Yanxiong Ke

A novel click chitooligosaccharide for hydrophilic interaction liquid chromatography.

A novel chitooligosaccharide stationary phase for hydrophilic interaction liquid chromatography (HILIC) was developed via click chemistry and showed great HILIC characteristics on separation of polar compounds and enrichment of glycopeptides.

Fingerprint analysis of Ligusticum chuanxiong using hydrophilic interaction chromatography and reversed-phase liquid chromatography

Fingerprint analysis is considered one of the most powerful approaches to quality control in traditional Chinese medicines (TCMs). In this study, a binary chromatographic fingerprint analysis was developed using hydrophilic interaction chromatography (HILIC) and reversed-phase liquid chromatography (RPLC) to gain more chemical information about polar compounds and weakly polar compounds. This method was used to construct a chromatographic fingerprint of Ligusticum chuanxiong. The two chromatographic methods demonstrated good precision, reproducibility, and stability, with relative standard deviations of <2% for retention time and 7% for peak area for both HILIC and RPLC separations. Data from the analysis of 14 samples by HILIC and RPLC were processed with similarity analysis, with correlation coefficients and congruence coefficients. This binary fingerprint analysis, using two chromatographic modes, is a powerful tool for characterizing the quality of samples, and can be used for the comprehensive quality control of TCMs.

Facile synthesis of titania-zirconia monodisperse microspheres and application for phosphopeptides enrichment.

Monodisperse uniform zirconium-titanium mixed oxide microspheres (approximately 3 microm) with different zirconium/titanium ratios are easily synthesized (using Zr(acac)(4) and Ti(OBu)(4) as precursors) by a sol-gel method and have been characterized for their enrichment of phosphopeptides from standard protein alpha-casein.

Combination of off-line two-dimensional hydrophilic interaction liquid chromatography for polar fraction and two-dimensional hydrophilic interaction liquid chromatography × reversed-phase liquid chromatography for medium-polar fraction in a traditional Chinese medicine

Two-dimensional liquid chromatography (2-D LC) has been widely used for the analysis of complex samples owing to its great improvement in separation selectivity and peak capacity. However, one 2-D LC system may not be enough to meet the separation requirements due to the complexity of certain samples and respective limitations of two separation modes. In this work, water extract of Scutellaria barbata D. Don, a traditional Chinese medicine, was fractionated into polar fraction and medium-polar fraction by means of solid phase extraction (SPE). The fraction preparation made it easy to select the corresponding combination of 2-D LC method from hydrophilic interaction chromatography (HILIC) and reversed-phase liquid chromatography (RP-LC). An off-line 2-D HILIC×HILIC to analyze the polar fraction and an off-line 2-D HILIC×RP-LC to analyze the medium-polar fraction were developed, respectively. In total, 749 peaks were detected: 206 peaks from the polar fraction by the 2-D HILIC×HILIC and 543 from the medium-polar fraction by the 2-D HILIC×RP-LC. The practical peak capacities obtained in both systems were 2698 and 2879, and the orthogonality reached 63.18% and 90.62%, respectively. The results demonstrated that the two systems were both highly orthogonal, and the peak capacities greatly increased.

Click dipeptide : A novel stationary phase applied in two-dimensional liquid chromatography

2D-HPLC is an important technique for the separation of complex samples. Developing new types of stationary phases is of great interest to construct 2D-LC systems with high orthogonality. In this study, a novel stationary phase-Click dipeptide (l-phenylglycine dipeptide) was prepared by immobilization of alpha-azido l-phenylglycine dipeptide on alkyne-silica via click chemistry. In the preparation of this new material, an efficient, inexpensive and shelf-stable diazo transfer reagent (imidazole-1-sulfonyl azide hydrochloride) was utilized to transfer the amino group of l-phenylglycine to corresponding azido group under mild conditions. The Click dipeptide thus prepared was confirmed by FT-IR, solid state CP/MAS (13)C NMR and elemental analysis. The Click dipeptide packing showed high orthogonality with C18, which reached 63.5%. An off-line 2D-RP/RPLC system was developed to analyze a traditional Chinese medicine (TCM)-Rheum Palmatum L. The results showed high orthogonality between Click dipeptide and C18 as well as great separating power in the practical separation of complex samples.

