Gas chromatographic determination of indole and 3-methylindole (skatole) in bacterial culture media, intestinal contents and faeces.

A simple, rapid and inexpensive gas chromatographic method was developed for the determination of indole and 3-methylindole (skatole) in faeces, intestinal contents and bacterial cultures. It involves a simple homogenization and extraction with chloroform. The extract is injected onto a gas chromatograph equipped with a 12.5-m fused-silica capillary column coated with BP20 and a film thickness of 0.5 micron. To simplify the chromatograms and to get a higher sensitivity a nitrogen-phosphorus-sensitive detector is applied. The detection limit for indole and 3-methylindole under the conditions employed is 20 micrograms/kg, which is well below the values typically found in intestinal contents (up to 100 mg/kg). Recovery for both compounds was close to 100%, and the mean coefficients of variation were 3.5% for indole and 3.0% for 3-methylindole. The method has demonstrated its practical value in the analysis of more than 50,000 samples in our laboratory. More than 100 samples can be analyzed per day.