Donbrow M, Azaz E, Pillersdorf A
J Pharm Sci. 1978 Dec;67(12):1676-81. doi: 10.1002/jps.2600671211.
Aqueous solutions of polysorbate 20 undergo autoxidation on storage, with the peroxide number increasing and subsequently decreasing again, the acidity increasing continuously, the pH and surface tension falling and tending to level off, and the cloud point dropping sharply until turbidity begins at room temperature. The changes are accelerated by light, elevation of temperature, and a copper sulfate catalyst. At the same time, hydrolysis occurs, liberating lauric acid. Analysis of the alterations in these properties leads to the conclusion that hydrolysis has the major influence near room temperature and that oxyethylene undergoes chain shortening at temperatures above 40 degrees. However, evidence of degradation is detectable even in previously unopened commercial samples of polysorbates 20, 40, and 60, warranting attention to the stability of and standards for these surfactants as compared with the solid alkyl ether type of nonionic surfactant.
聚山梨醇酯20的水溶液在储存过程中会发生自动氧化，过氧化物值先升高后又降低，酸度持续增加，pH值和表面张力下降并趋于平稳，浊点急剧下降，直至在室温下开始出现浑浊。光照、温度升高和硫酸铜催化剂会加速这些变化。与此同时，会发生水解反应，释放出月桂酸。对这些性质变化的分析得出结论，在室温附近水解起主要作用，而在40摄氏度以上的温度下，氧化乙烯会发生链长缩短。然而，即使在之前未开封的聚山梨醇酯20、40和60商业样品中也能检测到降解迹象，因此与固体烷基醚型非离子表面活性剂相比，需要关注这些表面活性剂的稳定性和标准。
