Supercritical fluid extraction of plant and environmental samples

Since the inception of analytical supercritical fluid extraction (SFE) in the early 80's, this technique has garnered great attractions in the extractions of variety of analytes from variety of matrices. In this study. supercritical carbon dioxide (SC CO2) has been examined as a sample preparation method for the extraction of eugenol from plant matrix prior to high performance liquid chromatography (HPLC) analysis and for the extraction of organochlorine pesticides (OCPs) from sewerage sludges and chlorpyrifos from formulation and soil samples prior to capillary gas chromatography (GC) analysis. This is an area of considerable interest as many current methods use environmentally hazardous chlorinated solvents and alternative methods are required. Although numerous studies have examined the potential application of SFE to isolate pesticides and plant products, the work has been qualitative rather than quantitative. The present work describes studies which have examined the supercritical conditions needed for complete extraction of the pesticides and plant product eugenol. Initially a complex matrix sludge was chosen. Later a simple matrix soil was chosen and a single pesticide chlorpyrifos was used as the SFE of sludge was unsuccessful. In the extraction of chlorpyrifos problems were encountered in the trapping of the extract on depressurisation of the SC CO2. The effect of collection solvent, CO2 flow rate, solvent depth, and restrictor heating on the trapping efficiency have been investigated. Two methods of trapping were evaluated. Once a quantitative trapping method was established, the effect of different soil matrices on the recovery of chlorpyrifos at different chlorpyrifos spiking level was investigated. The SFE of soil was compared to Soxhlet extraction.