COMPARISON OF TEMPERATURE AND ULTRASONIC INTENSIFICATION OF SUPERCRITICAL FLUID EXTRACTION USING PARSNIP SEEDS AS AN EXAMPLE

A comparison of thermal and ultrasonic intensification of supercritical fluid extraction using wild parsnip seeds, a source of plant oil and furocoumarin photosensibilizers, was conducted. It was observed that, even at pressure as high as 300 bar temperature effect on parsnip extraction demonstrates a so-called retrograde behaviour, that is, isobaric temperature increase leads decrease in extraction speed and overall mass yield. A previously proposed idea on a chromatography-like mechanism of a supercritical fluid extraction process with multiple re-adsorption of the isolated components onto the plant material working as a softent allows explaining the observance of retrograde behaviour, uncommon for such high pressure values. The overall influence of ultrasonic intensification of extraction process was shown to be similar to that of temperature. At low extraction pressure (100 bar), when cavitation of a subcritical fluid entering the extraction zone is principally possible, ultrasonication leads to an increased extraction kinetic at the initial, linear part of the extraction curve. At high working pressure (300 bar), effect of ultrasonication is essentially equal to that of direct heating. Using supercritical fluid chromatography, Furocoumarin profiles of thermal and ultrasonic parsnip extracts were shown to be identical by means of supercritical fluid chromatography, thus, ultrasonication even at 100 bar does not cause any unwanted sonochemical effects.