Solvent-modified MEKC for the enantioseparation of palonosetron hydrochloride and related enantiomeric impurities

Comparison of the Performance of Different Bile Salts in Enantioselective Separation of Palonosetron Stereoisomers by Micellar Electrokinetic Chromatography

Bile salts are a category of natural chiral surfactants which have ever been used as the surfactant and chiral selector for the separation of many chiral compounds by micellar electrokinetic chromatography (MEKC). In our previous works, the application of sodium cholate (SC) in the separation of four stereoisomers of palonosetron (PALO) by MEKC has been studied systematically. In this work, the parameters of other bile salts, including sodium taurocholate (STC), sodium deoxycholate (SDC), and sodium taurodeoxycholate (STDC) in the separation of PALO stereoisomers by MEKC were measured and compared with SC. It was found that all of four bile salts provide chiral recognition for both pairs of enantiomers, as well as achiral selectivity for diastereomers of different degrees. The structure of steroidal ring of bile salts has a greater impact on the separation than the structure of the side chain. The varying separation results by different bile salts were elucidated based on the measured parameters. A model to describe the contributions of the mobility difference of solutes in the aqueous phase and the selectivity of micelles to the chiral and achiral separation of stereoisomers was introduced. Additionally, a new approach to measure the mobility of micelles without enough solubility for hydrophobic markers was proposed, which is necessary for the calculation of separation parameters in MEKC. Under the guidance of derived equations, the separation by SDC and STDC was significantly improved by using lower surfactant concentrations. The complete separation of four stereoisomers was achieved in less than 3.5 min by using 4.0 mM of SDC. In addition, 30.0 mM of STC also provided the complete resolution of four stereoisomers due to the balance of different separation mechanisms. Its applicability for the analysis of a small amount of enantiomeric impurities in the presence of a high concentration of the effective ingredient was validated by a real sample.

Simultaneous separation and determination of four active ingredients in Picria fel-terrae Lour. and its preparations by micellar electrokinetic chromatography

INTRODUCTION

Picfeltarraenins IA, IB and IV and acteoside are the four bioactive ingredients of Picria fel-terrae Lour. Their pharmacological effects include central inhibitory, cardiovascular, anti-inflammatory, anti-pyretic, analgesic, anti-bacterial, antioxidative and anti-tumor effects.

OBJECTIVE

We aimed to develop an efficient micellar electrokinetic chromatography (MEKC) method modified with mixed organic solvents for the simultaneous separation and determination of the four components in Picriae Herba and its formulations.

METHODS

Method optimization was carried out by investigating influences of significant factors on the separation, and this method was successfully applied for the determination of the four components in Picriae Herba and its formulations.

RESULTS

The optimal running buffer was composed of 20 mM sodium tetraborate, 40 mM sodium cholate, 10% (v/v) methanol and 10% (v/v) isopropanol (pH 9.76). The separation voltage was 18 kV, the temperature was 25°C and the detection wavelength was 266 nm. Under the optimal separation conditions, the baseline separation of four components was achieved in less than 14 min. The correlation coefficients of the calibration curves were 0.9984-0.9995 for the analytes. The intraday and interday precision ranged from 1.5% to 2.5% and from 1.4% to 5.0%, respectively. Recoveries of analytes varied from 96.6% to 104.1%.

CONCLUSION

The method was proved suitable for the determination of four components in Picriae Herba and its formulations. Good performance was obtained under optimal conditions, and the method provides an effective tool for the quality control of Picriae Herba and its formulations.

Bile Salts in Chiral Micellar Electrokinetic Chromatography: 2000-2020

Bile salts are naturally occurring chiral surfactants that are able to solubilize hydrophobic compounds. Because of this ability, bile salts were exploited as chiral selectors added to the background solution (BGS) in the chiral micellar electrokinetic chromatography (MEKC) of various small molecules. In this review, we aimed to examine the developments in research on chiral MEKC using bile salts as chiral selectors over the past 20 years. The review begins with a discussion of the aggregation of bile salts in chiral recognition and separation, followed by the use of single bile salts and bile salts with other chiral selectors (i.e., cyclodextrins, proteins and single-stranded DNA aptamers). Advanced techniques such as partial-filling MEKC, stacking and single-drop microextraction were considered. Potential applications to real samples, including enantiomeric impurity analysis, were also discussed.

Capillary electrophoresis methods for impurity profiling of drugs: A review of the past decade

Capillary electrophoresis (CE) is widely used for the impurity profiling of drugs that contain stereochemical centers in their structures, analysis of biomolecules, and characterization of biopharmaceuticals. Currently, CE is the method of choice for the analysis of foodstuffs and the determination of adulterants. This article discusses the general theory and instrumentation of CE as well as the classification of various CE techniques. It also presents an overview of research on the applications of different CE techniques in the impurity profiling of drugs in the past decade. The review briefly presents a comparison between CE and liquid chromatography methods and highlights the strengths of CE using drug compounds as examples. This review will help scientists, fellow researchers, and students to understand the applications of CE techniques in the impurity profiling of drugs.

