Author： Wan Peter Dowd Michael Thomas Audrey Butler Boyce
Publisher： Springer Publishing Company
ISSN： 0003-021X
Source： Journal of the American Oil Chemists' Society, Vol.84, Iss.8, 2007-08, pp. : 701-708
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Abstract
Thirty-one samples of vegetable oils were analyzed for free fatty acid (FFA) concentration by titration against sodium hydroxide and by trimethylsilyl (TMS) derivatization followed by gas chromatography (GC). In preliminary experiments, two silylation chemistries and three GC stationary phases were tested for TMS fatty acid ester formation and separation. No ideal combination of conditions was identified; however, hexamethyldisilazane with an acid catalyst and a non-polar J & W DB-5 column were chosen for comparison of the two approaches. Over the range of FFA values studied (0.04–12%), the results from the two methods were highly correlated (R > +0.996) and were generally in good agreement. However, values from the chromatographic method were slightly lower than values obtained by titration for the crude oil samples (which had higher FFA levels). For oils with >0.4% FFA, the GC approach was slightly less reproducible (average coefficient of variance of ~3%) compared with the titration approach (average coefficient of variance of ~1.4%). For oils with <0.4% ffa,="" the="" coefficients="" of="" variance="" were="" higher="" (8–9%)="" and="" comparable="" between="" the="" methods.="">
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