This International Standard specifies a method for the determination of the composition of fatty acids which are esterified in the 2-position (ß or internal position) of the triglyceride molecules in animal and vegetable fats and oils. Because of the nature of pancreatic lipase action, the method is applicable only to fats and oils with a melting point below 45 °C. The method is not unreservedly applicable to all fats and oils, particularly those containing substantial amounts of — fatty acids with 12 or fewer carbon atoms (e.g. copra oil, palm kernel oil, butyric butter fats); — fatty acids with 20 and more carbon atoms and of a high degree of unsaturation (more than four double bonds) (e.g. fish oil and marine animal oil); — fatty acids which have secondary groups containing oxygen. NOTE — Fatty acids with double bonds in the (n-16) to (n-11) position (e.g. petroselinic acid) are converted only very slowly by pancreatic lipase. This may lead to wrong results.