Principal component analysis of thermal decomposition of magnesium salts used as drugs

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.     

Thermal decomposition of methylxanthines

The thermal decomposition of theophylline, theobromine, caffeine, diprophylline and aminophylline were evaluated by calorimetrical, thermoanalytical and computational methods. Calorimetrical studies have been performed with aid of a heat flux Mettler Toledo DSC system. 10 mg samples were encapsulated in a 40 μL flat-bottomed aluminium pans. Measurements in the temperature range form 20 to 400°C were carried out at a heating rate of 10 and 20°C min⁻¹ under an air stream. It has been established that the values of melting points, heat of transitions and enthalpy for methylxanthines under study varied with the increasing of heating rate. Thermoanalytical studies have been followed by using of a derivatograph. 50, 100 and 200 mg samples of the studied compounds 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 800°C. By DTA, TG and DTG methods the influence of heating rate and sample size on thermal destruction of the studied methylxanthines has been determined. For chemometric evaluation of thermoanalytical results the principal component analysis (PCA) was applied. This method revealed that first of all the heating rate influences on the results of thermal decomposition. The most advantageous results can be obtained taking into account sample masses and heating rates located in the central part of the two-dimensional PCA graph. As a result, similar data could be obtained for 100 mg samples heated at 10°C·min⁻¹ and for 200 mg samples heated at 5°C min⁻¹.     

Thermal Decomposition of Purine Derivatives Used in Medicine

Thermal decomposition of several purine derivatives used in medicine –theophylline, theobromine, caffeine, diprophylline and aminophylline was investigated. The analyses were performed using a derivatograph. It has been established, that the thermal decomposition of purine derivatives occurs via three stages. The stages of dehydratation of hydrate and evaporation of aminophylline are distinctly marked on the thermoanalytical curves, which may be used for the control of composition of the studied compounds. The ranges of temperature, in which the analyzed compounds can be technologically transformed without change of their physicochemical properties, were also established. Moreover, the influence of heating rate and sample size on the thermal decomposition of the examined compounds was evaluated. This revised version was published online in July 2006 with corrections to the Cover Date.     

Detection of magnesium compounds in dietary supplements and medicinal products by DSC,Infrared and Raman techniques

The aim of this study was to learn to what extent the selected instrumental techniques, differential scanning calorimetry (DSC), as well as Fourier-transform infrared (FTIR) and Raman spectroscopies, can be used to detect both organic or inorganic magnesium compounds in the dietary supplements and medicinal products. Besides magnesium compounds as the active pharmaceutical ingredients (APIs), the preparations contain also other organic and inorganic APIs and several excipients. The study will be extended over the analysis of the products manufactured by various firms but containing the same API at different levels. In this way, it will be possible to assess the impact of excipients on the DSC scans and the FTIR and Raman spectra of a dominant constituent present in a studied preparation. The study on thirty commercially available dietary supplements and medicinal products has shown that in the majority of cases the DSC, FTIR and Raman techniques could be used for the detection of APIs in these commercial products. This was possible with the aid of the endothermic DSC peaks and the so-called matching factors of the FTIR and Raman spectra to those of substances used as standards. Both the complex composition and low levels of API in the studied preparations have been identified as the factors which have a strong impact on the usefulness of the three techniques for the detection of APIs in the dietary and medicinal products.