Applications of supercritical fluid extraction and chromatography in residue analysis

When a substance is above its critical temperature and pressure it is called a supercritical fluid. Supercritical fluids have the extraction power of solvents while possessing the diffusivity of gases. These properties hold exciting prospects for modern residue analysis methods for pesticides and other environmental pollutants. Three new and novel applications for supercritical fluid extraction are presented in this text. A rapid method for extracting petroleum hydrocarbons from soil is presented as well as analysis by gas chromatography-mass spectrometry and supercritical fluid chromatography. The method gives extraction recoveries greater than 90% with total analytical times of less than 1 hour. Two new methods for extraction and analysis of fourth generation insecticides are also presented. Avermectin, a natural product insecticide, is extracted from soil and animal tissue with recoveries over 80% and with no additional clean-up requirement. Azadirachtin, a biorational larvicide, was extracted from soil and insect specimens with recoveries of 70% and better. Determination of some of the properties of modifiers in supercritical carbon dioxide as they relate to the eluotropic series is also discussed. Overall, a modifiers ability to enhance or decrease supercritical chromatographic capacity factors is dependent on the presence of a primary solvent-solute relationship. The presence or absence of such a relationship is independent of modifier presence