CAPILLARY SUPERCRITICAL-FLUID CHROMATOGRAPHY OF PYRETHRINS AND PYRETHROIDS WITH POSITIVE PRESSURE AND NEGATIVE TEMPERATURE-GRADIENTS

Thermolabile molecules, such as pyrethrins and pyrethroids, are separa ted by supercritical fluid chromatography (SFC). Chromatography on a f used-silica capillary column is optimized by measuring the retention f actor, peak resolution, and plate height. The separation of pyrethrins and pyrethroids by SFC was accomplished by the use of a positive pres sure gradient and negative temperature gradient. The density of both g radients was comparable. Efficient separation of these pesticides was obtained with a linear isothermal pressure gradient of 0.2 MPa/min fro m 11.1 up to 22.3 MPa at a temperature of 90 degrees C. Using a negati ve isobaric temperature gradient with a rate of -1.2 degrees C/min fro m 130 down to 80 degrees C, and holding 80 degrees C for 10 min at 16. 2 MPa, good results were obtained. The retention times of the analytes were constant. (C) 1998 Elsevier Science B.V.