Capillary gas chromatography of steroidal alkaloids from solanaceae : Retention indices and simultaneous flame ionization/nitrogen-specific detection

A capillary gas chromatography method for identification and quantification of Solanum and Lycopersicon C 27-steroidal alkaloids (SAs) was developed. Hydrogen was used as the carrier gas to achieve a relatively short analysis duration. Simultaneous flame ionization and nitrogen-specific detection (FID and NPD) enabled unambiguous differentiation between SAs and closely related non-nitrogen-containing compounds, such as sterols and steroidal sapogenins. Calibration plots for FID and NPD were linear for all individual SAs tested. The NPD/FID response ratios appeared to be an aid in identification and characterization of the compounds. Tuber samples of Solanum species varied in contents of solanidine glycosides from 600 to 6220 mg kg −1 fresh weight. Because of these larger differences, identification by retention times was not possible, but retention indices were sufficiently reproducible even for identification of the closely eluting Δ5- and 5α-aglycone pair solanidine and demissidine. Although, SAs are not usually easily quantified by capillary gas chromatography, quantitative analyses can be done routinely provided sufficient attention is paid to the accuracy and precision of the sample injection.