Improved ozonolysis method for analysis of total n−3 fatty acids during hydrogenation of fish oils

A rapid and precise method for determining the total amount of n−3 fatty acids in small samples of fish oil is presented. The oil is ozonized at −10°C in hexane solution, and the ozonides are subsequently reduced with triphenyl-phosphine at 40°C. The propanal formed is quantitated by capillary gas chromatography. The method was utilized to follow the industrial hydrogenation of a fish oil, and it was demonstrated that the n−3 double bonds were simultaneously reduced to one-sixth as the iodine value decreased to one-half.