体系pH值、乳化温度和电解质离子对异丙甲草胺水乳剂稳定性的影响

通过测定药物液滴的平均粒径和Zeta电位研究了体系pH值、 乳化温度和电解质离子对乳化剂三苯乙烯基苯酚聚氧乙烯醚磷酸酯三乙醇胺盐(SCP)稳定的异丙甲草胺水乳剂稳定性的影响. 结果发现, 体系的pH值影响SCP分子在水中的电离能力, 当pH=9时, SCP完全电离, 能为液滴提供较大的静电稳定作用, 水乳剂稳定性最好; 乳化温度低时, SCP分子向液滴界面扩散慢, 且舒展不完全, 液滴所带负电荷较少, 水乳剂稳定性差; 温度升高后, 水相黏度减小, 布朗运动加剧, 液滴碰撞合并几率增大, 且SCP分子热运动增强, 易从界面逃逸, 液滴间静电斥力减弱, 同时SCP亲水性下降, 水乳剂稳定性变差; 电解质离子会压缩界面双电层, 降低Zeta电位, 液滴带电量减少而聚结, 离子浓度越大, 电荷数越大, 水乳剂稳定性越差. 在相同的离子浓度下, 水合半径小的Ca²⁺压缩双电层能力强于Mg²⁺, 添加Ca²⁺后水乳剂稳定性更差.

Effects of pH Value,Emulsification Temperature and Electrolytical Ions on the Stability of Metolachlor Emulsion in Water

The effects of pH value, emulsification temperature and electrolytical ions on the the stability of metolachlor emulsion in water which was stabilized by emulsifier triethanolamine tristyryiphenol polyoxyethy-lene ether phosphate (SCP) were studied by means of average size analysis and Zeta potential measurement. It has been found that: pH value affected the ionization of SCP in water, at pH=9, the stability of emulsion in water was best on account of strong electrostatic exclusion which was provided by completely ionizing of the molecules; when the emulsification temperature was lower, the stability of the emulsion in water was poor because of the slow strength of interfacial film and the less negative charge of the droplets, which was due to the slow diffusion of SCP moleculars to the oil-water interface and the incomplete stretch of SCP moleculars; with the emulsification temperature rising, the viscosity of water phase decreased and the Brownian motion of the droplets were enhanced, which led to the increased probability of the droplets coalescence, and the SCP moleculars were easier to escape from the interface because of thermal motion, which caused the weaken electrostatic repulsion between the droplets, what was more, the hydrophile of SCP would decrease, therefore the stability of emulsion in water became worse;electrolytical ions were able to decrease Zeta potential by compre- ssing the electronic double layer thickness of droplets interface, which could lead to droplets aggregation due to the reduction of electric quantity, the higher the concentration of electrolytical ions and charge number were, the worse the stability of metolachlor emulsion in water were, and ultimately made the the stability of emulsion in water worse. If the electrolytical ions concentration were the same, the capacity of compressing the electro-nic double layer thickness of droplets interface by Ca2+ was stronger than Mg2+, the stability of metolachlor emulsion were worse after adding Ca2+.