The effect of geometrical deformation of open‐tubular extraction columns on peak dispersion of retained solutes is evaluated. By coiling or stitching of the columns peak dispersion is decreased, with a factor of two and more than five, respectively, due to secondary flow enhanced radial dispersion. This enables the increase of sampling flow rates in on‐line extraction‐GC using open‐tubular extraction columns up to 4 mL/min while still obtaining quantitative trapping of the analytes. © 1995 John Wiley & Sons, Inc. Copyright © 1995 John Wiley & Sons, Inc.