Buffering the aqueous phase pH in water-in-CO2 microemulsions
Buffering the aqueous phase pH in water-in-CO2 microemulsions
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DOI：
10.1021/jp990745v
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发表时间：
1999-07-08
影响因子：
3.3
通讯作者：
Johnston, KP
中科院分区：
文献类型：
--
作者：
Holmes, JD;Ziegler, KJ;Johnston, KP
在由全氟聚醚铵（PFPE-NH4）稳定的纳米级co2水微乳液滴中加入有机和无机缓冲剂，使pH值从3增加到5-7。采用亲水性指示剂4-硝基苯基-2-磺酸盐测定了温度、压力、缓冲液类型、缓冲液浓度、离子强度和CO2溶解度对水-CO2双相体系pH值的影响，并用热力学模型对pH值进行了准确预测。在这两个系统中，适度的缓冲负载导致pH值从2.5 pH单位急剧“跳跃”。pH值的进一步增加需要大量的碱来克服由于碳酸-碳酸氢盐平衡而产生的缓冲。在约1.5 mol kg(-1) NaOH的情况下，w/c微乳的pH值接近中性。在高缓冲液负载下，温度和压力对pH值的影响可以忽略不计。
The addition of organic and inorganic buffers to nanometer size water-in-CO2 microemulsion droplets stabilized by ammonium perfluoropolyether (PFPE-NH4) results in an increase in pH from 3 to values of 5-7. The effects of temperature, pressure, buffer type, buffer concentration, ionic strength, and CO2 solubility on the pH inside water-in-CO2 microemulsions and on biphasic water-CO2 systems were measured by the hydrophilic indicator 4-nitrophenyl-2-sulfonate and were predicted accurately with thermodynamic models. In both systems, modest buffer loadings result in a steep pH "jump" from 2.5 pH units. Further increases in pH require large amounts of base to overcome buffering due to the carbonic acid-bicarbonate equilibrium. A pH approaching neutrality was obtained in w/c microemulsions with approximately 1.5 mol kg(-1) NaOH. At high buffer loadings, the effects of temperature and pressure on pH values are negligible.