Phenol blue

Such a behavior was first observed with 1,10-phenanthroline [235,236] and bromo-phenol blue [237], and the above relationships were confirmed by measuring the voltam-mograms of various drugs as a function of pH [238 240]. 

Fujisawa, T., Fukuda, M., Terazima, M., and Kimura, Y, Raman spectroscopy study on solvation of diphenylcyclopropenone and phenol blue in room temperature ionic liquids, /. Phys. Chem. A, 110, 6164-6172, 2006. 

A third example can be taken from analytical chemistry. Absorption and resonance Raman spectra of phenol blue were measured in liquid and supercritical solvents to determine the solvent dependence of absorption bandwidth and spectral shifts. Good correlation between absorption peak shift and resonance Raman bands and between Raman bands and bandwidth of C-N stretching mode were observed while anomalous solvent effect on the absorption bandwidth occnrred in liquid solvents. Large band-widths of absorption and resonance Raman spectra were seen in supercritical solvents as compared to liquid solvents. This was dne to the small refractive indices of the supercritical solvents. The large refractive index of the liqnid solvents only make the absorption peak shifts withont broadening the absorption spectra (Yamaguchi et al., 1997). 

When the solution is complete, add 50 ml of 0.05N hydrochloric acid, the first 10 ml drop by drop to precipitate the NC in a fine state of division, and then the remainder quickly until the whole quantity has been added. After 10 minutes add 2 ml of bromo-phenol blue solution and titrate with 0.1N sodium hydroxide. To confirm the endpoint, stop the stirrer, allow the NC to settle and compare the color of the supernatant liquid with that in a blank experiment, which must be carried out in an exactly similar manner, except that the propellant is omitted... 

Many color reagents are applicable to the oligosaccharides. Some of those used are ammoniacal silver nitrate,60 resorcinol-hydrochloric acid for inulin hydrolyzates,137 acidic benzidine for maltodextrins,138 Bromo-phenol Blue or p-anisidine-hydrochloric acid for galactosiduronic acids,130 and alkaline copper reagent with phosphomolybdic acid for dextrins.71... 

Solvatochromic shift data have been obtained for phenol blue in supercritical fluid carbon dioxide both with and without a co-solvent over a wide range in temperature and pressure. At 45°C, SF CO2 must be compressed to a pressure of over 2 kbar in order to obtain a transition energy, E, and likewise a polarizability per unit volume which is comparable to that of liquid n-hexane. The E,j, data can be used to predict that the solvent effect on rate constants of certain reactions is extremely pronounced in the near critical region where the magnitude of the activation volume approaches several liters/mole. 

Solvatochromic data, specifically absorption or transition energies (E s), have been obtained for the dye phenol blue in supercritical fluids as a function of both temperature and pressure. These data will be used to compare the "solvent strength" of these fluids with liquid solvents. He will use the terms "solvent strength" and "Et" synonymously in this paper such that they include the magnitude of the polarizability/volume as well as the dipole moment. The "solvent strength" has been characterized by the spectroscopic solvatochromic parameter, E, for numerous liquid solvents (9 JU, J7,JJ3). 

Phenol blue (benzoquinone N-[(4-dimethylamino) phenyl] imine, Aldrich >97%) was purified by recrystallization and chromatographic separation (30). The purity was checked by the melting point (161-162°C), and the absorption maximum in acetone (582 nm) and in CC14 (565 nm). The dye was of chromatographic purity as determined by thin-layer chromatography on silica gel. 

The cell was loaded with 10 5g phenol blue, evacuated, and pressurized with the solvent. A spectrum was obtained at a given pressure after the temperature and absorbance equilibrated. The absorption band was scanned over a range of 450-600 nm 2-3 times to obtain the average X. The reproducibility in X was 0.2 nm... 

Solvent strength in the critical region. All of the experiments were performed with the dye phenol blue which has been well-characterized both experimentally and theoretically in liquid solvents (20,21,22). Since the dipole moment of phenol blue increases 2.5 debye upon electronic excitation (8), it is a sensitive probe of the local solvent environment. For example the absorption maxima occur at 550 and 608 nm in n-hexane and methanol, respectively. The excited state is stabilized to a greater extent than the ground state as the "solvent strength" is increased, which is designated as a red shift. 

