Analysis of isoquinoline alkaloids using chitosan-assisted liquid-solid extraction followed by microemulsion liquid chromatography employing a sub-2-micron particle stationary phase

Modulation of retention and selectivity in oil-in-water microemulsion liquid chromatography: A review

Microemulsions (MEs) are stable, isotropically clear solutions consisting of an oil and water stabilized by a surfactant and a co-surfactant. Oil-in-water microemuslion liquid chromatography (MELC) is a relatively new chromatographic mode, which uses an O/W ME as mobile phase. Retention, selectivity and efficiency can be modified by changing the concentration of the ME components and the ratio between the aqueous and oil phases. This work makes a critical survey on the information found in the literature about the mobile phase compositions that lead to the creation of successful O/W ME mobile phases, as well as the effect of pH for ionizable compounds and temperature. The viability of performing the analyses using isocratic and gradient elution is also considered. The complexity of the composition of a successful ME, and the fact that the different factors interact each other, may require many manipulations during method development to achieve an acceptable separation for complex mixtures. This is the reason of the proposal from several authors of a standard ME as starting point when developing a method for a new separation with no previous reports. Based on these initial conditions, the interest of several authors in applying computer-assisted approaches to optimize the composition of ME mobile phases, and reduce significantly the time and reagent consumption for method development, is described. Some practical tips are given to prepare stable ME mobile phases that yield reproducible results.

Modification and Characterization of Fe₃O₄ Nanoparticles for Use in Adsorption of Alkaloids

Magnetite (Fe₃O₄) is a ferromagnetic iron oxide of both Fe(II) and Fe(III), prepared by FeCl₂ and FeCl₃. XRD was used for the confirmation of Fe₃O₄. Via the modification of Tetraethyl orthosilicate (TEOS), (3-Aminopropyl)trimethoxysilane (APTMS), and Alginate (AA), Fe₃O₄@SiO₂, Fe₃O₄@SiO₂-NH₂, and Fe₃O₄@SiO₂-NH₂-AA nanoparticles could be obtained, and IR and SEM were used for the characterizations. Alkaloid adsorption experiments exhibited that, as for Palmatine and Berberine, the most adsorption could be obtained at pH 8 when the adsorption time was 6 min. The adsorption percentage of Palmatine was 22.2%, and the adsorption percentage of Berberine was 23.6% at pH 8. Considering the effect of adsorption time on liquid phase system, the adsorption conditions of 8 min has been chosen when pH 7 was used. The adsorption percentage of Palmatine was 8.67%, and the adsorption percentage of Berberine was 7.25%. Considering the above conditions, pH 8 and the adsorption time of 8min could be chosen for further uses.

Construction of an optimized method for quality evaluation and species discrimination of Coptidis Rhizoma by ion-pair high performance liquid chromatography combined with response surface methodology

Coptidis Rhizoma (CR), the dried rhizome of three perennial Coptis specices, was widely used as a famous herbal medicine in China. Although the quantification of main alkaloids in CR has been extensively conducted, the existing analytical methods suffer from some flaws that restrict the general applicability in the routine quality assessment. In this work, we constructed an optimized method for quality evaluation and species discrimination of CR by ion-pairing high performance liquid chromatography (IP-HPLC) combined with response surface methodology (RSM). By employing Box-Behnken designs (BBD), 30 sets of experimental runs were performed to build the response surface models, and Derringer's desirability was used to optimize the IP-HPLC separation conditions by simultaneously taking resolutions between two pairs of hardly - separated alkaloids and the retention time of the last eluted analyte as optimization criteria. Meanwhile, a single standard to determine multi-components (SSDMC) method based on the optimized IP-HPLC was set up and fully validated, to simultaneously determine six alkaloids including jatrorrhizine (JAT), columbamine (COL), epiberberine (EPI), coptisine (COP), palmatine (PAL) and berberine (BER), using BER as internal standard. Finally, the quantitative data from 33 batches of CR samples were comparatively analyzed, and the ratios of JAT/COL and EPI/JAT were discovered for species classification. Collectively, the established IP-HPLC method can be adopted for comprehensive quality evaluation and species discrimination of CR due to its general applicability.