Improved GC/MS method for quantitation of n-alkanes in plant and fecal material.

A gas chromatography−mass spectrometry (GC/MS) method for the quantitation of n-alkanes (carbon backbones ranging from 21 to 36 carbon atoms) in forage and fecal samples has been developed. Automated solid−liquid extraction using elevated temperature and pressure minimized extraction time to 30 min per sample as compared to more than 24 h for traditional GC−flame ionization detection methods that use saponification and liquid−liquid extraction. Extraction solvent requirements were also minimized to 10 mL per sample. Under optimal conditions, complete method recoveries, including extraction efficiency, were greater than 91%. The linear dynamic range was 5 to 100 nmol injected onto the column, with a limit of quantitation of 5 nmol. Intra-assay coefficients of variation for the analysis of annual ryegrass (Lolium rigidum), subterranean clover (Trifolium subterranean), and bovine feces ranged from 0.1%−12.9%, where lower concentrations of n-alkane produced a higher degree of imprecision. The reported GC/MS m...