OPTIMIZATION OF SEPARATIONS IN SUPERCRITICAL FLUID CHROMATOGRAPHY USING A MODIFIED SIMPLEX ALGORITHM AND SHORT CAPILLARY COLUMNS

A modified simplex algorithm has been used to optimize supercritical fluid chromatography (SFC) separations of samples containing nonhomologous, nonoligomeric components. Short capillary columns are employed in the initial separations, with a transfer to a longer column for greater efficiency as needed. Two chromatographic response functions, based on peak-valley ratio or threshold resolution criteria, were found to be suitable for SFC. Two- and three-variable Simplexes utilizing (i) density gradient rate and temperature, (ii) simultaneous pressure and temperature gradient rates, or (iii) initial density, density gradient rate, and temperature provided good results for the samples in this study. Convergence to the global optimum was shown for case I by restarting the simplex in another part of the parameter space. A synthetic mixture of three difficult-to-separate sesquiterpene lactones was separated by optimization on a short column using the three-parameter simplex and then transferring the method to a longer column. © 1990, American Chemical Society. All rights reserved.