Conjugated linoleic acid determination in human milk by fast-gas chromatography

An efficient direct method for measuring c9,t11- and t10,c12-conjugated linoleic acid (CLA) isomer content in human and rat milk was developed and validated using an RTX-2330 capillary column (40 m × 0.18 mm × 0.1 μm). In comparison with the commonly used 100 m × 0.25 mm × 0.20 μm columns, this new type of fast column allowed the separation of FAMEs with the same resolution but in much less time. An additional advantage for biological samples was that only a small volume of sample was needed. Two different procedures were tested in order to select the best methylation of CLA isomers, and the alkali plus acid-catalyzed procedure was selected. The precision results showed relative standard deviations (R.S.D.) of repeatability and reproducibility ranging between 0.10 and 8.71%. The application of this method to human and rat milk samples showed that it was a rapid, simple and reliable method for the analysis of biological samples.