It will depend on your raw material: whether it is mostly acylglycerides or it contains a significant amount of free fatty acids. On the link above you will find the explanation for several methods
The book "Lipid Analysis: a practical approach" edited by R. J. and S. Hamilton is also very good with a whole chapter on derivatising fatty acids with methods. It's quite old (1992) but has some really good basic information in.
The easiest method is BF3- MeOH derivatization. BF3- MeOH reagent is available from Sigma-Aldrich-Supelco. If the sample is Fatty Acid, then you can directly add the reagent and derivatize. If the sample is a triglyceride, then you have to carry out saponification prior to the addition of the reagent. In case you need more information, please contact me on my mail i.d. : [email protected].
Thank you so much everyone for your valuable suggestions and solutions. I am going to use BF3/methnol to derivatize my fatty acids, extracted from Blood plasma