Simultaneous gas-chromatographic analysis of lower fatty acids, phenols and indoles in faeces and saliva using a fused silica glass capillary column

Abstract

The simultaneous gas-chromatographic separation of a mixture of 14 lower fatty acids, 11 phenols and 7 indoles was performed by using a fused silica glass capillary column of Carbowax 20M (50 m × 0.2 mm i.d., Carbowax 20M deactivated). Complete separation of the mixture was obtained, except for the peaks of phenols and o-cresol, o-ethylphenol and 3,5-xylenol and pelargonic acid, 2,3-xylenol and 1,2-dimethylindole, whose peaks overlapped, and 2- and 3-methylindoles, which were poorly separated. The optimum conditions are as follows: column temperature, held for 1 min at 100 °C; column oven, heated at 4 °C min^–1 from 100 to 220 °C, maintained at 220 °C for 9 min for standard compounds or 29 min for sample specimens, then cooled to 100 °C; and carrier gas (nitrogen) flow-rate, 0.97 ml min^–1. The method was applied to the analysis of the lower fatty acids, phenols and indoles in cat and human faeces and non-smoker saliva.