Schott H, Royce A E
J Pharm Sci. 1983 Dec;72(12):1427-36. doi: 10.1002/jps.2600721216.
Electrolytes often break emulsions to which they were added as active ingredients, adjuvants, or impurities. The stability of oil-in-water emulsions containing octoxynol 9 NF as the emulsifier and various added electrolytes was investigated by measuring droplet size, turbidity, and oil separation on storage at various temperatures and in a centrifugal field at 25 degrees. Electrolytes were added to hexadecane emulsions after emulsification (direct addition); alternatively, hexadecane was emulsified in octoxynol 9-electrolyte mixtures (reverse addition). Xylene emulsions were prepared by direct addition only. Hexadecane emulsions containing 0.10% octoxynol 9 were considerably more stable than xylene emulsions containing 0.60% because the surfactant is practically insoluble in hexadecane, but miscible in all proportions with xylene. An emulsifier soluble in the disperse phase as well as the continuous phase evidently forms less stable interfacial films. The electrolytes investigated were sulfuric and hydrochloric acids, magnesium nitrate, and aluminum nitrate, which salt octoxynol 9 in by complexation between its ether groups and their cations; sodium thiocyanate, which salts the surfactant in by destructuring water; and sodium chloride and sodium sulfate, which salt octoxynol 9 out. The addition of these electrolytes at concentrations up to 2 or 3 m to hexadecane emulsions produced fast and extensive creaming, little or no flocculation, no coalescence, and only minor changes in droplet size or turbidity on storage at room temperature. The extent of coalescence during centrifugation was actually reduced by the additives. Such stability is unusual. Droplet size and turbidity depended mainly on octoxynol 9 concentration. The greatest decrease in the former and increase in the latter occurred when the concentration was increased from 0.10 to approximately 0.4%. All emulsions became slightly coarser on storage at 25 degrees. Stability at 50 degrees was impaired by aluminum nitrate and magnesium nitrate and to a lesser extent by sodium sulfate and sodium chloride. Reverse-addition emulsions differentiated better between the electrolytes than direct-addition emulsions. Electrolytes salting octoxynol 9 in, especially by complexation, generally produced the finest and most stable emulsions. Similarly, xylene emulsions were destabilized more by the electrolytes which salted the emulsifier out than by those salting it in. Centrifugation of hexadecane emulsions at 7800 X g compressed the creamed emulsion layer into a plug of clear, transparent, isotropic gel from which coalesced hexadecane separated slowly on further centrifugation.(ABSTRACT TRUNCATED AT 400 WORDS)
电解质常常会破坏那些作为活性成分、佐剂或杂质添加到其中的乳液。通过在不同温度下储存以及在25℃的离心场中测量液滴大小、浊度和油相分离情况，研究了以辛基酚聚氧乙烯醚9 NF作为乳化剂并添加了各种电解质的水包油乳液的稳定性。乳化后将电解质添加到十六烷乳液中（直接添加）；或者，将十六烷在辛基酚聚氧乙烯醚9 -电解质混合物中乳化（反向添加）。二甲苯乳液仅通过直接添加制备。含有0.10%辛基酚聚氧乙烯醚9的十六烷乳液比含有0.60%的二甲苯乳液稳定得多，因为该表面活性剂实际上不溶于十六烷，但能与二甲苯以任意比例混溶。一种既溶于分散相又溶于连续相的乳化剂显然形成的界面膜稳定性较差。所研究的电解质有硫酸、盐酸、硝酸镁和硝酸铝，它们通过其醚基与阳离子之间的络合作用使辛基酚聚氧乙烯醚9盐析；硫氰酸钠，它通过破坏水使表面活性剂盐析；以及氯化钠和硫酸钠，它们使辛基酚聚氧乙烯醚9盐析出来。在十六烷乳液中添加浓度高达2或3 m的这些电解质，在室温储存时会迅速产生大量乳析，很少或几乎没有絮凝，没有聚结，并且液滴大小或浊度仅有微小变化。添加剂实际上减少了离心过程中的聚结程度。这种稳定性不同寻常。液滴大小和浊度主要取决于辛基酚聚氧乙烯醚9的浓度。当浓度从0.10%增加到约0.4%时，前者降幅最大，后者增幅最大。在25℃储存时，所有乳液都略微变粗。50℃时的稳定性受到硝酸铝和硝酸镁的损害，硫酸钠和氯化钠的损害程度较小。反向添加乳液比直接添加乳液对电解质的区分更明显。尤其是通过络合作用使辛基酚聚氧乙烯醚9盐析的电解质，通常能产生最细且最稳定的乳液。同样，使乳化剂盐析出来的电解质比使乳化剂盐析进去的电解质更能使二甲苯乳液不稳定。以7800 X g对十六烷乳液进行离心，将乳析的乳液层压缩成一个清澈、透明、各向同性的凝胶塞，在进一步离心时，聚结的十六烷会缓慢分离出来。（摘要截选至400字）
