Duncan P Brent, Needham David
Department of Mechanical Engineering and Materials Science, Duke University, Durham, North Carolina 27708-0300, USA.
Langmuir. 2006 Apr 25;22(9):4190-7. doi: 10.1021/la053314e.
The Epstein-Plesset model was originally derived for the dissolution of a single gas bubble in an infinite aqueous solution (Epstein, P. S.; Plesset, M. S. J. Chem. Phys. 1950, 18, 1505-1509). The micropipet manipulation technique was previously shown to test this theory on air microbubbles and air-filled lipid-coated microparticles accurately and appropriately (Duncan, P. B.; Needham, D. Langmuir 2004, 20, 2567-2578). This same theory is now tested to model liquid microdroplet dissolution in a well-defined solution environment. As presented previously for the gas-bubble system, holding a single microparticle at the end of a micropipet was not shown to affect the dissolution profile and allowed isotropic diffusion significantly, a necessary condition for the validation of the theory. Here, an aniline-water system with an initial droplet diameter of 50 microm was used as a model liquid-liquid system. A microdroplet of aniline in an aqueous solution presatureated with aniline at distinct levels was tested, as was the reverse system of a water droplet in an aniline solution. The dissolution lifetime was shown to increase with increasing medium saturation fraction according to the Epstein-Plesset time-dependent theory (including the time required to establish the stationary layer) neglecting interfacial tension. The droplet lifetime can be increased by an order of magnitude (from about 10 to 100 s) by increasing the saturation fraction from 0 to 0.9 and by another order of magnitude by increasing from 0.9 to 0.99. The technique proved to be an accurate and appropriate method to test the dissolution of single liquid microdroplets in a second liquid solution and establishes a systematic experimental and theoretical approach to the investigation of the formation of polymer and other microparticles.
爱泼斯坦-普莱塞特模型最初是为单个气泡在无限水溶液中的溶解而推导出来的（爱泼斯坦，P.S.；普莱塞特，M.S.《化学物理杂志》1950年，第18卷，1505 - 1509页）。先前已证明微量移液管操作技术能够准确且适当地在空气微泡和充空气的脂质包被微粒上验证该理论（邓肯，P.B.；尼达姆，D.《朗缪尔》2004年，第20卷，2567 - 2578页）。现在，运用同一理论对在明确界定的溶液环境中液体微滴的溶解进行建模。如先前针对气泡系统所阐述的那样，将单个微粒固定在微量移液管末端并未显示会影响溶解曲线，并且能显著实现各向同性扩散，这是该理论验证的必要条件。在此，以初始液滴直径为50微米的苯胺 - 水系统作为模型液 - 液系统。测试了在不同苯胺预饱和水平的水溶液中的苯胺微滴，以及在苯胺溶液中的水滴的反向系统。根据忽略界面张力的爱泼斯坦 - 普莱塞特时间相关理论（包括建立静止层所需的时间），溶解寿命显示随着介质饱和分数的增加而增加。通过将饱和分数从0增加到0.9，液滴寿命可增加一个数量级（从约10秒增加到100秒），从0.9增加到0.99时又可增加一个数量级。该技术被证明是测试单个液体微滴在第二种液体溶液中溶解的准确且合适的方法，并为聚合物和其他微粒形成的研究建立了系统的实验和理论方法。
