Capillary supercritical fluid chromatography of pyrethrins and pyrethroids with positive pressure and negative temperature gradients

Abstract

Thermolabile molecules, such as pyrethrins and pyrethroids, are separated by supercritical fluid chromatography (SFC). Chromatography on a fused-silica capillary column is optimized by measuring the retention factor, peak resolution, and plate height. The separation of pyrethrins and pyrethroids by SFC was accomplished by the use of a positive pressure gradient and negative temperature gradient. The density of both gradients was comparable. Efficient separation of these pesticides was obtained with a linear isothermal pressure gradient of 0.2 MPa/min from 11.1 up to 22.3 MPa at a temperature of 90°C. Using a negative isobaric temperature gradient with a rate of −1.2°C/min from 130 down to 80°C, and holding 80°C for 10 min at 16.2 MPa, good results were obtained. The retention times of the analytes were constant.