USE OF TAYLOR-ARIS DISPERSION FOR MEASUREMENT OF A SOLUTE DIFFUSION-COEFFICIENT IN THIN CAPILLARIES

A method for the fast measurement oi the diffusion coefficients oi bot h small and large molecules in thin capillaries is reported. The metho d relies on Taylor-Aris dispersion theory and uses standard instrument ation for capillary zone electrophoresis. With this equipment, which c onsists of thin capillaries (50 to 100 micrometers in inner diameter), an injection system, detector ports, and computer data acquisition, a sample plug is pumped through the capillary at known velocity and the peak dispersion coefficient (D) is measured. With the experimentally measured values of D and flow velocity, and knowledge oi the inner d iameter df the capillary, the molecular diffusion coefficient (D) can be rapidly derived. For example, for ovalbumin a D value of 0.759 x 10 (-6) square centimeter per second is found versus a tabulated value of 0.776 x 10(-6) square centimeter per second (error, 2 percent). For h emoglobin a D value of 0.676 x 10(-6) square centimeter per second is obtained versus a literature value of 0.690 x 10(-6) square centimeter per second (error, 1.5 percent).