Division of Agricultural Chemicals, Indian Agricultural Research Institute, New Delhi, India.
J Environ Sci Health B. 2013;48(4):266-71. doi: 10.1080/03601234.2013.743761.
Pyrazosulfuron-ethyl, a new herbicide belonging to the sulfonylurea group, is used for weed control in rice crops growing in areas varying from acidic to alkaline soils. This study was undertaken to determine the degradation behaviour of pyrazosulfuron-ethyl in distilled water and buffer solutions at pH 4, 7 and 9. Degradation was pH-dependent and herbicide was least persistent in acidic pH followed by alkaline and neutral pH. The half-life of pyrazosulfuron-ethyl varied from 2.6 days (pH 4) to 19.4 days (pH 7) and half-life in distilled water was comparable to half-life at pH 7 buffer. HPLC analysis of different pH samples showed the formation of three metabolites viz., 5-(aminosulfonyl)-1-methyl-1H-pyrazole-4-carboxylic acid; ethyl 5-(aminosulfonyl)-1-methyl-1H-pyrazole-4-carboxylate and 2-amino-4,6-dimethoxy pyrimidine. The formation of pyrazosulfuron acid [5-([([(4,6-dimethoxy-2 pyrimidinyl)-amino]-carbonyl) amino]-sulfonyl)-1-methyl-1H-pyrazole-4-carboxylic acid] was not observed at any pH. The study indicated that the herbicide was least stable under acidic conditions and the predominant degradation route of pyrazosulfuron-ethyl in water is hydrolysis of sulfonamide linkage.
吡唑磺隆-乙基，一种新型磺酰脲类除草剂，用于在从酸性到碱性土壤的不同地区生长的水稻作物中除草。本研究旨在确定吡唑磺隆-乙基在蒸馏水中和 pH 值为 4、7 和 9 的缓冲溶液中的降解行为。降解行为依赖于 pH 值，在酸性 pH 值下，除草剂的持久性最低，其次是碱性和中性 pH 值。吡唑磺隆-乙基的半衰期在 2.6 天（pH 4）至 19.4 天（pH 7）之间变化，在蒸馏水中的半衰期与在 pH 7 缓冲液中的半衰期相当。不同 pH 值样品的 HPLC 分析表明形成了三种代谢物，即 5-（氨基磺酰基）-1-甲基-1H-吡唑-4-羧酸；乙基 5-（氨基磺酰基）-1-甲基-1H-吡唑-4-羧酸和 2-氨基-4,6-二甲氧基嘧啶。在任何 pH 值下均未观察到吡唑磺隆酸[5-([([(4,6-二甲氧基-2 嘧啶基)-氨基]-羰基)氨基]-磺酰基）-1-甲基-1H-吡唑-4-羧酸]的形成。研究表明，在酸性条件下，除草剂的稳定性最低，吡唑磺隆-乙基在水中的主要降解途径是磺酰胺键的水解。
