DSC and IR as supporting tools for identification of methylxanthines in solid dosage forms of drugs

Abstract

The purpose of this study was to learn, to what extent the DSC, FT-IR and Raman spectroscopy can be useful for evaluation of the quality of medicinal products, the composition of marketed pharmaceutical preparations. As many as twenty-seven commonly available medicinal products were chosen, of which the majority constitute the so-called over-the-counter drugs. As basic active pharmaceutical ingredients (APIs), the products contained methylxanthines: theophylline, diprophylline and caffeine. The study has shown that in many cases the three techniques can be useful for the detection of APIs in medicinal products. To reach this aim, well-shaped endothermic DSC peaks, appearing due to melting of the active constituents and the so-called matching factors of the FT-IR and Raman spectra related to those of API used as standards, were utilised. The results obtained by Raman spectroscopy were satisfying to a limited extent only. On the other hand, the matching factors were twice less effective than the results obtained by the FT-IR technique. In the case of the preparations with caffeine, the matching factors were several times less effective than those obtained by FT-IR. An exception to this rule are only medicinal products containing acetylsalicylic acid, whose matching factors were several times higher than those of FT-IR, but because of their low concentrations, it was impossible to detect the ingredient in the sample.