Chiang Mai Journal of Science

A flow injection (FI) system with amperometric detection has been proposed for the determination of iodine value (IV) of vegetable oils. An aliquot of a sample of 0.010-g was treated with 1.00 mL of Hanus solution for 1 minute before adding with potassium iodide solution to generate tri-iodide. Then, the solution was injected into the FI-amperometric system to detect the tri-iodide by using a screen-printed carbon electrode (SPCE) at an applied potential of 750 mV (vs Ag/AgCl). The system was optimized to provide high sensitivity by utilizing various concentration of Hanus solutions for constructing a calibration graph, which was linear in a range of 40-100 μM (r² = 0.997) with limit of detection of 3.6 IV. An injection frequency of 60 h^-1 was achieved by using 2.5 mL/min flow rate. A good repeatability of injection (0.20-0.58 %RSD, n=11) and good reproducibility for replicated analysis of 5 aliquots of a sample (1.07-1.36 %RSD) were demonstrated. The proposed method was successfully applied to vegetable oil samples with low to high iodine value. The proposed method offers high sample throughput and low reagent consumption.