The microstructural characteristics of water/AOT/isooctane microemulsions have been investigated by FT-IR spectroscopic technique. The broad peaks obtained for water OH and carbonyl bands have been resolved by Gaussian curve fitting, and the vibrational characteristics, particularly the peak intensity and peak area corresponding to each peak, have been analyzed. It has been observed that the aqueous core of the microemulsion droplet is composed of bound and free water while a small amount of water remains trapped in the interface. The maximum hydration number of AOT was found to be 12. The phenomena of rotational isomerism of the AOT molecule reported earlier with other techniques have also been revisited from the deconvoluted carbonyl bands of AOT molecule. IntroductionAerosol OT or AOT, i.e., sodium bis(2-ethylhexyl) sulfosuccinate, forms inverted micelles when dissolved in nonpolar solvents in which the sulfonate and ester head groups are pointed toward the polar side constituted by the aqueous core and the hydrocarbon chains are extended outside toward the continuous oil phase.'%2 These reverse micellar aggregates exhibit the remarkable ability to solubilize large amounts of water, resulting in the formation of water-in-oil microemulsions. The extent of water solubilization can be changed by adding organic or inorganic a d d i t i~e s .~.~ The micellization of AOT in nonpolar solvents and the influence of various additives on it were the subject of intense studies both from theoretical and experimental viewpoint^.^.^ The

We hypothesized that custom-designed microemulsions would effectively scavenge compounds from bulk media. Pluronic-based oil-in-water microemulsions were synthesized that efficiently reduced the free concentration of the local anesthetic bupivacaine in 0.9% NaCl. Both the molecular nature and concentration of the constituents in the microemulsions significantly affected extraction efficiencies. Pluronic F127-based microemulsions extracted bupivacaine more efficiently than microemulsions synthesized using other Pluronic surfactants (L44, L62, L64, F77, F87, F88, P104). Extraction was markedly increased by addition of fatty acid sodium salts due to greater oil/water interface area, increased columbic interaction between bupivacaine and fatty acids sodium salt, and greater surface activity. These data suggest that oil-in-water microemulsions may be an effective agent to treat cardiotoxicity caused by bupivacaine or other lipophilic drugs.

KJ/mole Figure 5. Framework stability as a function of Al-Al distance related to the location of Ni2+ ions in Ni-Aluminosilicate mordenite. Decreasing means increasing Ni2+ localization preference. The line is drawn as guide for the eye.vations. Firstly, the small differences in the relative lattice energies for Ni2+ located at the four different extra-framework sites indicate hardly any preferences on structural grounds. Secondly, the relative lattice energies of the Ni-alumina mordenites are observed to depend on the existence of specific Al-O-fSi-O^Al sequences in combination with a Ni2+ ion in close proximity (compare relative lattice energies in Tables III and IV). In particular, sequences with TV = 1 turned out to be very stable in comparison to sequences with TV > 1.Not only the value of TV but also the specific location of the Al-O-Si-O-Al sequences in the mordenite structure proves to be important. In this case (TV = 1), our calculations clearly show that Ni2+ is preferentially located in the 8-ring side pocket, followed by location in the 8-ring secondary pore system. Location of Ni2+ in the 12-ring main channel proves to be less favorable. These findings are illustrated in Figure 4.

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Oil-filled nanocapsules were synthesized using the oil droplets of an O/W microemulsion as templates. A polysiloxane/silicate shell was formed at the surface of the oil droplet by cross-linking n-octadecyltrimethoxysilane and tetramethoxysiloxane. The shell imparted stability to the oil droplets against coalescence. The nanocapsules can be used in a number of applications (i.e., biomedical or environmental) where the free concentration of lipophilic compounds must be reduced. As a proof, the nanocapsules (1.4% w/v oil content in saline) were shown to sequester quinoline (8 μM) from saline in <15 min. The removal process was followed in real time using the UV absorbance of free quinoline in solution. Our primary goal is to produce a system for drug detoxification therapy. As a proof of concept for sequestering drugs, the nanocapsules were used in the removal of free bupivacaine from normal saline solution. The free bupivacaine concentration was determined in the aqueous phase after contact with such nanocapsules using HPLC. The results showed a rapid removal of bupivacaine. The nanocapsules at a concentration of 0.1% w/v oil content showed a maximum removal capacity of ≈1900 μM bupivacaine.