Silver ion chromatography for peak resolution enhancement: Application to the preparative separation of two sesquiterpenes using online heart-cutting LC-LC technique

Abstract

Silver ion chromatography, utilizing columns packed with silver ions bonded to silica gel, has proved to be an invaluable technique for the analysis of some positional isomers. In this work, silver ion chromatography by combination with online heart-cutting LC-LC technique for the preparative separation of two sesquiterpenes positional isomers from a natural product was investigated. On the basis of the evaluation that silver ion content impacts on the separation, the laboratory-made silver ion columns, utilizing silica gel impregnated with 15% silver nitrate as column packing materials, were used for peak resolution improvement of these two isomers and the preparative separation of them in heart-cutting LC-LC. The relationship among the maximal sample load, flow rate and peak resolution in the silver ion column were optimized, and the performance of the silver ion column was compared with conventional C column and silica gel column. Based on the developed chromatographic conditions, online heart-cutting LC-LC chromatographic separation system in combination with a silica gel column and a silver ion column that was applied to preparative separation of these two isomers from a traditional Chinese medicine, Inula racemosa Hook.f., was established. The results showed that the online heart-cutting LC-LC technique by combination of a silica gel column and a silver ion column for the preparative separation of these two positional isomers from this natural plant was superior to the preparative separation performed on a single-column system with C column or silica gel column.

Appraisal of the Antioxidant Activity, Polyphenolic Content, and Characterization of Selected Himalayan Herbs: Anti-Proliferative Potential in HepG2 Cells

“…These herbs were shortlisted, based on the basis of their ethnopharmacological activities. Previous investigations have been performed to analyze the phytochemical profile of these herbs through analytical methods, such as FT-IR, NMR spectroscopy, and HPLC-DAD [ 14 , 28 , 29 , 30 , 31 ].…”

Determination of levetiracetam in human plasma by online heart‐cutting liquid chromatography: Application to therapeutic drug monitoring

“…Importantly, the photodiode array detection allows the prediction of peak purity, a significant advantage compared to the ultraviolet-based methods [20,21]. Besides, the online heart-cutting LC systems are inexpensive compared to MS instruments [23][24][25][26][27][28][29]. The method was successfully applied to the analysis of real samples for therapeutic drug monitoring.…”

“…The samples were diluted with methanol and just filtered prior to the analysis. The online heart-cutting LC method is advantageous compared to other methods due to the superior resolution for the separation of complex samples with minimal sample losses [24][25][26][27][28]. In this study, we developed a new online heart-cutting LC method for determining levetiracetam in human plasma.…”