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Combined PAT-solid state analytical approach for the detection and study of sodium benzoate hydrate
journal contributionposted on 14.07.2009, 13:52 by Krystel S. Howard, Zoltan Nagy, Basu Saha, Anne L. Robertson, G. Steele
This paper presents the application of process analytical technology (PAT) tools in combination with solid state analytical (SSA) techniques for the detection of solvent-mediated pseudopolymorphic transformations and the discovery of a new hydrate form of the model system, sodium benzoate in water. Cooling crystallization experiments were performed at a range of scales including 1 mL, 250 mL, and 1 L, using turbidity and focused beam reflectance measurement (FBRM) probes. The solubility determination using the turbidity probe indicated a very low solubility of the sodium benzoate crystals in organic solvents but high solubility in water, with low temperature sensitivity in all cases, making the control of cooling crystallization challenging. Monitoring the cooling crystallization of sodium benzoate from water using focused beam reflectance measurement (FBRM) probe indicated the formation of sodium benzoate hydrate, which has not been reported before. Additionally, a combination of off-line solid state techniques were used, including optical and scanning electron microscope (SEM), hot stage microscopy (HSM), X-ray powder diffraction (XRPD), nuclear magnetic resonance (NMR) spectroscopy, infrared (IR) spectroscopy, differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA) and dynamic vapour sorption (DVS), to confirm the formation of the new channel hydrate, when sodium benzoate recrystallizes from water.
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