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Title: USE OF BIANARY GAS MIXTURES FOR SELECTIVE EXTRACTION OF PESTICIDES FROM FAT-LADEN SAMPLE MATRICES

Author
item Zhang, Zhouyao
item King, Jerry

Submitted to: ARS Food Safety and Inspection Service Research Workshop
Publication Type: Abstract Only
Publication Acceptance Date: 12/5/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Carbon dioxide (CO2) based supercritical fluid extraction (SFE) has become an increasingly important technique for extraction of trace chemicals from food samples. When SFE is used for residue chemical analysis of lipid rich samples, a time consuming clean-up step is often necessary to remove the lipid content from extracts before GC analysis. This lipid solubility in supercritical fluid can be significantly reduced when helium entrained CO2 is used as a gas source, although the reason for this phenomenon is not fully understood. In this study, an Anton Parr density meter and GC equipped with a thermal conductivity detector have been used to monitor the density and composition of the supercritical fluid generated from a helium headspace (HHS) CO2 cylinder over the duration of its use. The experiments show that the amount of helium dissolved in liquid CO2 decreases as the head pressure of the HHS CO2 cylinder drops. A binary CO2/nitrogen gas mixture as well as hexane/nitrogen mixtures have been used to extract pesticide residues in chicken fat. The presence of nitrogen significantly suppresses lipid solubility in fluids and allows selective extraction of trace pesticides from chicken fat. This new approach results in a clean extract from SFE of lipid rich samples and enables the direct GC analysis of the extract without resorting to a time consuming cleanup step.