Simple & Easy Easy Way to Determine PUFA Content in Oils?

Quote: Originally posted by Bedlasky

Iodometric titration. Usually IBr is used instead of I2 due to better reactivity, but iodine still do the job. Add excess of I2 of known concentration (4 decimal places) to the flask with fat dissolved in chloroform, let it react for 30 minutes in stoppered flask in the dark, then titrate leftover I2 with thiosulfate of known concentration until purple coloration of CHCl3 disappears. If you will use IBr, add KI solution before titration with thiosulfate (IBr + I- --> I2 + Br-). Thiosulfate can be standardized with potassium dichromate, iodate or bromate, then it can be used for I2 standardization (or you can use pure ascorbic acid).

Quote: Originally posted by Bedlasky

Yes you can use ether. The point is that fat and iodine are well soluble in the solvent. When using Et2O, I would probably add some water and starch as a indicator before thiosulfate titration. I don't know how precise is end point without starch in Et2O, never tried it. Chlorinated solvents give nice end point with that disappearence of purple coloration. But yellow colour is less distinctive than purple so it may give you slightly lower volume at the end point. Starch offers very sharp end point because of its very distinctive blue colour.