Stability of Photolysis and Hydrolysis of Prallethrin

The photolysis and hydrolysis of prallethrin was studied in the laboratory. The result of the test showed that the photolysis reaction of prallethrin in aqueous solutions irradiated by 500w xenon lamp fitted to the first order dynamic equation. The results also showed that the hydrolysis rate of prallethrin in buffer solutions with pH values of 5 in 25C were very slow. The rising temperature and pH values could both accelearate the hyrolysis. And discussion was also conducted to the mechanism of hydrolysis. KEYWORD: Prallethrin; Photolysis; Hydrolysis; Gas Chromatography International Conference on Industrial Technology and Management Science (ITMS 2015) © 2015. The authors Published by Atlantis Press 1752 was used as the light source, and quartz cold well was used to surround the lamp, which could run through the condensed water to keep the stability of the temperature inside the reactor. The photolysis reaction tube was quartz tube, which was 70 mm away from the light source, and the light intensity was 1.05×10 4 Lux. Water samples were taken regularly during the test to determine the changes of the pesticide concentration. During the photolysis test period, any other light resources should be isolated from the photolysis to reduce the influences on the test results. The spectral signature of the xenon lamp used in the test was similar to that of the sunlight (Fig.1), which could ensure that the artificial simulated light degradation conditions were as close to the natural conditions as possible. Fig. 1 The comparison between spectra of xenon lamp and spectra of the sunlight 1.2.5 Analysis of pesticide residues Water extraction: 10mL of water sample was taken and put in the separatory funnel, which was added with 20mL×2 petroleum ether, and after organic phase combination, the rotary evaporator was used to evaporate and concentrate the sample into a certain volume for gas chromatography. The recovery rate of pyrethroids at different pH buffer solutions was 93.4 100%, which showed a 3.03-10% deviation to the standard. Conditions of determination by gas chromatogra phy were as follows: Shimadzu GC-14B gas chromatograph and electron capture detector were used for the gas chromatography. Chromatographic column: the fused silica capillary column with 5% phenyl methyl silicone as the stationary phase and HP-5 length of 30m, diameter of 0.25mm and film thickness of 0.25m. Fig. 2 GC Temperature conditions: column temperature of 220C, vaporizing chamber of 250C, detecting chamber of 250 C. Gas flow rate: nitrogen of 40mL/min. Sample size: 1L. The concentration of pralle thrin standard solution: 25g/mL, as Figure 2 shows. 2 RESULTS AND DISCUSSION 2.1 Hydrolysis characteristics prallethrin The hydrolysis rate of pesticide was subjected to the influence of pesticide properties and water environment conditions, and the hydrolysis of pesticide in buffer solution system was fitted to the first order dynamic equation, which could be expressed using the following formula: