The determination of specific free fatty acids in peanut oil by gas chromatography

Peanut oil is dissolved in 2,2,4-trimethylpentane standard. The free acids are extracted into N,N-dimethylformamide as their sodium salts and treated with methyl iodide. The resulting methyl esters are analyzed by gas chromatography. A typical result for oleic acid is about 200 ppm with a relative standard deviation of 6%. An average recovery of 95% is obtained from a sample spiked with an additional 200 ppm of oleic acid. Evidence is presented that the procedure does not give high values as a result of sample hydrolysis.