CHAPTER 4
CONCLUSIONS
In this work, the downscaled methods have been developed for determination of iodine number of edible oils. The first approach was developed by modification of the conventional titrimetric method of AOAC. Iso-octane was used for dissolving oil samples. Using the small amount of sample was the key point for downscaling the method. Using 0.010 g samples required 1.00 mL of 0.10 M IBr solution and 1 min incubation time. This was at least 25 folds reducing the amounts of reagent and analysis time. The analytical results for determination of IN of oils obtained by the proposed method agree well with those by the AOAC method.
The second approach was proposed base on the spectrophotometric detection of tri-iodide species forming from the reaction of IBr with KI solution. Sample after treated with 1.00 mL of 0.10 M IBr solution was added with 1.00 mL of 15% w/v KI and the resulting solution was 200-folds diluted with water and adding 1.00 mL of 15% w/v KI solution prior to absorbance measurement. The absorbance measurement was made at 350 nm against the calibration blank. The calibration graph used for determination of excess IBr was constructed by plotting the absorbance versus IBr concentration. The graph was linear in the range of 0.04 to 0.10 M IBr with r2 of 0.9990. The amount of iodine absorbed could be calculated by subtraction of blank with sample determination and thus the iodine number was resulted. The results obtained by the proposed spectrophotometric method were good agreement with those by reference method.