Simultaneous enhancement of fluorescence and thermal lensing by reversed micelles

Abstract

systems (5)) took longer in our system. However, in any event, the time required to achieve steady state after turning on the stirrer is not releuant to the discussion. This is because all reported absorbances were measured after the achievement of steady state. The relevant question is as follows: To what extent does the absorbance measured for the solution a t steady state (equilibrium) contain a contribution from solute that was released from the interface into the bulk solution during coalescence in the vicinity of the porous membrane? This is determined by the rates of desorption and diffusion, by the thickness of the Nernst film, and by the residence time of a "patch" of interface above the membrane, as we discuss in our paper, and is essentially independent of pumping rate and of volume" of pump tubing, connecting tubing, and detector cell.We find nothing in the criticism of Freiser (1) to alter in any way the model that we have proposed to explain the behavior of solute adsorbed a t the liquid-liquid interface in systems involving porous membrane phase separators. LITERATURE CITED(1) Freiser, H. Anal. Chem. 1987, 59, 000.(2) Persaud, G.; Tian, X-M.; Cantwell, F. F. Anal. Chem. 1987, 59, 2-7. (3) Chamupathi, V. G.; Freiser, H. Lsngmuir, In press. (4) Watarai, H.; Cunningham, L.; Freiser, H.

Studies of surfactant/water systems near the critical micellar concentration using thermal lens spectroscopy

“…All the concentrations considered here are significantly lower (at least two order of magnitude) than those employed by other authors [6,10,11]. We observe both enhancement and reduction of the experimental signal, depending on the surfactant and the effect is clearly related to micelle formation.…”

“…Specially relevant to the present work are the investigations of Mermet and Georges, and those of Franko and Tran [9][10][11][12][13]. Both groups found by different methodologies, that working with micellar solutions produces an enhancement in the thermal lens signal, for surfactant concentrations well above CMC.…”

“…[5][6][7][8] The CMC value is of practical importance as it defines the minimal concentration of surfactant, which is required to solubilize a hydrophobic molecule. The peculiar properties exhibited by micellar solutions may sometimes be very useful in analytical research [7,9,10,11]. The most important of these properties is the ability of micelles to solubilize, within their microstructure regions, compounds which are insoluble or sparingly soluble in water.…”

The Use of Triton X-100 in Thermal Lensing of Aqueous Solutions

“…[1][2][3][4] Until now, a number of studies have dealt with surfactants as media modifiers in thermal lensing, but mainly in physicochemical studies. [5][6][7][8][9][10] The aims of this work were (1) to study the effect of an inert nonionic surfactant (Triton X-100) on performance characteristics of thermal lensing of iron(II)-1,10-phenanthroline and cobalt(III)-2-nitroso-1-naphthol as model systems and (2) to use the change in the thermooptical properties of water for the determination of the surfactant itself. …”

Ionic Liquids for and by Analytical Spectroscopy

“…Conversely, water, which is the most powerful and widely used solvent in spectrochemical analysis is considered to be the worst medium for thermooptical techniques because it has very low dn/dT and high k values (Bialkowski 1996;Franko and Tran 1996). In fact, it was theoretically predicted and experimentally verified that for the same sample concentration and excitation laser power, the sensitivity of thermal lens measurements in volatile solvent such as carbon tetrachloride and benzene are about 40 and 26 times higher than that in water, respectively (Tran 1988;Tran and Van Flett 1988;Tran 1989, 1991;Baptista and Tran 1995). This is very unfortunate because it severely limits the scope of these techniques.…”