Diffusion Coefficient Of Naphthalene Research Articles

Influence of solvent uptake and swelling by poly(styrene–divinylbenzene) column packings on sample sorption rate and band broadening in reversed-phase liquid chromatography

Porous poly(styrene–divinylbenzene) (PS–DVB) HPLC packings give broad, tailed peaks for some types of solutes. This phenomenon is due to sorption of these solutes into the polymer matrix where they experience very slow, hindered diffusion. It is known that the presence of small amounts of tetrahydrofuran (THF) in the methanol (MeOH)–H 2O mobile phase yields narrower and less tailed peaks for such solutes. In this study, Hamilton PRP-∞, a nonporous PS–DVB polymer, serves as a model for the matrix of porous polymers. The following measurements were made: sorption isotherms for MeOH and THF from aqueous solution; swelling of PRP-∞ as a function of activity of MeOH and THF in aqueous solution; and both sorption isotherms and sorption rate curves for the solute naphthalene from various solvent mixtures. The addition of 2% THF to 70:30 MeOH–H 2O produced an additional 0.4% swelling, an 11% decrease in the sorption capacity and a 90% increase in the diffusion coefficient of naphthalene in PRP-∞. The increase in the diffusion coefficient, which is responsible for the improved elution peak shape of naphthalene, is shown to be caused by the decrease in sorption capacity, rather than by the additional swelling. The sorbed THF serves to fill and “block” the smallest, most highly hindered micropores in the polymer matrix.

ChemInform Abstract: Transport and Relaxation of Naphthalene in Supercritical Fluids

The pressure dependence of diffusion coefficients of naphthalene in supercritical CO{sub 2} and naphthalene-d{sub 8} in supercritical ethylene has been measured by using the NMR fixed field gradient spin-echo Bessel function analysis technique. The pressure dependence of the reorientational motion of naphthalene-d{sub 8} in CO{sub 2} and ethylene has been studied by measuring the deuteron spin-lattice relaxation time, T{sub 1}, as a function of pressure at several isotherms. The temperatures were chosen to cover two regions of the naphthalene-supercritical solvent phase diagram. The experimental data allowed the molecular level test of the applicability of the Stokes-Einstein and Debye equations in the binary systems studied. The expression D({eta}/T){sup 0.75} = constant represents the experimental diffusion data well, and the modified Debye equation describes the reorientational motion of naphthalene in supercritical CO{sub 2} and ethylene solvents.

Diffusion coefficients of naphthalene and caffeine in supercritical carbon dioxide

An experimental set-up is presented with which the diffusion coefficients of naphthalene and caffeine in supercritical carbon dioxide may be determined. The experimental conditions range from 118 to 226 bar and from 35 to 60 °C. The method consists in evaporating the component to be analyzed out of capillaries into supercritical carbon dioxide. The diffusion coefficient can be calculated from the amount of evaporated material during an experimental run. The method is of the pseudo-steady-state type, whereas diffusion coefficients of naphthalene in carbon dioxide given in the literature were obtained with an unsteady-state method. Depending on experimental conditions, the unsteady method yields slightly lower values than the pseudo-steady method. It can be shown that the strongly non-ideal behavior of the gaseous phase restricts the range of application of the unsteady method.

Diffusion coefficient of naphthalene in air and hydrogen

Diffusion coefficient of naphthalene in air and hydrogen

Diffusion in viscous solvents. Part 4.—Viscosity and interdiffusion coefficients for solutions of carbon tetrabromide and of naphthalene in di-isobutyl phthalate and their dependence on temperature

Interdiffusion coefficients of carbon tetrabromide and of naphthalene dissolved in di-isobutyl phthalate have been obtained by following the isothermal relaxation of a concentration gradient induced by the application of a temperature gradient in the vertical direction in a thin horizontal film of the solution. Limiting diffusion coefficients at infinite dilution have been obtained over a range of temperatures and combined with some new data on the viscosity of the solvent to obtain ‘Stokes–Einstein numbers’. These are much lower than those expected on the basis of the Stokes–Einstein–Sutherland continuum model, being even lower than those found in diol solvents. However, the value found for naphthalene at 298 K in this ester solvent agrees closely with that derived from independent determinations of the diffusion coefficient of naphthalene in a hydrocarbon solvent having the same viscosity as di-isobutyl phthalate.

Diffusion coefficients of naphthalene and of α-iodonaphthalene in propane-1, 2-diol at 35°

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