AN AUTOMATED FLOW-REVERSAL INJECTION LIQUID-LIQUID-EXTRACTION APPROACH TO THE DIRECT DETERMINATION OF TOTAL FREE FATTY-ACIDS IN OLIVE OILS

A continuous liquid-liquid extraction system based on an automated, si mplified single-channel now-reversal injection mode involving no segme ntation or separation unit is proposed for the direct determination of total free fatty acids (FFA) in olive oils. It relies on the reaction between the Cu2+-pyridine complex and FFA, which takes place at the o rganic-aqueous interface, the Cu2+-FFA complex (copper soap) thus form ed being extracted into the organic phase during the flow-reversal pro cess. Continuous monitoring of the organic phase at 716 nm by means of a photometer located in the middle of the injection loop provides a m ulti-peak absorbance-time profile representing multiple reversals in t he dynamic extraction process. Total FFA can thus determined in conten ts from 0.01 to 1.5% (3.5 X 10(-4)-5.3 X 10(-2) M) for oleic acid in t oluene-diluted oil samples (corresponding to 0.06-9.0% of FFA for orig inal samples) with relative standard deviations in the range 4.9-7.8% and a sampling frequency of 12 h(-1). The results provided by the prop osed method are in accordance with those obtained with a manual proced ure and comparable to those afforded by a standard acid-base titration method after appropriate correction.