Predict Water Solubility of Quinclorac by Henderson-Hasselbalch Equation under Different pH Solutions
Predict Water Solubility of Quinclorac by Henderson-Hasselbalch Equation under Different pH Solutions
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利用 Henderson-Hasselbalch 方程预测不同 pH 溶液下二氯喹啉酸的水溶性
DOI：
10.14233/ajchem.2016.19406
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发表时间：
2016
影响因子：
--
通讯作者：
Lianyang Bai
中科院分区：
文献类型：
--
作者：
Aixing Mao;Kailin liu;Xiangying Liu;Lianyang Bai
农药溶解度是影响农药制剂制备、环境行为、残留提取和应用的重要分子物理化学参数之一，因此农药溶解度信息在农药研究和应用中至关重要。随着合成农药的增加，大部分农药特别是除草剂是可电离的[1]。由于水溶性较高且依赖于pH值，可电离农药在世界范围内的地下水和地表沃茨中经常被发现。二氯喹啉酸是一种取代喹啉羧酸类除草剂，是一类选择性很强的生长素类除草剂，已被广泛应用于水稻田杂草的防除。然而，在许多文献中发现二氯喹啉酸的溶解度不同。据报道，二氯喹啉酸在水中的溶解度为62 mg/L [2，3]、0.065 mg/L [4，5]、0.065 mg/kg（pH 7水）[4]、64 mg/L [6]，在20 °C和pH 5.5时在水中的溶解度为72 mg/L（去离子水），75.9 g/L，20 °C，pH 10.3（NaOH，0.1Mol/L）[7]等。为什么报告的溶解度不同？哪一个是可靠的？二氯喹啉酸是一种可电离的除草剂（弱酸），在20 °C时pKa = 4.34。根据溶液的pH，可电离化合物可以以中性（不带电）或电离（带电）形式存在。它们在荷电溶液中的溶解度较高。用Henderson-Hasselbalch方程预测二氯喹啉酸在不同pH溶液中的溶解度
Solubility is one of the most important molecular physicochemical parameters that influence the formulation preparation, environmental behaviour, residue extraction and application of pesticide, so the information of pesticide solubility is essential in pesticide research and application. With the increase of synthetic pesticide, a large fraction of the pesticide especially herbicide is ionizable [1]. Since the water solubility are higher and depend on pH, the ionizable pesticides are frequently found in groundwater and surface waters worldwide. Quinclorac is a substituted quinoline carboxylic acid, a class of highly selective auxin herbicides and have been used to control weed in paddy field. However, the solubility of quinclorac was found different in many papers. The solubility of quinclorac in water was reported as 62 mg/L [2,3], 0.065 mg/L [4,5], 0.065 mg/kg at pH 7 water [4], 64 mg/L [6], Solubility in water 72 mg/L at 20 °C at pH 5.5 (deionized water), 75.9 g/L at 20 °C at pH 10.3 (NaOH, 0.1Mol/L) [7], etc. Why the reported solubility was different? Which one is reliable? The quinclorac is an ionizable herbicide (weak acid), with pKa = 4.34 at 20 °C. The ionizable compound can exist in neutral (uncharged) or ionized (charged) form depending on the pH of the solution. They are more soluble in charged Predict Water Solubility of Quinclorac by Henderson-Hasselbalch Equation under Different pH Solutions