Separation of carbohydrates using hydrophilic interaction liquid chromatography

A strategy was developed to rapidly evaluate chromatographic properties of hydrophilic interaction chromatography (HILIC) columns for separating carbohydrates. Seven HILIC columns (Silica, Diol, TSK Amide-80, XAmide, Click Maltose, Click β-CD, and Click TE-Cys columns) were evaluated by using three monosaccharide and seven disaccharides as probes. The influence of column temperature on the peak shape and tautomerization of carbohydrates, as well as column selectivity were investigated. The influence of surface charge property on the retention was also studied by using glucose, glucuronic acid, and glucosamine, which indicated that buffer salt concentration and pH value in mobile phase was necessary to control the ionic interactions between ionic carbohydrates and HILIC columns. According to evaluation results, the XAmide column was selected as an example to establish experimental schemes for separation of complex mixtures of oligosaccharide.

Selective separation of flavonoid glycosides in Dalbergia odorifera by matrix solid-phase dispersion using titania

Dalbergia odorifera contains high concentrations of flavonoid aglycones and trace flavonoid glycosides. In this study, trace flavonoid glycosides were separated from D. odorifera by titania with matrix solid-phase dispersion (MSPD). Before the MSPD experiment, four standards, including two isoflavone glycosides (genistin and formononetin-8-C-apiosyl (1-6)-glucoside) and their aglycones (genistein and formononetin), were used to compare their retention on a titania column. The effect of acetonitrile concentration and pH on their retention was investigated and a conclusion was drawn that high acetonitrile concentration and pH lead to the greatest difference in the retention of flavonoid as glycosides and aglycones. Besides hydrophilic interaction and ligand-exchange interaction may exist between sugar moiety of flavonoid glycoside and titania, so that flavonoid glycosides have stronger retention than that of aglycones. Based on the chromatographic rule of flavonoid as glycosides and aglycones on the titania column, the MSPD method was optimized to elute high concentration flavonoid aglycones first with 90% acetonitrile and 10% water containing 100 mM ammonium acetate buffer, and then to elute trace flavonoid glycosides with 20% acetonitrile and 80% water containing 1% trifluoroacetate (TFA). Isolated flavonoid glycosides were further analyzed by UPLC-MS/MS, and their fragmentation in MS(2) showed they are C-glycosyl flavonoids.

Analysis of cephalosporins by hydrophilic interaction chromatography

A simple hydrophilic interaction chromatography (HILIC) method was developed to analyze seven cephalosporins. These seven cephalosporins could be separated well on the Click β-CD column and Atlantis HILIC Silica column. The effects of buffer concentration and pH on the retention under HILIC mode were studied. Except cefepime hydrochloride (4), the retention of other six cephalosporins increased with increasing buffer concentration, while decreased with increasing pH. Different separation selectivities could be observed on the Click β-CD column and Atlantis HILIC Silica column, and changing pH also resulted in the changing of separation selectivity. The separations of cephalosporins by HILIC and reversed-phase high performance liquid chromatography (RP-HPLC) were compared, and the two separation modes had good orthogonality. In addition, cefotaxime sodium (1) and its degradation were separated well on the Click β-CD column, which indicated that the Click β-CD column by HILIC can be used for studying the stability of cephalosporins.

Large-pore monodispersed mesoporous silica spheres: synthesis and application in HPLC

Monodispersed mesoporous silica spheres (MMSS) with periodical large-pore size (up to 200 A) and uniform particle size (1-1.7 mum) have successfully been synthesized by utilizing a new kind of surfactant, and they also demonstrated great potential application in HPLC.

Pore expansion of highly monodisperse phenylene-bridged organosilica spheres for chromatographic application

Monodisperse phenylene-bridged organosilica spheres show great potential as chromatographic stationary phase. In this paper, the tunable particle size of monodisperse phenylene-bridged organosilica spheres were prepared by co-condensing different proportion of 1,4-bis(triethoxysilyl)benzene (1,4-BTEB) and tetraethylorthosilicate (TEOS), and then pore size was expanded by two-step post-synthesis hydrothermal treatments using N,N-dimethyldecylamine (DMDA)/dodecylamine (DDA) and tris-(hydroxymethyl)-aminomethane (TRIS) in turn. Phenylene-bridged organosilica spheres with particle size of 3.0-3.5microm and pore size of 85A were further surface modified by C(18) group and tested in reversed-phase high performance liquid chromatography (RP-HPLC). The primary chromatographic results demonstrated that C(18) bonded phenylene-bridged organosilica stationary phase has high retention and good chemical stability in the high pH mobile phase, which indicated that the phenylene-bridged organosilica can be used for HPLC packing supports.