Having followed this other chain, I am inclined to say that if you were less belligerent, but more precise you would long since have an answer. Though not having worked with FA for a few years, I will try to figure what you want: Apparently you should determine the unesterified fatty acids (UEFA) in the oil? If you have an oil, someone already did an extraction, possibly missing most of the UEFA, which are most likely at a very low concentration to start with (depending on what was extracted).
I am sure the literature has sundry examples, but one can imagine that TLC or HPLC could be used to separate all lipid classes, then one could do the BF3/MeOH on the UEFA fraction. Or, methylating only the UEFA with diazomethane might be a possibility. Also, extracting the UEFA into a basic aqueous solution (should be weakest possible?) might be a possibility.
