Authors:Marek Wesolowski, Piotr Szynkaruk, and Edyta Makurat
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.
Authors:Piotr Szynkaruk, Marek Wesolowski, and Malgorzata Samson-Rosa
Thermal decomposition of magnesium salts of organic acids used in medicine (Mg acetate, Mg valproate, Mg lactate, Mg citrate,
Mg hydrogen aspartate, Zn hydrogen aspartate) was analyzed by thermoanalytical, calorimetrical, and computational methods.
Thermoanalytical studies were performed with aid of a derivatograph. 50-, 100-, and 200-mg samples were heated in a static
air atmosphere at a heating rate of 3, 5, 10, and 15 °C min−1 up to the final temperature of 700–900 °C. By differential thermal analysis (DTA), thermogravimetry (TG), and derivative
thermogravimetry (DTG) methods, it has been established that thermal decomposition of the salts under study occurs via two
stages. The first stage (dehydratation) was distinctly marked on the thermoanalytical curves. Calorimetrical studies were
carried out by using of a heat-flux Mettler Toledo differential scanning calorimetry (DSC) system. Ten milligram samples of
compounds under study were heated in the temperature range from 20 to 400 °C at a heating rate of 10 and 20 °C min−1 under an air stream. The studies showed that the values of transitions heats and enthalpies of dehydration for investigated
salts varied with the increasing of heating rate. For chemometric evaluation of thermoanalytical results, the principal component
analysis (PCA) was applied. This method revealed that points on PC1 versus PC2 diagrams corresponding to the compounds of
similar chemical constitution are localized in the similar ranges of the first two PC’s values. This proves that thermal decomposition
reflects similarity in the structure of magnesium salts of organic acids.