DESIGN OF LIQUID-CHROMATOGRAPHY CAPILLARY COLUMNS

The theory of open tubular columns is extended to liquid chromatography without regard to the limitations of the associated chromatographic equipment. Methods are given to permit the optimum column length, radius and film thickness to be calculated to provide the minimum analysis time for any given separation. The basic data required are the separation ratio of the critical pair, the distribution coefficient between the stationary and mobile phase of the first eluted solute of the critical pair, its diffusion coefficient in the mobile phase, the separation ratio of the last eluted peak to the first eluted solute of the critical pair, the viscosity of the mobile phase and the maximum available inlet pressure. It is shown that, with the phase system considered, if the separation is to be achieved in the minimum time then the first solute of the critical pair should be eluted at a capacity factor (k′) of 2.7 irrespective of the separation ratio of the critical pair. Consequently the optimum film thickness depends solely on the optimum radius and the distribution coefficient of the solute between the two phases. Due to an optimum value for k′ being identified the equations for analysis time and column length are greatly simplified. © 1990.