title: Selective separation and purification of highly polar basic compounds using a silica-based strong cation exchange stationary phase.
abstract: Compared to moderately and weakly hydrophilic bases, highly polar basic compounds are even more difficult to separate due to their poor retention in reversed phase (RP) mode. This study described the successful applications of a strong cation exchange (SCX) stationary phase to achieve symmetric peak shape, adequate retention and selectivity in the separation of very polar basic compounds. Salt and acetonitrile concentrations were adjusted to optimize the separation. Good correlations (R(2)=0.998-1.000) between the logarithm of the retention factor and the logarithm of salt or acetonitrile concentration were obtained. Gradients generated by changing salt or acetonitrile concentration were compared for the analysis of different highly polar bases. Although all of the analytes were eluted more quickly with an acetonitrile gradient, the effect of the gradients tested on peak width and peak shape varied with respect to analyte. In addition, the effects of different types of cation and anion additives were also investigated. After separation parameters were acquired, the SCX-based method was utilized to analyze highly hydrophilic alkaloids from Scopolia tangutica Maxim with high separation efficiency (plate numbers>32,000 m(-1)). Concurrently, one very polar alkaloid fraction was purified with symmetric peak shape using the current method. Our results suggest that SCX stationary phase can be used as an alternative to RP stationary phase in the analysis and purification of highly hydrophilic basic compounds.
authors.affiliation: Key Lab of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Long
authors.forename: Zhimou
authors.initials: Z
authors.lastname: Guo
authors.forename: Xingya
authors.initials: X
authors.lastname: Xue
authors.forename: Xiuli
authors.initials: X
authors.lastname: Zhang
authors.forename: Lilly
authors.initials: L
authors.lastname: Nordahl
authors.forename: Xinmiao
authors.initials: X
authors.lastname: Liang
mesh_terms: D002411:Cation Exchange Resins; D002851:Chromatography, High Pressure Liquid; D012822:Silicon Dioxide / Q000737:chemistry*
chemical_list: D002411:Cation Exchange Resins; D012822:Silicon Dioxide
keywords: Highly hydrophilic bases; Natural product; Purification; Strong cation exchange; Symmetrical peak shape