Direct parallel flow injection multichannel spectrophotometric determination of olive oil iodine value Original Research Article

An automated parallel flow injection (PA-FI) spectrophotometric method for the determination of olive oil iodine value (IV, g I2/100 g of oil) is presented. A home made PA-FI analyzer, incorporating 10 incubation coils and using flow reversals, achieves a sampling rate of 60 samples per hour, while each sample is incubated for 10 min. Olive oil samples are diluted 1 : 50 in n-propanol and a 60 μl aliquot is injected into a 6.0 × 10−3 M IBr carrier solution prepared in acetic acid. The injected sample is mixed with the reagent while flowing through the detector and then diverted to the incubation coil, where it is incubated for 10 min. The sample is then aspirated for measurement by flow reversal. The IBr absorbance in the carrier stream is monitored continuously at 392 nm. Injected samples consume IBr, resulting in negative absorbance peaks. The linear range was 9–125 IV, that is suitable for the analysis of edible oils. The method was applied to the determination of IV of 25 olive oil samples. Results obtained by the proposed method compare well (0.1–1.7% relative difference, mean 0.7%) with those obtained by the official AOAC method, which is time consuming and uses large amounts of organic solvents. The relative standard deviation ranged from 0.4 to 1.1% (n = 6). The new PA-FI technique minimizes reagent and solvent consumption (3.1 ml of acetic acid per sample) and allows automation of methods that require long incubation times without loss of sampling rate. The method is environmental friendly since it eliminates the use of chlorinated solvents.