Li Laisheng

Enantioseparation and Determination of Propranolol in Human Plasma on a New Derivatized β-Cyclodextrin-Bonded Phase by HPLC

A 6-azido-β-cyclodextrin was synthesized and derivatized with p-nitrophenyl isocyanate as chiral ligand. Then the ligand was chemically bonded to mesoporous SBA-15 via a ‘Click Chemistry’ reaction of the azido group with alkynyl group. A new p-nitrophenylcarbamoylated β-cyclodextrin bonded SBA-15 chiral stationary phase (NPCSP) for HPLC was thus obtained. The new stationary phase was first used for enantioseparation of propranolol in human plasma under the polar organic solvent mode. The effects of methanol content, concentration of glacial acetic acid/triethylamine in mobile phase and the temperature on the enantioseparation were studied in detail. The optimized chromatographic conditions were as follows: mobile phase was acetonitrile/methanol/glacial acetic acid/triethylamine (90/10/1.25/2.25, V/V) at 288 K, with a flow rate of 0.5 mL min−1, an injection volume of 20 μL and detection wavelength at 290 nm. The resolution was 2.04 with a short run time (< 15 min) under the optimal conditions. The content of propranolol in plasma was quantitatively measured by HPLC-MS under selected ion monitoring mode ([M + H]+ m/z 260.10) with hydrochlorothiazide as an internal standard. The good linear relationship was observed in the range of 2.5−50 μg L−1. The detection limits were 1 μg L−1 according to S/N = 3 for both enantiomers. The experimental results showed that the chiral stationary phase exhibited excellent chiral separation ability to propranolol. The analytical method for propranolol enantiomers was sensitive, accurate, simple and fast, which was can be for the determination of propranolol in plasma and related pharmacokinetic studies.

Preparation and Characterization of a Baicalin-bonded Stationary Phase for High Performance Liquid Chromatograph

Abstract The solid–liquid reaction method was used for the preparation of a new High Performance Liquid Chromatography (HPLC) baicalin-bonded stationary phase (BBSP) via amido linkage, by using γ-aminopropyl trimethoxy silane (TM-550) as a coupling reagent and baicalin as a ligand. The structure of the ligand was characterized by Fourier transform infrared spectrum, elemental analysis, thermal analysis and so on. The chromatographic performances of BBSP were preliminarily evaluated, and a related retention mechanism was discussed by using different solutes as probes. Meanwhile, a comparative study between BBSP and conventional octadecyl-bonded stationary phase (ODS) was also carried out under the same conditions. The results showed that the new stationary phase had a relatively weak reversed-phase chromatographic property. Besides hydrophobicity, BBSP could also provide various sites, such as, hydrogen-bonding, π-π, and n-π charge transfer interactions. Synergistic interactions improved the separation selectivity of BBSP for aromatic compounds and their positional isomers when compared with ODS. It could also be observed that the polar amido linkage and hydrophilic glucose residue could minimize the residual silanols effect and improve the separation of basic nitrogen-containing compounds. Additionally, the new packing had strong affinity to flavonoids because of their similar structures. BBSP could be used as an enriching column packing for natural organic flavonoids from medicine herbs.

Preparation and Characterization of a Novel Isatin Derivative of beta-Cyclodextrin-bonded SBA-15 Stationary Phase for HPLC

An isatin derivative of β-cyclodextrin Schiff base was first synthesized by the condensation reaction between the carbonyl group of isatin and ethylenediamino group of the mono-substituted β-cyclodextrin. The Schiff base ligand was chemically linked to homemade ordered mesoporous SBA-15 silica gel via 3-( triethoxysilyl) propyl isocyanate coupling agent. In this way, a novel isatin derivative of β-cyclodextrin-bonded SBA-15 stationary phase( ISCDP) was prepared for HPLC. Its chemical and physical parameters were characterized by infrared spectroscopy, mass spectroscopy, elemental analysis, thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy, X-ray diffraction and BET specific surface area analysis. The basic chromatographic property of ISCDP was evaluated by using polar halogenated uracils and disubstituted benzene positional isomers as solute probes in reversed-phase chromatography. ISCDP was also used to enantioseparate two β-blocker drugs in polar organic mode and two dansyl amino acids in reversed-phase mode, respectively. The related chromatographic separation mechanism was also discussed. Above studies were expected to provide experimental basis for the practical application of ISCDP in the future. The results showed that the introduction of isatin indole ring could enhanced the reversed-phase chromatographic separation ability of ISCDP for halogenated uracils within 7 min. The new packing also exhibited high stereoselectivity for the position isomers of nitroaniline, aminophenol and benzenediol, in which the para isomers were finally eluted due to strong inclusion interaction between the isatin derivative of β-cyclodextrin ligand and the isomers. Meanwhile, the introduction of isatin indole ring could also improve the chiral separation ability of ISCDP. For example the fast enantioseparations of chiral β-adrenergic blockers and dansyl-amino acids on ISCDP were achieved within 20 min( Rs 1.3). Obviously, besides hydrophobicity, various synergistic interactions could enhance the separation selectivities of the new stationary phase for chiral and achiral analytes, including dipole-dipole, hydrogen bonding, π-π and inclusion interactions. The ordered pore structure of SBA-15 facilitated to fast and efficient separation and analysis for drugs with good permeability and low mass transfer resistance.