Methods of the matrix analysis and graphic ranking of the array of the experimental IR spectroscopy data in studying the inter-component processes in the mixture of pheniramine maleate and naproxen

Abstract

A widespread use of complex pharmacotherapy entails the necessity of studying the processes occurred in pharmaceutical mixtures. IR spectroscopy is one of the methods used to assess the stability of substances. To increase the efficiency of interpretation of the IR spectra of mixtures, a method combining matrix methods and graphic ranking of the array of experimental data has been developed. This approach has been tested for the analysis of model mixtures of pharmaceutical substances naproxen and pheniramine maleate. Absorption spectra were obtained on an Avatar 360 FT-IR ESP Fourier transform spectrometer (Nicolet, USA) using an ATR (primary attenuation total reflection) attachment Smart Perfbmer (optical crystal ZnSe; spectral range 1.35 - 26.6 pm, 7400 - 375 cm4). The obtained IR spectra were processed using Thermo Scientific Specta embedded software. Graphs for graphical ranking were plotted in the coordinates of the mixture heating temperature —relative frequency intensity. The points on the graph represent the relative intensity of the bands for a mixture kept at a certain temperature, whereas the curves with which they are connected reflect the processes occurring in the structure of the substance. Common trends in the relative intensity for different frequencies (at the same temperature) and/or for a number of frequencies of a certain characteristic region, indicates the unidirectionality of the process. Graphic ranking is applied to the characteristic bands of pyridine and aliphatic nitrogen of pheniramine maleate and characteristic frequencies of the intermolecular hydrogen bond and carbonyl group of naproxen. We also used the method of mathematical ranking of the matrices of transmittance values. For the characteristic bands of the studied compounds, a combined use of graphical and mathematical ranking allowed us to infer a change in the structure of naproxen and pheniramine maleate under the impact of elevated temperatures: the salt of pheniramine and maleic acid in aliphatic nitrogen has one structural conformation, whereas the binding force depends on the temperature.