At this pressure, the polarizability/volume of SF CO2 is a little less than that of n-hexane, which suggests that there are other molecular interactions between CO2 and phenol blue in addition to dispersion and induction. The likely possibilities include electron donor-acceptor forces and dipole-quadrupole interactions. 

Solvent effect on rate constants. In this section, the rate constant will be predicted qualitatively in CO2 for the Diels-Alder cycloaddition of isoprene and maleic anhydride, a reaction which has been well-characterized in the liquid state (23,24). In a previous paper, we used E data for phenol blue in ethylene to predict the rate constant of the Menschutkin reaction of tripropylamine and methyliodide (19). The reaction mechanisms are quite different, yet the solvent effect on the rate constant of both reactions can be correlated with E of phenol blue in liquid solvents. The dipole moment increases in the Menschutkin reaction going from the reactant state to the transition state and in phenol blue during electronic excitation, so that the two phenomena are correlated. In the above Diels-Alder reaction, the reaction coordinate is isopolar with a negative activation volume (8,23),... 

The rate constant data for the Diels-Alder reaction of isoprene and maleic anhydride (23,24) may be correlated with IL of phenol blue at 35°C by... 

Local solvent compression. The next application of the solvato-chromic data will be to determine the magnitude of the local compression of a supercritical fluid solvent in the immediate environment of the solute. The of a dye such as phenol blue can be predicted in liquids where no specific interactions are present by treating the solvent as a homogeneous polarizable dielectric (22,29). The intrinsic "solvent strength", E, °, describes dispersion, Induction, and dipole-dipole forces and is given by (22). 

For phenol blue, the E, is zero for ethylene and CF3CI, but nonzero for the Lewis acids CF3H and CO2. One of the attractive features of solvatochromic scales is that the non-specific and specific interactions may be separated since the former can be calculated straightforwardly using Eq. 5. 

Figure 5. E of phenol blue in ethylene vs. density (0= 25 °C, A= 10 °C, and ---- is calculated E using Equation 5).

The final set of solvatochromic data are shown in Figure 6 for phenol blue in SF C02 doped with various amounts of the co-solvent or entrainer, methanol. Consider a pressure of 100 bar where the Et of phenol blue in C02 is 54 kcal/mol. The red shift is increased more by the addition of 3.5 mole percent methanol at constant pressure than by an increase in the pressure of pure C02 of over 200 bar. The large specific "solvent strength" of methanol causes this behavior. The red shift caused by the co-solvent is in... 

Ammonium Indol phenol blue colorimetry, ion chromatography... 

The unimolecular micellar characteristics of this poly(ammonium carboxylate) 156 were demonstrated 179 by UV analysis of guest molecules, such as pinacyanol chloride, phenol blue, and naphthalene combined with fluorescence lifetime decay experiments employing diphenylhexatriene as a molecular probe. The monodispersity, or absence of intermolecular aggregation, and molecular size were determined by electron microscopy. 

Hexapus in water solubilizes cholesterol, phenol blue (Kassoc = 1.0 x 104 M 1), naphthalene, and hydrophobic esters. Thus, hexapus seems non-selective in its binding characteristics (just like micelles). Universal binding has the advantage that almost any water-insoluble compound can be collected by the host molecule without regard to subtle structural variations. On the other hand, potential catalysts based on hexapus and other multi-armed systems would not be expected to manifest high specificity. Flexible chains do not lend themselves to a precise fit. 

Gently stir 100 ml formamide with 5 g Amberlite MB1 (mixed bed resin) for 30 min. Remove resin by filtration. Add 0.3 g xylene cyanol FF, 0.3 g bromo-phenol blue and Na2EDTA to 10 mM. Store at 4°C. 

EDTA, 0.1% (wt/vol) xylene-cyanol, 0.1% (wt/vol) bromo-phenol blue... 

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