Selective formation of monodisperse spherical vaterite calcium carbonate (CaCO 3 ) precipitate using glycine (Gly) in a calcium hydroxide (Ca(OH) 2 )-carbon dioxide (CO 2 ) reaction system at room temperature and atmospheric pressure is reported. Crystalline products were examined by scanning electron microscopy, powder X-ray diffraction, Fourier transform infrared spectrometer, Raman spectra and laser particle size analysis. The experimental results suggest that increasing Gly concentration caused inhibition of the nucleation and growth of calcite and promoted the formation of vaterite. By adjusting the content of additive Gly, the crystalline product was almost monodisperse spherical vaterite CaCO 3 . The resulting product had good thermal stability, still keeping its crystal type, spherical shape, and size after being heated above 350°C. Mechanism studies illustrated that the complex effects between Gly and Ca 2+ played the key role in the formation process of monodisperse spherical vaterite CaCO 3 . Further studies indicated that this method might also apply to other reaction systems, such as CaCl 2 -NH 3 ·H 2 O-CO 2 and CaCl 2 -Na 2 CO 3 reaction systems. These studies are paving the way for industrial preparation and further commercial applications of monodisperse spherical vaterite CaCO 3 .
BackgroundA simple, rapid, and accurate stability-indicating reverse phase liquid chromatographic method was developed and validated for the simultaneous determination of pheniramine maleate and naphazoline hydrochloride in bulk drugs and pharmaceutical formulations.ResultsOptimum chromatographic separations among pheniramine maleate, naphazoline hydrochloride and stress-induced degradation products have been achieved within 10 minutes by using an Agilent zorbax eclipse XDB C18 column (150 mm × 4.6 mm, 5 μm) as the stationary phase with a mobile phase consisted of 10 mM phosphate buffer pH 2.8 containing 0.5% triethlamine and methanol (68:32, v/v) at a flow rate of 1 mL min-1. Detection was performed at 280 nm using a diode array detector. Theoretical plates for pheniramine maleate and naphazoline hydrochloride were calculated to be 6762 and 6475, respectively. The method was validated in accordance with ICH guidelines with respect to linearity, accuracy, precision, robustness, specificity, limit of detection and quantitation. Regression analysis showed good correlations (R2 > 0.999) for pheniramine maleate in the concentration range of 150–1200 μg mL-1 and naphazoline hydrochloride in 12.5-100 μg mL-1. The method results in excellent separation of both the analytes and degradation products. The peak purity factor is ≥980 for both analytes after all types of stress, indicating complete separation of both analyte peaks from the stress induced degradation products.ConclusionsOverall, the proposed stability-indicating method was suitable for routine quality control and drug analysis of pheniramine maleate and naphazoline hydrochloride in pharmaceutical formulations.
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