Determination of extra virgin olive oil acidity by FIA-titration

A direct determination of extra virgin olive oil acidity by an automated fl ow injection titration is proposed. The oil sample (280 mul) is directly in jected, without dilution, in the carrier stream, a n-propanol solution flow ing at 2 ml/min and containing potassium hydroxide 1 mM as titrant and phen olphthalein 5 10(-5) M as indicator. In the mixing chamber(1.5 mi) the samp le mixes and reacts with the carrier stream. By an optical fiber beam, conn ected to a spectrophotometer set at 562 nm, we are able to appreciate conti nuously the phenolphthalein absorbance (Abs) decrease. The area of the peak "Delta Abs vs, time" has a linear correlation with the logarithm 1 of the sample acidity. Several extra virgin olive oil samples have been analysed. The correlation curve between the official (O) and proposed methods (P) is P = (0.02 +/-0.02) + (1.02 +/-0.03)O, with r(2) = 0.997 and s(r) = 0.033; t he accuracy and precision, expressed as mean error and RSD, are both <5%; t he number of samples analysed per hour, the solvent and the sample consumpt ion, in comparison with the official procedure, are respectively 12-60 vers us 7-8, 2-10 ml versus 100-150 ml and 0.5 ml versus 10-20 ml. These feature s and the simple procedure indicate how the proposed method could represent an interesting alternative to the European community official method for t he determination of free fatty acids in oil. <(c)> 2001 Elsevier Science Lt d. All rights reserved.