Residue Degradation Of Common-used Suckercides In Tobacco And Deliver Rate Into Tobacco Smoke

Dlibutalin, flumetralin and pendimethalin were three suckercides commonly used in tobacco,which have increased the tobacco production and improved quality. However, as the addictedconsumption, tobacco with pesticides’ residues has proved negative to consumers’ health; and, as anexogenous hazardous material, the harm of tobacco also has attracted much attention. This purpose wasto study the degradation rates of three suckercides during plantation, flue-curing and storage process andthe transfer rate during smoking process, which can guide the control of pesticide residues in cigarettesand protect consumers’ health. A new method using GC with an ECD detector was developed to detectthe residue of dlibutalin, flumetralin and pendimethalin in tobacco. The degradation rates duringplantation, flue-curing, storage and smoking process were studied and analyzed based on the maximumresidue limits （MRLs）. In addition, rational use of these three suckercides were put forward.Main results were as follows:（1） A method was developed to detect residues of dlibutalin, flumetralin and pendimethalin intobacco leaves using GC with an ECD detector. Samples were extracted with acetonitrile and cleaned upby Florisil-SPE columns. Recoveries of these three suckercides at the spiked levels of0.01mg/kg to10mg/kg were in the range from85.54%to99.82%with the relative standard deviations（RSD） of1.83%to7.92%. The limit of detections were in the range of1.0×10^-114.3×10^-10mg/kg and the limit ofquantities were in the range from0.01mg/kg to0.05mg/kg. The method was precise and simple. It wasapplicable to determine the residues of dlibutalin, flumetralin and pendimethalin in fresh tobacco, drytobacco and cambridge filter.（2） Field degradation experimrnts were carried out at two locations in Qingdao, Shandong province,and Changsha, Hunan province during2010²011. The results suggested that the degradation of thesethree suckercides all followed the first-order degradation kinetics with the half-life values varying from2.1to5.9days for flumetralin,5.2to12.2days for dlibutalinand,3.3to5.2days for pendimethalin,respectively. The degradation of these three suckercides are fast during the field experiment and theybelong to easily degradable pesticides.（3） Original deposits of dlibutalin, flumetralin and pendimethalin in tobacco after applied at highconcentrations were1.82mg/kg to71.68mg/kg. The residues decreased to0.12mg/kg to12.99mg/kgafter curing，with degradation rates in the range64.11%to97.54%. The original deposit in tobacco leafreceiving low concentrations were1.32mg/kg to38.47mg/kg and decreased to0.13mg/kg to18.55mg/kg, with degradation rates61.29%to92.07%. The residues of these three suckercieds werereduced remarkably during curing process.（4） The effect of storage time on residue degradation was assessed in tobacco spiked with twoconcentrations （1.0mg/kg and10.0mg/kg） at six locations in different climate regions of China viz.,（1）Qingdao, Shandong province,（2） Hefei, Anhui province,（3） Yuxi,Yunnan province,（4） Fuzhou Fujianprovince,（5） Xuchang Henan province,（6） Wuhan Hubei province. The results suggest that the relationship between storage time and residue level proved to be negative. The half-lives ofpendimethalin, dlibutalin and flumetralin were173to495days,173to495days and216to533days,respectively. Therefore, the degradation of these three suckercides were slow under the commonstroring condition..（5） A method was developed to capture the production of cigarette smoking and detect the residuesof dlibutalin, flumetralin and pendimethalin in cigarette mainstream smoke during the smoking process.The transfer rates of dlibutalin, dlumetralin and pendimethalin in mainstream smoke were8.52%to14.58%,12.53%to13.30%and16.73%to21.04%, respectively.