Extension of the chromatographic broadening method of measuring diffusion coefficients to liquid systems. I. Diffusion coefficients of some alkylbenzenes in chloroform

Abstract

The chromatographic broadening method of measuring diffusion coefficients, which until recently was used with gaseous mixtures, is shown to be useful for liquid mixtures. In this method, a small amount of solute (component 1) is injected into a flowing stream of a solvent (component 2). From the width of the eluted peak, the diffusion coefficient is measured. The constraints due to the liquid system, as well as possible sources of errors, are discussed. It is shown that with a well-designed injection port, a small-volume detector cell, narrow tubing, and low flow rate, good diffusion data can be easily obtained. Since the method is a dynamic one, the accumulation of the data is rapid, especially if a multiple-injection technique is used. The method was utilized to measure the diffusion coefficients of several alkylbenzenes in chloroform. It was found that as the side chain of the molecule lengthens, the diffusion decreases. The effect of molecular geometry was also investigated by observing the diffusion coefficients of structural isomers. The results seem to indicate that the more branched the molecule is, the faster the diffusion. The ramifications of these findings are discussed.

Peak dispersion and contributions to plate height in nonaqueous capillary electrophoresis at high electric field strengths: Propanol as background electrolyte solvent

“…The theoretical basis of the plate height model has been well established over the years, but one problem, especially in nonaqueous CE, is that some of the parameters needed in the calculations may be unavailable and additional measurements or approximations are required. To calculate the plate numbers theoretically, we measured the diffusion coefficients of the analytes by Taylor dispersion method [8][9][10] and as means of evaluating the extent of analyte adsorption to the capillary wall, we determined the distribution constants of the analytes chromatographically.…”

“…Diffusion coefficients of the analytes were measured by the Taylor dispersion method (also known as chromatographic peak broadening method) [8][9][10] on HP1050 LC equipment (Hewlett-Packard). With this method, analytes are simply carried through a very long capillary with pressure-driven flow.…”

“…The minus is used when the solvent (or migration) velocities are greater than 10 22 mm/s [10]. A stainless steel capillary with ID of about 0.79 mm and length of 103.3 m was used in the measurements.…”

Use of Taylor dispersion for the measurement of probe diffusion in polymer solutions

“…The technique was further developed by Pratt and Wakeham (1974) and Grushka and Kikta (1974). A number of restrictions and corrections to the analysis relating to sample injection, detector volume, tube uniformity, connecting volumes, and tube coiling can be applied, as reviewed by Alizadeh et al (1980).…”

Measurement of thermodynamic equilibria by chromatography

“…The same method has been applied in liquid chromatography [23,24] to determine diffusion coefficients at infinite dilution, mutual diffusion coefficients in liquids and self diffusion coefficients with a suitable marker.…”