Separation and simultaneous estimation of enantiomers and Diastereomers of muscarinic receptor antagonist Solifenacin using stability-indicating Normal-phase HPLC technique with chiral stationary phase amylose tris-(3,5-dimethylphenylcarbamate).

The R,S-enantiomer impurity and diastereomer impurities (S,S-isomer and R,R-isomer) of the solifenacin (S,R-enantiomer) were effectively separated and quantified simultaneously utilizing normal-phase high-performance liquid chromatography with a chiral stationary phase consisting of amylose tris (3,5-dimethylphenylcarbamate) coated on silica-gel (Chiralpak, AD-H). The enantiomeric and stereo-selective separation was achieved within a run time of 35 minutes using a mobile phase of 'n-hexane, ethanol, and diethylamine' in an isocratic elution mode with a detection wavelength of 220 nm. The validation attributes assessed were accuracy (which showed excellent recoveries between 97.5% and 100.4%) and linearity (which was proven in the range of 0.081-1.275 µg.mL-1 , with a linear regression of 0.999). The stress testing experiments proved that the developed methodology by the HPLC technique has stability-indicating characteristics, as all closely eluting peak pairs were separated well with a resolution of 2.3 and without any interference. The proposed methodology was highly efficient in separating and simultaneously determining the chiral impurities (enantiomers and diastereomers) of the solifenacin in the release and stability sample analyses of drug substances and tablets in pharmaceutical formulations.

Separation and quantitative estimation of stereo-selective enantiomers of montelukast in pharmaceutical drug substance and tablets dosage forms by using stability-indicating normal phase-HPLC method.

Montelukast sodium (MLS) is a leukotriene receptor antagonist that relieves asthma, bronchospasm, allergic rhinitis, and urticaria. A simple, robust, and stability-indicating normal phase high-performance liquid chromatography method was developed to separate and quantitatively estimate the S-enantiomer of MLS. The chiral separation was achieved using USP L51 packing material along with a mobile phase consisting of a solvent mixture (n-hexane, ethanol, and propionic acid), a flow rate of 1.0 mL/min, a detection wavelength of 284 nm, a column temperature of 30°C and an injection volume of 20 µL. The enantiomers peaks were well separated from the peaks of the placebo, diluting solvent, MLS, and its known impurities with a resolution of more than 2.2 and with no interference. Accuracy and linearity were studied in a range of 0.36-3.597 µg/mL (0.03%-0.30%), with good recoveries between 92.5% and 96.8% and a linear regression coefficient above 0.996. The suggested chiral chromatography method is being considered as an alternative and equivalent method to the United States Pharmacopeia and European Pharmacopeia monographs. The developed method was effectively employed for the study of release and stability samples of MLS. This HPLC method is also capable of separating and estimating the stereo-selective isomers (R- and S-enantiomers) of sulfoxide impurity of MLS in pharmaceutical medicine.

Development and validation of liquid chromatography-tandem mass spectrometry method for the estimation of a potential genotoxic impurity 2-(2-chloroethoxy)ethanol in hydroxyzine.

2-(2-Chloroethoxy)ethanol (CEE) belongs to the so-called cohort of concerns which were classified as highly potent mutagenic carcinogens by the World Health Organization. It is widely used in the synthesis of the essential anti-histamine drug hydroxyzine. In addition, it is used as a primary solvent in dyes, nitrocellulose, paints, inks and resins. Owing to its potential genotoxicity, an efficient liquid chromatography-tandem mass spectrometry method was developed for the quantitative estimation of CEE traces in an active pharmaceutical ingredients and in tablet dosage forms of hydroxyzine-free base. The chromatographic separation was achieved on a C18 column using a gradient elution mode with a binary solvent system (ammonium formate and methanol). Mass detection was performed for CEE using a positive mode with selected ion monitoring technique at m/z value of [M + NH4 ]+ . The developed method was validated as per the International Conference on Harmonizaiton guidelines. The quantitation limit, linearity and recoveries were found to be 0.56 ppm, 0.56-7.49 ppm (r2 > 0.9985) and 93.6-99.3%, respectively. The proposed method was highly compatible and was used effectively to estimate CEE traces in different stages of drug synthesis and in tablet dosage forms of hydroxyzine for routine and stability testing.

[Impurity profile of macitentan in tablet dosage form using a stability-indicating high performance liquid chromatography method and forced degradation study].

Macitentan (MAC) is a pulmonary arterial hypertension (PAH) drug marketed as a tablet and often has stability issues in the final dosage form. Quantitative determination of MAC and its associated impurities in tablet dosage form has not been previously reported. This study quantified impurities present in Macitentan tablets using a binary solvent-based gradient elution method using reversed phase-high performance liquid chromatography. The developed method was validated per International Conference on Harmonization (ICH) guidelines and the drug product was subjected to forced degradation studies to evaluate stability. The developed method efficiently separated the drug and impurities (48 min) without interference from solvents, excipients, or other impurities. The developed method met all guidelines in all characteristics with recoveries ranging from 85%-115%, linearity with r2 ≥ 0.9966, and substantial robustness. The stability-indicating nature of the method was evaluated using stressed conditions (hydrolysis:1 N HCl at 80℃/15 min; 1 N NaOH at 25℃/45 min; humidity stress (90% relative humidity) at 25℃ for 24 h, oxidation:at 6% (v/v) H2O2, 80℃/15 min, thermolysis:at 105℃/16 h and photolysis:UV light at 200 Wh/m2; Fluorescent light at 1.2 million luxh). Forced degradation experiments showed that the developed method was effective for impurity profiling. All stressed samples were assayed and mass balance was>96%. Forced degradation results indicated that MAC tablets were sensitive to hydrolysis (acid and alkali) and thermal conditions. The developed method is suitable for both assay and impurity determination, which is applicable to the pharmaceutical industry.

Impurity profiling and a stability-indicating UPLC method development and validation for the estimation of related impurities of halobetasol propionate in halobetasol propionate 0.05% (w/w) cream.

A simple, short and stability-indicating reverse phase-ultra-performance liquid chromatography method was developed and validated for the quantitative determination of related impurities of halobetasol propionate in halobetasol propionate 0.05% cream formulation. The proposed method was developed on an ACQUITY UPLC™ BEH Phenyl (2.1 × 100 mm, 1.7 µm) column at 40°C with a mobile phase containing a gradient mixture of potassium hydrogen phosphate buffer and acetonitrile and methanol as modifiers with a runtime of 13.0 min at a monitored wavelength of 242 nm. A simple preparative method and liquid chromatography-mass spectrometry-compatible UPLC method also were developed for the isolation and identification of impurities and degradation products. The drug was subjected to forced-degradation conditions and found to degrade significantly. The stability-indicating capability of the developed method is established by analyzing forced-degradation samples in which the spectral purity of halobetasol propionate is ascertained along with the separation of degradation products from the analyte peak. The developed method was validated as per International Conference on Harmonization guidelines. The developed method is precise (%relative standard deviation <2.0) and is capable of detecting and quantifying all the six impurities at a level of 0.01 and 0.03%, respectively, with respect to test concentration. The wide linearity range, sensitivity, accuracy, short retention time and simple mobile phase imply that the method is suitable for routine quantification of halobetasol propionate and its related substances.