Development and Validation of a Stability-Indicating LC Method for Determination of Bexarotene in Softgel Dosage Formulation

This study focuses on a novel liquid chromatographic approach that has been developed and approved for the quantitative determination of bexarotene (BXT), its potential impurities in drug substances and drug products. Chromatographic separation was developed on a Symmetry C₈ (150 × 4.6) mm 5-µm column with a mobile phase containing an isocratic mixture of acetonitrile:DI water:glacial acetic acid (650:350:7.5) v/v/v at a flow rate of 1.2 mL min^?1, and quantitation was carried out using ultraviolet detection at 262 nm for BXT and 290 nm for BHA with a column temperature of 35 °C. The resolution among butylated hydroxyanisole (BHA), BXT and its process-related impurity-A was found to be greater than 5. Regression analysis confers an R value (correlation coefficient) higher than 0.998 for BHA, BXT and impurity-A. The detection level for BXT impurities was found at a level below 0.03% (0.18 µg mL^?1). The inter- and intra-day precisions for BHA, BXT and impurities were evaluated and found to have a %RSD of less than 3.0.     

Novel simple fluorescent sensor for nickel ions

A novel pyrazoline with benzimidazole substituent was conveniently synthesized, starting from a chalcone and 2-hydrazinylpyridine. The addition of Ni²⁺ to ethanol solution of the synthesized pyrazoline resulted in a rapid color change from blue to green which allows the selective detection of Ni²⁺ ion over a great number of other metal ions. The association constant for the 1:1 complex was determined to be 2.72 × 10⁷ M^?1.     

Self-Assembly of Alkylammonium Chains on Montmorillonite: Effect of Interlayer Cations,CEC, and Chain Length

Recently, polymeric materials have been filled with synthetic or natural inorganic compounds in order to improve their properties. Especially, polymer clay nanocomposites have attracted both academic and industrial attention. Currently, the structure and physical phenomena of organoclays at molecular level are difficultly explained by existing experimental techniques. In this work, molecular dynamics (MD) simulation was executed using the CLAYFF and CHARMM force fields to evaluate the structural properties of organoclay such as basal spacing, interlayer density, energy and the arrangement of alkyl chains in the interlayer spacing. Our results are in good agreement with available experimental or other simulation data. The effects of interlayer cations (Na⁺, K⁺, Ca²⁺), the cation exchange capacity, and the alkyl chain length on the basal spacing and the structural properties are estimated. These simulations are expected to presage the microstructure of organo-montmorillonite and lead relevant engineering applications.