Study On Detection And Degradation Of Defoliant On Cotton Fiber

Defoliant can promote cotton boll opening and have most of the leaves abscised beforeharvesting time, thereby improving operation efficiency of mechanical harvest and decreasingpercentage of trash content in raw cotton. The use of defoliant had the potential hazards to thesafety of textile workers and consumers of cotton productions. We import a lot of cotton fiberfrom foreign countries every year, while these countries spray defoliant in cotton cultivationstage widely. So the problem of defoliant residual is worth our attention. At present, there isno standard detection method and limitation of defoliant on cotton fiber. So it is necessary tobuild detection methods and study the attenuation characteristics of defoliant on cotton fiber.Among various defoliant, this paper chose thidiazuron and tribuphos as research objects,which were commonly used.In this paper, thidiazuron was analyzed using UV-spectrometer. The results showed that,there were three characteristic absorption peaks exhibited at228,243and279nm ofthidiazuron in acetonitrile. The absorbance at279nm，which had higher sensitivity and smallerinterference, was used for quantitative analysis of thidiazuron. Thidizauron degraded on cottonfiber when exposed to UV lamp, and the photolysis of thidiazuron fit the first-order kineticswell, and the photolytic rate increased with the increase of temperature. Aniline and Phenylisocyanate were identified as photolytic product of thidiazuron by use of GC-MS. Theactivation energy of photolysis was17.08kJ·mol^-1.Scouring process was important in the production of cotton fabrics. In this process,thidiazuron shifted from cotton fiber to the scouring solution （NaOH solution）, which wassafety for cotton fabrics, while harmful to the solution and environment. The hydrolysis ofthidiazuron in NaOH solution and hot aqueous solution was also studied. In these twosolutions, with the increase of temperature, the hydrolytic rate of thidiazuron both increased.Compared with aqueous solution, NaOH solution may facilitate its hydrolysis. The activationenergy of hydrolysis was85.08kJ·mol^-1and15.9kJ·mol-1respectively in hot aqueous solutionand sodium hydroxide solution. Tribuphos was analyzed by gas chromatography/mass spectrometry （GC/MS）. Thismethod was sensitive，rapid with high recovery, which could be used for the determination oftribuphos of cotton fiber. With this method, we detected that under the effect of UV light,tribuphos degraded on cotton fiber, and with the increase of temperature, the photolytic rate oftribuphos increased. Tribuphos can be removed from cotton fiber after scouring. In hotaqueous solution, tribuphos kept stable, but degraded in sodium hydroxide solution. Thehydrolytic product of tribuphos was PO₄^3-. The hydrolysis of tribuphos was studied byammonium molybdate spectrophotometric method. The hydrolytic rate of tribuphos changedsignificantly due to the effect of concentration of sodium hydroxide solution and temperature.