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The aim of the research was to verify that electrospraying of piroxicam yielded a new polymorphic form of this drug. In the experiments, piroxicam was dissolved in chloroform and the solution was atomised electrostatically. Subsequently, the charged droplets were neutralised and dried. The solid drug particles were collected and analysed by scanning electron microscopy, X-ray diffraction, differential scanning calorimetry, high performance liquid chromatography, and infrared and Raman spectroscopy. The X-ray diffractogram measured for the electrosprayed piroxicam particles did not match with any of the known piroxicam crystal structures ( Cambridge Crystallographic Data Centre ). The variable temperature X-ray diffraction showed that the structure recrystallised completely into piroxicam polymorphic form I during heating. No degradation products or solvate removal was detected by high performance liquid chromatography and thermal analysis. The infrared and Raman spectra of the electrosprayed piroxicam were compared to those of form I, and some notable differences in the peak positions, shapes and intensities were detected. The results indicate that electrospraying leads to piroxicam crystallisation in a currently unknown polymorphic form. [ABSTRACT FROM AUTHOR]

A potentiometric acid–base titration method was developed to characterize the acid–base properties of H-Beta-25, H-Beta-300, H-Ferrierite-20 and Si-MCM-48 zeolites in aqueous solutions. The method is based on linearization of the titration curve. The zeolite powders were dispersed in a sodium nitrate solution which was then titrated with a standard solution of sodium hydroxide. Various acid sites were found in the studied zeolites, and both the protonation constants and the concentrations of these acid sites were determined. The chemical composition (aluminum and silicon), distribution of the aluminum sites, crystallinity as well as the acidic properties of the titrated zeolites were compared with those of the pristine zeolites by using Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES), X-ray Diffraction (XRD), 27 Al NMR spectroscopy and the commonly used gas phase Fourier Transform Infrared spectroscopy (FTIR) of pyridine adsorption method. [ABSTRACT FROM AUTHOR]