chlorine ion channels which adjusted by y -aminobutyric acid. Because toxicity of fipronil is low, and efficient to control pest, it was introduced to China ten years ago. But there were few reports on how to use fipronil safely. So we have to study the residue trend of fipronil in vegetable and teach the farmer how to use fipronil to control insect rightly.Firstly, a simple and efficient residue analytical method was developed for the analysis of fipronil, then study the residue dynamics of fipronil and its metabolites in cabbage and soil in different times. At last, degradation regularity of fipronil was studied under different temperature and different pH in lab. The results of the study are recounted as follows:1. Analytical method of fipronil and its metabolites1.1 A design of orthogonal conic substation of 3 factors and 2 levels was adopted to study the influence of condition of GC. The result showed the best condition of GC, inlet temperature: 250"C, oven temperature: 80℃(lmin)-30℃/min-200℃(5min)-40℃/min-250℃(3min), velocity of carrier gas: lmL/min, makeup: 60mL/min detector: 270℃, injection: luL. Under this conditions, the fipronil and its three metabolites was analyzed, all the four ingredients were completely separated. The separate degree between fipronil and MB45950 is 2. The calibration curves (0.01 to 2mg/kg) indicated that the relationships between peak area and injection amount of fipronil and its metabolites were more than 0.9999.1.2 A residue analytical method was developed for the analysis of fipronil in cabbage and soil. The fipronil and its metabolites were extracted with acetone. Firstly, the cabbage was immerged in acetone, homogenized. The soil was immerged in acetone and distilled water, vibrated for half an hour on ultrasonic vibrator. The extracts were re-extracted with dichloromethane by liquid-liquid separation and cleaned up by chromatography column filled with litmusless alumina, then evaporated to approximately dry, concentrated to a small volume with ethyl acetate. The concentrated extract was detected by gas chromatography with the electron capture detector. This method was rapid and efficient. The fortified average recoveries of this method varied from 86.77%~98.45%.