Polysaccharide and Cyclodextrin-Based Monolithic Chiral Stationary Phases and its Application to Chiral Separation.

The recent development of monolithic chiral stationary phases (CSPs) for liquid chromatography (LC) is mainly focused on reducing backpressure, maximizing flow rates, faster run time, column efficiency, and stability. This review paper emphasizes recent progress in the development of polysaccharide and cyclodextrin-based monolithic CSPs. Further the paper draws attention to competing techniques, like non-porous particle-packed columns, core-shell and monoliths as chromatographic support matrix, available for achieving fast and efficient chromatographic separation. A brief discussion on the three main classes of chiral monolithic stationary phase viz. silica, organic polymer and hybrid-based monolithic stationary phases is also presented. In addition, the paper highlights various studies on the application of monolith chiral CSPs in LC and capillary electrochromrography separation and analysis of chiral compounds.

Chiral Inversion of Pharmaceutical Drugs - Mini Review.

2-Arylpropionic acid nonsteroidal anti-inflammatory drugs (NSAIDs) provide one of the most demonstrated pharmaceutical examples of chiral inversion. Chiral inversion depends on various factors (viz. biological-, solvent-, light-, temperature-induced, etc.) and the energy barrier associated with the stereogenic element present in the chiral molecule. The pharmacological properties of chiral drugs depend on the activity of one enantiomer or both the enantiomers targeting different biological targets. Consequently, chiral inversion can alter the biological activities of the pharmaceutical drug. Hence a better understanding of chiral inversion, factors facilitating such inversion, and the tools employed to determine chiral inversion are of great significance from a pharmacological and toxicological perspective.

Impact of cyclofructan derivatives as efficient chiral selector in chiral analysis: An overview.

The development of chiral selectors for the separation and analysis of chiral molecules has been an evolving process happening over three decades, since the introduction of the first chiral stationary phase (CSP) in 1938. The main impetus for designing new chiral selectors is to get to most promising one which has a broad chiral recognition property, separation capability for a wide range of chiral analytes, and the cost-effective CSP, which is also a major concern. Today, we have more than 100 commercially available CSPs, and these are prepared by coating or immobilizing the classical chiral selectors on to the chromatographic support, normally, silica gel. The purpose of this review is to look at progress and the impact of cyclofructan derivatives, a novel chiral selector introduced recently, for performing chiral analysis.

D-Optimal mixture design optimization of an HPLC method for simultaneous determination of commonly used antihistaminic parent molecules and their active metabolites in human serum and urine.

This study describes a specific, precise, sensitive and accurate method for simultaneous determination of hydroxyzine, loratadine, terfenadine, rupatadine and their main active metabolites cetirizine, desloratadine and fexofenadine, in serum and urine using meclizine as an internal standard. Solid-phase extraction method for sample clean-up and preconcentration of analytes was carried out using Phenomenex Strata-X-C and Strata X polymeric cartridges. Chromatographic analysis was performed on a Phenomenex cyano (150 × 4.6 mm i.d., 5 µm) analytical column. A D-optimal mixture design methodology was used to evaluate the effect of changes in mobile phase compositions on dependent variables and optimization of the response of interest. The mixture design experiments were performed and results were analyzed. The region of ideal mobile phase composition consisting of acetonitrile-methanol-ammonium acetate buffer (40 mm; pH 3.8 adjusted with acetic acid): 18:36:46% v/v/v was identified by a graphical optimization technique using an overlay plot. While using this optimized condition all analytes were baseline resolved in <10 min. Solvent mixtures were delivered at 1.5 mL/min flow rate and analytes peaks were detected at 222 nm. The proposed bioanalytical method was validated according to US Food and Drug Administration guidelines. The proposed method was sensitive with detection limits of 0.06-0.15 µg/mL in serum and urine samples. Relative standard deviation for inter- and intra-day precision data was found to be <7%. The proposed method may find application in the determination of selected antihistaminic drugs in biological fluids.

Simultaneous enantioseparation and purity determination of chiral switches of amlodipine and atenolol by liquid chromatography.

A novel, selective and robust enantiospecific HPLC method was developed for simultaneous determination of amlodipine and atenolol enantiomers. Box-Behnken design was employed to identify the effect of factors (% ethanol, % diethylamine and flow rate) and their interactions on enantioresolution and analysis time. Chromatography was performed using mobile phase comprising acetonitrile, ethanol and DEA (92:8:0.2% v/v/v) delivered at a flow rate of 1.2mLmin(-1) on a Lux Cellulose-4 column. The enantiomers were monitored at a wavelength of 240nm and separation was achieved within 8min. The method was validated in terms of specificity, linearity, accuracy, precision, limit of detection and quantification. The method was found to be linear (R(2)≥0.991), accurate (99.8-101.4%) and precise (%RSD≤3%). Additionally, fractional factorial design was used to evaluate the robustness of the method and non-significant intervals for mixture related factors were established using contour profiling. Furthermore, the pertinence of this validated method was established by analyzing three different commercially available formulations. The obtained results confirmed that the proposed method can be extended for routine enantiopurity assay of amlodipine and atenolol in pharmaceutical formulations.

Multiple response optimization of a liquid chromatographic method for determination of fluoroquinolone and nitroimidazole antimicrobials in serum and urine.

OBJECTIVES: Development and validation of a sensitive, selective and robust SPE assisted HPLC method for the quantification of fluoroquinolones and nitroimidazoles in human serum and urine using design of experiments methodology. DESIGN AND METHODS: Design of experiments was employed for method optimization (Box-Behnken design) and robustness testing (Plackett-Burman design). Sample preparation involved a simple solid phase extraction, which offered a satisfactory recovery (≥94%). Analytes were separated on a phenyl hexyl column with mobile phase comprising water, acetonitrile and triethyl amine in ratio of 74:26:0.15 v/v, with a flow rate of 1.1mL/min. RESULTS: Calibration curves were linear over selected range (≥0.995) for all the analytes. The method was sensitive with detection limits of 0.06-0.16µg/mL in serum and urine samples. Inter and intra-day precision data (in terms of %RSD) was found to be less than 7%. Stability studies were carried out to assess freeze thaw, short term and long term stability and all analytes were found to be stable. The method was successfully applied for determination of antimicrobial drugs in spiked serum and urine. CONCLUSION: The obtained results corroborated the potential of the proposed method for determination of all the four antimicrobial drugs in therapeutic drug monitoring, bioequivalence and drug-drug interaction studies.

Systematic Robustness Testing of a Liquid Chromatographic Method: A Case Study.

Robustness testing of a method plays a crucial role in establishing its reliability. It examines the potential sources of variability in one or more responses of the proposed method. In this study, the robustness testing of a method proposed for simultaneous determination of warfarin and its two process related impurities was evaluated by using two level, fractional factorial design. Factors that are sensitive to a variation during method transfer were selected as independent variables [aqueous content (range: 39-43%, v/v), concentration of acetic acid (range: 0.08-0.12%, v/v), flow rate (range: 0.93-1.33 mL/min), and wavelength (range: 218-222 nm)]. Variables that determine the quality of separation, viz., retention factor of the first peak, resolution between the critical peak pair, tailing factor of warfarin, and total analysis time were selected as responses. Robustness was assessed by graphical (half normal probability and Pareto plots) and statistical (analysis of variance) methods. It was found that, among the studied variables, aqueous content had a significant effect on capacity factor and analysis time. Furthermore, non-significant intervals for significant factors were established by contour profiling. This study demonstrated the significance of experimental design and other statistical tools in understanding the effects of investigating factors of the chromatographic system and in defining their limits.