Determination of the stereoisomeric impurities of sitafloxacin by capillary electrophoresis with dual chiral additives

A Practical Approach to Implementing ICH Q14: Tools for Analytical Quality by Design in Capillary Electrophoresis Method Development

The ICH Q14 guideline introduces a structured framework for analytical method development based on Analytical Quality by Design (AQbD) principles, aiming to ensure robust, reliable, and fit-for-purpose methods throughout the product lifecycle. However, implementing ICH Q14 remains challenging due to the lack of complete examples and training resources, making it difficult for organizations to translate theory into practice. Although previous studies have applied AQbD to capillary electrophoresis method development, many have focused only on specific aspects such as the design of experiments (DoEs) or analytical target profile (ATP), leaving a gap in providing comprehensive, practical tools for the entire analytical lifecycle. This manuscript presents a novel, user-friendly approach to implementing ICH Q14 and AQbD, offering ready-to-implement tools and methodologies that simplify the process of method design, optimization, validation, and implementation. Through a stepwise process, the approach provides practical solutions for integrating AQbD principles into everyday workflows, bridging the gap between theoretical concepts and real-world applications. The approach has been thoroughly tested in diverse industrial settings, demonstrating its reliability and effectiveness. This work aims to facilitate the adoption of AQbD in analytical method development by providing structured tools, lessons learned, and best practices that align with ICH Q14 guidelines.

Recent advances in chiral selectors immobilization and chiral mobile phase additives in liquid chromatographic enantio-separations: A review

For decades now, the separation of chiral enantiomers of drugs has been gaining the interest and attention of researchers. In 1991, the first guidelines for development of chiral drugs were firstly released by the US-FDA. Since then, the development in chromatographic enantioseparation tools has been fast and variable, aiming at creating a suitable environment where the physically and chemically identical enantiomers can be separated. Among those tools, the immobilization of chiral selectors (CS) on different stationary phases and the chiral mobile phase additives (CMPA) which have been progressed and studied extensively. This review article highlights the major advances in immobilization of CS together with their different recognition mechanisms as well as CMPA as a cheaper and successful alternative for chiral stationary phases. Moreover, the role of molecular modeling tool as a pre-step in the choice of CS for evaluating possible interactions with different ligands has been pointed up. Illustrations of reported methods and updates for immobilized CS and CMPA have been included.

Copper (II) Ions Induced Self-Disproportionation of Enantiomers in Capillary Electrophoresis for the Quantification of Atenolol Enantiomers

Despite the fact that the self-disproportionation of enantiomers (SDE) has been found for several decades and has been widely used in crystallization, sublimation and chromatography for the purification or separation of nonracemic compounds, the phenomenon of SDE in capillary electrophoresis (CE) has never been reported up to now. Here, a new approach to separate enantiomers in CE based on SDE was demonstrated by introducing copper (II) ions into the separation media. The enantiomers of atenolol interact with copper ions to produce positively charged complexes with different electrophoretic mobilities from the single molecules. The dynamic equilibrium between homo- or heterochiral complexes (associates) and single molecules of atenolol enantiomers supports the manifestation of SDE. Different mobilities of the single molecules and associates, and different distribution of two enantiomers between the single molecules and associates caused by their different concentrations, produce a net difference in electrodriven migration velocities of the two enantiomers. The relative movement of two enantiomers causes a zone depleted in one enantiomer at the rear end of sample segment, giving a trapezoidal CE curve with a step at the end. Quantification of enantiomers is achieved according to the step height. The analysis does not rely on the use of enantiomerically pure chiral selector and the result agrees with that obtained by conventional chiral CE using a chiral selector.

New Trends in the Quality Control of Enantiomeric Drugs: Quality by Design-Compliant Development of Chiral Capillary Electrophoresis Methods

Capillary electrophoresis (CE) is a potent method for analyzing chiral substances and is commonly used in the enantioseparation and chiral purity control of pharmaceuticals from different matrices. The adoption of Quality by Design (QbD) concepts in analytical method development, optimization and validation is a widespread trend observed in various analytical approaches including chiral CE. The application of Analytical QbD (AQbD) leads to the development of analytical methods based on sound science combined with risk management, and to a well understood process clarifying the influence of method parameters on the analytical output. The Design of Experiments (DoE) method employing chemometric tools is an essential part of QbD-based method development, allowing for the simultaneous evaluation of experimental parameters as well as their interaction. In 2022 the International Council for Harmonization (ICH) released two draft guidelines (ICH Q14 and ICH Q2(R2)) that are intended to encourage more robust analytical procedures. The ICH Q14 guideline intends to harmonize the scientific approaches for analytical procedures' development, while the Q2(R2) document covers the validation principles for the use of analytical procedures including the recent applications that require multivariate statistical analyses. The aim of this review is to provide an overview of the new prospects for chiral CE method development applied for the enantiomeric purity control of pharmaceuticals using AQbD principles. The review also provides an overview of recent research (2012-2022) on the applicability of CE methods in chiral drug impurity profiling.

Application of Experimental Design Methodologies in the Enantioseparation of Pharmaceuticals by Capillary Electrophoresis: A Review

Chirality is one of the major issues in pharmaceutical research and industry. Capillary electrophoresis (CE) is an interesting alternative to the more frequently used chromatographic techniques in the enantioseparation of pharmaceuticals, and is used for the determination of enantiomeric ratio, enantiomeric purity, and in pharmacokinetic studies. Traditionally, optimization of CE methods is performed using a univariate one factor at a time (OFAT) approach; however, this strategy does not allow for the evaluation of interactions between experimental factors, which may result in ineffective method development and optimization. In the last two decades, Design of Experiments (DoE) has been frequently employed to better understand the multidimensional effects and interactions of the input factors on the output responses of analytical CE methods. DoE can be divided into two types: screening and optimization designs. Furthermore, using Quality by Design (QbD) methodology to develop CE-based enantioselective techniques is becoming increasingly popular. The review presents the current use of DoE methodologies in CE-based enantioresolution method development and provides an overview of DoE applications in the optimization and validation of CE enantioselective procedures in the last 25 years. Moreover, a critical perspective on how different DoE strategies can aid in the optimization of enantioseparation procedures is presented.

