sample preparation avoiding incomplete isolation of carboxylic acids consisted of deproteinization and extraction with ethanol , fixation of carboxylic acids as carboxylates , removal of interfering compounds such as neutral lipids by hexane extraction and amino acids , acyl carnitines and other cations by cation-exchange chromatography , derivatization of keto groups of ketocarboxylic acids into o-methyl oximes and benzyl ester formation by reaction of the potassium carboxylates with benzyl bromide via crown ether catalysis .
C0007066
carboxylic acids
C0022618
keto