@article {2302, title = {Experimental determination of the third derivative of G. I. Enthalpic interaction}, journal = {Journal of Chemical Physics}, volume = {129}, number = {21}, year = {2008}, note = {ISI Document Delivery No.: 379XWTimes Cited: 2Cited Reference Count: 19Westh, Peter Inaba, Akira Koga, Yoshikata}, month = {Dec}, pages = {4}, type = {Article}, abstract = {The solute (i)-solute interaction in terms of enthalpy, H-i-i(E)=N(partial derivative H-2(E)/partial derivative n(i)(2))=(1-x(i))(partial derivative H-2(E)/partial derivative n(i)partial derivative x(i)), the third derivative of G, was experimentally determined using a Thermal Activity Monitor isothermal titration calorimeter for aqueous solutions of 2-butoxyethanol (BE) and 1-propanol (1P). This was done using both calorimetric reference and sample vessels actively. We simultaneously titrate small and exactly equal amounts of solute i (=BE or 1P) into both cells which contain the binary mixtures at an average mole fraction, x(i), which differs by a small amount Delta x(i). The appropriate amount of titrant delta n(i) was chosen so that the quotient (delta H-E/delta n(i)) can be approximated as (partial derivative H-E/partial derivative n(i)), and so that the scatter of the results is reasonable. delta H-E is the thermal response from an individual cell on titration, and we measure directly the difference in the thermal response between the two cells, Delta(delta H-E). The resulting quotient, Delta(delta H-E)/delta n(i)/Delta x(i), can be approximated as (partial derivative H-2(E)/partial derivative n(i)partial derivative x(i)) and hence provides a direct experimental avenue for the enthalpy interaction function. We varied the value of Delta x(i) to seek its appropriate size. Since H-E contains the first derivative of G with respect to T, the result is the third derivative quantity. Thus we present here a third derivative quantity directly determined experimentally for the first time.}, keywords = {AQUEOUS-SOLUTIONS, calorimetry, DYNAMICS, enthalpy, fluctuations, H2O, HOFMEISTER SERIES, LIQUID MIXTURES, MOLECULAR-ORGANIZATION, organic compounds, SOLVATION, WATER}, isbn = {0021-9606}, url = {://000261430900001}, author = {Westh, P. and Inaba, A. and Koga,Yoshikata} } @article {1237, title = {Effects of solvent flow, dopant flow, and lamp current on dopant-assisted atmospheric pressure photoionization (DA-APPI) for LC-MS. Ionization via proton transfer}, journal = {Journal of the American Society for Mass Spectrometry}, volume = {16}, number = {8}, year = {2005}, note = {ISI Document Delivery No.: 952BFTimes Cited: 42Cited Reference Count: 37}, month = {Aug}, pages = {1275-1290}, type = {Article}, abstract = {In this paper, the effects of solvent flow, dopant flow, and lamp power on proton transfer ionization in dopant-assisted (DA) atmospheric pressure photoionization (APPI) are investigated. A broad theoretical framework is presented, describing the primary photoionization process, the formation of protonated-solvent cluster ions, and the balance between analyte ion creation via proton transfer and loss via recombination. The principal experimental test system utilized methanol as the solvent, toluene as the dopant, and acridine as the analyte. Comparisons are made between acridine and a less basic compound, 9-methylanthracene (9-MA). Experimental determinations of the trends in the analyte MH+ signal and the total ion current (TIC) with variations in the subject parameters are provided. Experimental results and theory demonstrate that both the analyte signal and the TIC approach asymptotic limits with increases in dopant flow and/or lamp current (two factors which dictate the rate of photoion generation). The data show that these limits are lowered at higher solvent flow rates. These results are attributed to the recombination loss process, the rate of which increases with the second power of ion concentration. We deduce that the recombination rate constant increases with solvent flow rate, a consequence of the growth of ion-solvent clusters. Cluster growth is also believed to be a factor in the dramatic loss of sensitivity for 9-MA that occurs as the solvent flow is raised, because larger protonated-solvent cluster ions have greater solvation energies and may be unreactive with compounds having low gas-phase basicity and/or low solvation energy.}, keywords = {DETECTOR, GAS-PHASE, ION-SOURCE, LIQUID-CHROMATOGRAPHY, MASS-SPECTROMETRY, METHANOL, PLASMA, SENSITIVITY, SOLVATION, SYSTEM}, isbn = {1044-0305}, url = {://000230975700009}, author = {Robb, D. B. and Blades, M. W.} } @article {7145, title = {DIELECTRIC-RELAXATION OF LIQUID-MIXTURES}, journal = {Journal of Chemical Physics}, volume = {94}, number = {10}, year = {1991}, note = {ISI Document Delivery No.: FL001Times Cited: 15Cited Reference Count: 41}, month = {May}, pages = {6785-6794}, type = {Article}, abstract = {General expressions in terms of van Hove time correlation functions are given for the wave vector frequency-dependent dielectric function of multicomponent mixtures. The van Hove functions are obtained by applying the Kerr approximation and the dielectric relaxation at zero wave vector is considered in detail. At this level of theory, the frequency-dependent dielectric constant depends upon the self-reorientational correlation times of the various species involved and upon the equilibrium pair correlation functions. It is shown that if the self-correlation times are assumed to be given by the Stokes-Debye relationship, and if the equilibrium direct correlation functions obey certain relatively weak conditions, then for particles of equal size (i.e., the self-correlation times are the same for all species) the dielectric relaxation behavior can be described by a simple Debye formula with a single concentration-dependent relaxation time. This observation is independent of the number of components, of the concentration, and of the molecular dipole moments of the different species present. It may help explain why for some binary mixtures of polar molecules experimental measurements indicate only a single relaxation channel. The exact Kerr result for binary mixtures is expressed explicitly as the sum of two Lorentzians, and some numerical results are given for solutions of dipolar hard spheres of different diameter.}, keywords = {CONSTANT, DIPOLAR LIQUIDS, DYNAMICS, ELECTROLYTE-SOLUTIONS, INVARIANT EXPANSION, MEAN SPHERICAL MODEL, MOLECULAR LIQUIDS, ORNSTEIN-ZERNIKE EQUATION, SOLVATION, TRANSLATIONAL DIFFUSION}, isbn = {0021-9606}, url = {://A1991FL00100047}, author = {Wei, D. Q. and Patey, G. N.} }