INFLUENCE OF TEMPERATURE, PRESSURE, MODIFIER, AND COLLECTION MODE ON SUPERCRITICAL CO2 EXTRACTION EFFICIENCIES OF DIURON FROM SUGAR-CANE AND ORANGE SAMPLES

The effects of temperature, pressure, modifier, and collection mode in the supercritical fluid extraction (SFE) of the herbicide Diuron (3-( 3,4-dichloro-phenyl)-1,1-dimethylurea) in real sugar cane and orange s amples were evaluated. The extraction efficiencies were directly compa red to those achieved using solid-liquid extraction (SLE) described in the literature with identical clean-up and analysis by high resolutio n gas chromatography-electron capture detection (HRGC/ECD). The SFE re coveries at temperatures lower than 80 degrees C and pressure lower th an 150 atm were typically lower than that obtained by SLE; however, an increase in the temperature and pressure increased the efficiencies o f SFE over SLE. The results showed that under certain conditions CO, i n the supercritical state presented higher extraction power than SLE ( extracted ca. 10% more pesticide), showing it to be a suitable method for pesticide residue analysis. (C) 1998 John Wiley & Sons, Inc.