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An overview of research related to the use of capillary electrophoresis in the impurity profiling of drugs is presented.

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The principle, instrumentation, and different types of capillary electrophoresis (CE) methods are outlined here.

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Applications of different of CE methods with the chemical structures of drugs and their impurities are highlighted.

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A brief description is also provided on the analysis of Pharmacopeial monographs using CE methods.

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A comparison of CE with liquid chromatography for impurity profiling and analysis of drugs is presented in this review.

Capillary electrophoretic methods for quality control analyses of pharmaceuticals: A review

Capillary electrophoresis represents a promising technique in the field of pharmaceutical analysis. The presented review provides a summary of capillary electrophoretic methods suitable for routine quality control analyses of small molecule drugs published since 2015. In total, more than 80 discussed methods are sorted into three main sections according to the applied electroseparation modes (capillary zone electrophoresis, electrokinetic chromatography, and micellar, microemulsion, and liposome-electrokinetic chromatography) and further subsections according to the applied detection techniques (UV, capacitively coupled contactless conductivity detection, and mass spectrometry). Key parameters of the procedures are summarized in four concise tables. The presented applications cover analyses of active pharmaceutical ingredients and their related substances such as degradation products or enantiomeric impurities. The contribution of reported results to the current knowledge of separation science and general aspects of the practical applications of capillary electrophoretic methods are also discussed.

Chiral Micellar Electrokinetic Chromatography

The potential of Micellar Electrokinetic Chromatography to achieve enantiomeric separations is reviewed in this article. The separation principles and the most frequently employed separation strategies to achieve chiral separations by Micellar Electrokinetic Chromatography are described. The use of chiral micellar systems alone or combined with other micellar systems or chiral selectors, as well as of mixtures of achiral micellar systems with chiral selectors is discussed together with the effect of different additives present in the separation medium. Indirect methods based on the derivatization of analytes with chiral derivatizing reagents and the use of achiral micelles are also considered. Preconcentration techniques employed to improve sensitivity and the main approaches developed to facilitate the coupling with Mass Spectrometry are included. The most recent and relevant methodologies developed by chiral Micellar Electrokinetic Chromatography and their applications in different fields are presented.

Comparison of a polymeric pseudostationary phase in EKC with ODS stationary phase in RP-HPLC

Poly(stearyl methacrylate-co-methacrylic acid) (P(SMA-co-MAA)) was induced as pseudostationary phase (PSP) in electrokinetic chromatography (EKC). The n-octadecyl groups in SMA were the same as that in octadecylsilane (ODS) C18 column. Thus, the present work focused on the comparison of selectivity between polymeric PSP and ODS stationary phase (SP), and the effect of organic modifiers on the selectivity of polymeric PSP and ODS SP. 1-butanol could directly interacted with PSP as a Class I modifier, and improved both of the methylene selectivity and polar group selectivity. When the analysis times were similar, the polymeric PSP exhibited better methylene selectivity and polar group selectivity. Although the hydrophobic groups were similar, the substituted benzenes elution order was different between polymeric PSP and ODS SP. Linear solvation energy relationships (LSER) model analysis found that polymeric PSP and ODS SP exhibited two same key factors in selectivity: hydrophobic interaction and hydrogen bonding acidity. But polymeric PSP exhibited relatively strong n- and π-electrons interaction to the analytes.

The effects of organic modifier on physicochemical and chromatographic characteristics of self-assembled micelle from poly (stearyl methacrylate-co-methacrylic acid) in electrokinetic chromatography

In our previous work, organic solvents, especially 1-butanol, play a key role to separate highly hydrophobic analytes in EKC using the polymeric micelle self-assembled from amphiphilic random copolymer poly (stearyl methacrylate-co-methyl acrylic acid) (P(SMA-co-MAA)) as a novel pseudostationary phase. Herein, the influences of organic solvents on polymeric micelle physicochemical properties including environmental micropolarity and dimension, as well as chromatographic characteristics containing elution window, hydrophobic selectivity and polar group selectivity were investigated in detail. P(SMA-co-MAA) has extremely low CMC of 1.26 × 10(-6) g/mL, and the self-assembled micelles with selective solvent method had regular spherical structure with diameter about 50 nm. The experimental results showed that methanol, isopropanol or acetonitrile molecules could not penetrate into the interior of the polymeric micelles, and mainly affected the properties of surrounding running buffer. Too much these organic solvents led to elution window narrowed down, methylene selectivity and group selectivity weaken, even the micelles collasped. Whereas, addition of 2% 1-butanol did not influence the elution window, instead, improved the hydrophobic selectivity. Furthermore, both better group selectivity and faster migration for relatively hydrophobic analytes could be achieved simultaneously. It indicated that 1-butanol could insert into the polymeric micelle and 2% 1-butanol was enough to modify the structure of the micelles.