An appraisal of experimental designs: Application to enantioselective capillary electromigration techniques

Enantioresolution processes are vital tools for investigating the enantioselectivities of chiral compounds. An analyst resolves to optimize enantioresolution conditions once they are determined. Generally, optimization is conducted by a one-factor-at-a-time (OFAT) approach. Although this approach may determine an adequate condition for the method, it does not often allow the estimation of the real optimum condition. Experimental designs are conducive for the optimization of enantioresolution methods via capillary electromigration techniques (CETs). They can efficiently extract information from the behavior of a method and enable the estimation of the real optimum condition. Furthermore, the application of the analytical quality by design (AQbD) approach to the development of CET-based enantioselective methods is a trend. This article (i) offers an overview of the application of experimental designs to the development of enantioselective methods from 2015 to mid-2020, (ii) reveals the experimental designs that are presently employed in CET-based enantioresolutions, and (iii) offers a critical point of view on how the different experimental designs can aid the optimization of enantioresolution processes by considering the method parameters.

Advances of capillary electrophoresis enantioseparations in pharmaceutical analysis (2017-2020)

Capillary electrophoresis is a powerful technique for the analysis of polar chiral compounds and has been widely accepted for analytical enantioseparations of drug compounds in pharmaceuticals and biological media. In addition, many mechanistic studies have been conducted in an attempt to rationalize enantioseparations in combination with spectroscopic and computational techniques. The present review will focus on recent examples of mechanistic aspects and summarize recent applications of stereoselective pharmaceutical and biomedical analysis published between January 2017 and November 2020. Various separation modes including electrokinetic chromatography in combination with several detection modes including laser-induced fluorescence, mass spectrometry and contactless conductivity detection will be discussed. A general trend also observed in other analytical techniques is the application of quality by design principles in method development and optimization.

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.

Combined Use of Cu(II)-L-Histidine Complex and β-Cyclodextrin for the Enantioseparation of Three Amino Acids by CE and a Study of the Synergistic Effect

A new capillary electrophoresis method was applied to chiral separation of three amino acids, including D,L-tryptophan, D,L-tyrosine and D,L-phenylalanine. The chiral resolution was attained in an untreated fused-sillica capillary using a dual chiral selector, which was made up of Cu(II)-L-histidine complex and β-cyclodextrin (CD). The cardinal factors influencing its separation efficiency, such as chiral selectors, buffer pH and applied voltage, were optimized. Best results were acquired by using a buffer consisting of 10 mmol/L Cu(II), 13 mmol/L L-histidine, 8 mmol/L β-CD, 5 mmol/L phosphate adjusted to pH 5.0 and 15 kV applied voltage. All enantiomers were entirely resolved within 20 min with high resolutions of 3.6~6.1. The analysis method was verified through the determination of D,L-tryptophan in terms of linearity, precision and accuracy. And the robustness of this method was proved. The Limit of Detection and Limit of Quantification for both enantiomers were 2.5 and 5 μg/mL, respectively. The method was perfectly applied to the determination of the enantiomeric purity of L-tryptophan. Furthermore, the interaction between Cu(II)-L-histidine complex and β-CD was also studied using Ultraviolet-visible and 1H NMR spectroscopy to explain the synergistic effect involved. The results illustrated that Cu(II)-L-histidine complex and β-CD played a synergistic role in the enantiomeric separation of chiral drugs, with good prospects for application.

Chiral Selectors in Capillary Electrophoresis: Trends During 2017⁻2018

Chiral separation is an important process in the chemical and pharmaceutical industries. From the analytical chemistry perspective, chiral separation is required for assessing the fit-for-purpose and the safety of chemical products. Capillary electrophoresis, in the electrokinetic chromatography mode is an established analytical technique for chiral separations. A water-soluble chiral selector is typically used. This review therefore examines the use of various chiral selectors in electrokinetic chromatography during 2017–2018. The chiral selectors were both low and high (macromolecules) molecular mass molecules as well as molecular aggregates (supramolecules). There were 58 papers found by search in Scopus, indicating continuous and active activity in this research area. The macromolecules were sugar-, amino acid-, and nucleic acid-based polymers. The supramolecules were bile salt micelles. The low molecular mass selectors were mainly ionic liquids and complexes with a central ion. A majority of the papers were on the use or preparation of sugar-based macromolecules, e.g., native or derivatised cyclodextrins. Studies to explain chiral recognition of macromolecular and supramolecular chiral selectors were mainly done by molecular modelling and nuclear magnetic resonance spectroscopy. Demonstrations were predominantly on drug analysis for the separation of racemates.

Experimental Design Methodologies for the Optimization of Chiral Separations: An Overview

In this chapter, the application of design of experiments (DoE) for chiral separation optimization using supercritical fluid chromatography (SFC), liquid chromatography (LC), capillary electrophoresis (CE), and capillary electrochromatography (CEC) methods is reviewed. Both screening and optimization steps are covered, including a discussion of each aspect, such as factor-, level-, and response selection. Different designs are also presented, highlighting their applications.