AN IMPROVED MICRO-EXTRACTION CELL FOR SUPERCRITICAL FLUID EXTRACTION AND CHROMATOGRAPHY OF FATTY-ACIDS

An improved supercritical fluid micro-extraction cell of increased reliability was designed for on-line supercritical fluid extraction and chromatography (SFE/SFC) of food and other lipid-related samples. The key components in the modified cell include a Swagelok stainless steel reducing union with a dual ferrule as the cell with polyetheretherketone (PEEK) ferrules and nuts to connect the cell to the control valve. The new cell did not leak under all conditions examined (100-500 atmospheres, 40-80-degrees-C), even after numerous extractions (> 250). The quantitative performance of the cell was evaluated with fatty acid standard solutions, technical grade fatty acid sources and wheat flour. The percent relative error (%RE) for the fatty acid standards and technical-grade fatty acid samples was less-than-or-equal-to 6.0% for oleic, linoleic and linolenic acid. The % RE for oleic and linoleic acid in the whole-wheat samples was less-than-or-equal-to 10%. The results demonstrate that the new extraction cell can be used for quantitative extractions and that the sensitivity of the SFE/SFC technique is excellent. Similar SFE/SFC methods could prove useful in studying the interaction of free fatty acids with various food components such as enzymes, amylose and proteins.