Agilent Technologies announces improved methods for analyzing fatty acids in foods
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PALO ALTO, Calif., April 22, 2002 Agilent Technologies Inc. today announced two improved methods for identifying fatty acids in foods.
Fatty acids can be isolated from most foods, especially from edible fats and oils derived from agricultural products such as corn, maize, olives and soybeans. Fatty acid analysis is preceded by saponification of the glycerols and derivitization to the fatty acid methyl esters (FAMEs). FAMEs are normally analyzed by gas chromatography (GC) or GC/mass spectrometry (GC/MS) on columns coated with polar stationary phases.
Chemists from Agilent Technologies, the Research Institute for Chromatography in Kortrijk, Belgium, and the University of Gent in Gent, Belgium, have developed two retention time locking (RTL) methods for analyzing FAMEs. RTL offers easy peak identification and simple comparison of data from different GCs and different laboratories. The choice between the two methods depends on sample complexity and the degree of fatty acid characterization required.
The first method uses a DB-WAX column that separates FAMEs according to carbon number (from C4 to C24) and fatty acid saturation. This method uses a gas chromatograph with flame ionization detector or mass spectrometer (GC/MS). The DB-WAX column does not separate cis and trans isomers, and for complex mixtures such as fish oils, does not resolve some FAMEs. However, this column is sufficient for most classical oil and fat characterizations. In addition, it can be used to characterize some animal fats such as butyric acid in milk fat, which is important in milk and dairy analysis and in the analysis of chocolate products.
The second method uses the same instruments as the first method but with a DB-23 cyanopropyl column. This method is appropriate for analyzing more complex samples such as fish oils, hydrogenated fats and cis and trans isomers.
Both methods use RTL , which allows analysts to obtain virtually identical retention times on any gas chromatograph, independent of inlet, injection technique or detector. This makes peak identification more accurate and allows easy correlation of results between instruments.
Agilent's published retention time database, which is available at no charge from www.agilent.com/ chem, enables rapid and reliable FAME identification. An additional benefit of RTL is that retention times in the calibration table remain unchanged, even after column maintenance or change. For GC/ MS, an available spectral library can screen data files using spectra in combination with their locked retention times.