Determining water content and other impurities in <i>Siparuna guianensis</i> Aublet essential oil using differential scanning calorimetry

Abstract

Siparuna guianensis Aublet is a predominant species in the Brazilian Cerrado. Some studies found that its essential oil has properties that could be useful for manufacturing new products. Its quality depends on physicochemical properties, since its degradation, as well as water content and other volatile materials may cause several changes in its features. The differential scanning calorimetry (DSC) was used to determine the water content in the S. guianensis essential oil in order to evaluate its thermal parameters. The method is based on the hypothesis that the desolvation enthalpy (ΔH_desol) needed for removing n water moles from the essential oil is approximately the enthalpy needed for melting the same n water moles (nΔH_f). Thus, the current study considers the dissociation enthalpy (ΔH_diss) to be negligible. The total number of moles was calculated from the molecular mass value of the main essential oil components mentioned in the literature. The DSC curve in nitrogen atmosphere indicated the melting temperature of 1.6°C (ΔH=18.95 Jg^-1). Based on the dehydration enthalpies demonstrated in the DSC curve, it was possible to infer that the calculations on the number of water moles and other constant volatile materials found in the S. guianensis essential oil were compatible with Karl Fischer Titration (KFT) method. This method is commonly used to determine the water content in substances.

Key words: Siparuna guianensis, differential scanning calorimetry, thermogravimetric analyses.