(344f) Influence of the Composition of Water/Methanol Mixtures and Temperature on the Crystal Form and Solubility of Sodium Dehydroacetate

The slurry transformation experiments for the monohydrate of sodium dehydroacetate with different compositions of water and methanol at varying temperatures were investigated in this study. It was found that the temperature and water content affected not only the solubility but also the crystal form of the precipitated material. The sodium dehydroacetate anhydrate was obtained with a low water content; however, the monohydrate of sodium dehydroacetate was the more stable form with a high water content. At the same time, the solubility of anhydrate and monohydrate of sodium dehydroacetate were measured with different compositions and temperatures. From powder X-ray diffractionï¼?PXRDï¼?patterns, thermal gravimetric analysis (TGA) data and scanning electron microscopy (SEM), a new needle hydrate form of sodium dehydroacetate was shown on the surface of anhydrous phase when the water content was between 2 % and the critical transformation values. In situ Raman spectra and microscope images demonstrated that this needle hydrate was not the metastable intermediate nor was it the result of concomitant crystallization during the transformation. Pure needle hydrate of sodium dehydroacetate was obtained using evaporation crystallization. Moreover, the PXRD patterns and TGA results revealed that this needle hydrate was another new form of sodium dehydroacetate monohydrate. A possible explanation for these observations was found in the relationship between the change of water content, the interaction between solute and solvent and the influence of supersaturation.