Silver perchlorate in the mobile phase for rapid separation and determination of a pair of positional isomers in Inula racemosa Hook.f. with RP-HPLC

•Silver perchlorate as mobile phase additives to improve the separation of alantolactone and isoalantolactone on C18 column.•Silver perchlorate as mobile phase additives for the analysis of alantolactone and isoalantolactone was established.•The chromatographic separation of alantolactone and isoalantolactone was then carried out with good efficiency. Alantolactone and isoalantolactone isolated from many species of plants are a pair of positional isomers of CC bond. Previously, alantolactone and isoalantolactone have been proved to be good lead compounds for future anticancer agent development. Similarity of their molecular structures increases the separation difficulty for these two isomers on a conventional C18 column. Silver perchlorate (AgClO4) as mobile phase additives with RP-HPLC for improving the separation was developed for rapid determination of the positional isomers in Inula racemosa Hook.f. The effects of the concentration of silver perchlorate on the separation of the analytes were investigated. The composition of acetonitrile and water containing 5.0% silver perchlorate in a 65:35 (v/v) ratio was used as mobile phase, in which they were well separated within a short period of time on the C18 column. The method was successfully applied to determine them in an extract of Inula racemosa Hook.f. root. Silver perchlorate in mobile phase can efficiently improve the separation of the positional isomers and could be applied to rapidly determinate their content in this plant.