Residues of four triazole fungicides in tobacco leaves under field condition and during curing

Residues of four triazole fungicides (triadimefon, myclobutanil, tebuconazole and difenoconazole) in tobacco leaves under field condition and during curing were investigated. Following extraction with acetonitrile, the samples were cleaned up by a Florisil solid phase extraction column, and then determined by gas chromatography-mass spectrometry in selected ion monitoring mode. The average recoveries of the four triazole fungicides were found in the range of 82.7-97.3% with relative standard deviations of 1.1-4.6% in green and cured tobacco leaves. The residues of triadimefon, myclobutanil, tebuconazole and difenoconazole in Shandong, Sichuan, Yunnan, Liaoning and Jiangxi were found in the range of 0.02-0.32mg/kg, 0.41-4.93mg/kg, 0.37-9.84mg/kg and 0.25-4.85mg/kg in cured tobacco leaves when measured 14days after the last application. The residue levels of the four triazole fungicides in most cured tobacco samples were lower than that in green tobacco samples, indicating that high temperature degradation surpassed dehydration concentration during the curing process.