RUMINAL ORGANIC-ACID ANALYSIS BY GAS-CHROMATOGRAPHY MASS-SPECTROMETRY

Rumen fluid was analyzed by the gas chromatography/mass spectrometry (GC/MS) technique in order to identify the organic acids contained. The gas chromatogram obtained showed more than 200 peaks, and 60 organic acids were identified from their mass spectra obtained under electron impact conditions from the relative chromatographic peaks. Keto acids, polycarboxylic acids, hydroxy acids, aromatic acids, and saturated and unsaturated fatty acids were present, which were subdivided into three main groups: (i) short- and long-chain fatty acids; (ii) polyfunctional organic acids such as intermediate metabolic products; (iii) phenolic acids mainly from lignin and tannin degradation. It was concluded that GC/MS is a very specific and sensitive technique to detect the presence of fermentation products in biological fluids and that it could allow for the simpler and cheaper GC technique to be used for routine quantitative analyses of the identified compounds.