| Sulfonylurea is new herbicides and used wildly in recent years. It is main kind of herbicides developing rapidly in latest years. Although the half-life of sulfonylureas in soil is not long and they have low harm to mammalian, their extremely high biochemical toxicity to plant appears during the application. One of the most serious problems is the harm to the subsequent crops. Therefore it is essential to determinate their residues in soil and water.HPTLC is fast, low cost, convenience and is always ready for using. It determinates most chemicals including pesticide. But it is seldom used in quantitative determination of sulfonylureas. Furthermore, although there are a few of articles on the method validation of GC and HPLC, it is seldom reported in pesticide analysis by HPTLC.In this study, the method of determining 5 sulfonylureas (metsulfuron- methyl, chlorsulfuron,bensulfuron- methyl, chlorimuron- ethyl, tribenuron- methyl) by HPTLC was established. Itincluded the qualifications of application, development and scan, the qualitative andquantificational parameters.The qualifications of application involved the amount, speed and bandwidth of application. Thelight, slit width, speed, optimizing optical system and scanning wavelength were included in thequalifications of scan. The mobile phases were optimized. The detective limits, quantitative limits,standard curves and their regression equation, and proposed working range were given inquantification.The stability of five sulfonylurea standards determinated by HPTLC was performenced. This is thepre-validation experiments and the first step in validation. The 5 sulfonylureas specificity wasvalidated by the forced degradation by acid, base, oxidizing agent, light and heat.The effects of environmental factors and developing methods on the chromatogram weredeveloped. This involved humidity, the vapor of mobile phases, the ascending and horizontaldevelopment.Using the established method, the bensulfuron- methyl residue in tap- water and the soil samplefortified by the mixture sulfonylureas (chlorsulfuron, bensulfuron- methyl, chlorimuron-ethyl) weredetermined. The water sample was extracted by SPE and the extract was determined withoutclean- up. The soil sample was determined after L-L extraction. The extraction was not necessaryto clean up, either. The purity of peak was demonstrated by the spectrum scan. The recoveries ofthe determination developed on HPTLC and TLC were compared with each other.The results were as follows:The qualification of application: Application speed is 4-7 s- L-1; pressure of N2 is 0.28 MPa,Application amount was 1-160ng for standards, 5-20 L for extraction of water and 50 L forextraction of soil respectively.The qualification of scan: Scan slit is 6.00 0.45 mm. Scan speed is 20 mm.s-1. The detector limitwas detected by light optimizing system, and the quantitative determination by resolutionoptimizing system. Scan wavelength for water sample is 201 nm, for soil, 237nm.The mobile phase A, chloroform + acetone + glacial acetic acid, 90+10+0.75, v/v/v, The mobilephase B, toluene + ethyl acetate; 50+50, v/v.Developing by MPA and MP B, The value of Rf of mesulfuron- methyl is 0.31-0.41, chlorsulfuron is0.21-0.44, bensulfuron- methyl is 0.38-0.65, chlorimuron- ethyl is 0.58-0.70, and tribenuron-methyl is 0.57-0.80.The detector limit is 2-10ng. The quantitative limit is 7-26ng. The proposed working rang is7-160ng. The regression coefficient r is 0.99884- 0.99988. The residual standard deviation of thestandard point sdv is 1.57-4.88%.The results of stability test indicated that the 5 sulfonylurean herbicides were stable during thedetective process by HPTLC without protective measurement. It was accepted according to ICH. Itwas not change when the degradation of standards subjected to acid, base, oxidizing agent, lightand heat was forced to perform.Developped by MP A, the effect of humidity on th... |
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