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Hydrochlorothiazide (HCT) is a diuretic drug with poor solubility and permeability. Physicochemical properties of HCT have been modified by cocrystallization with piperazine (PPZ), tetramethylpyrazine (TMPZ), picolinamide (PCM), isoniazid (INZ), malonamide (MAM), and isonicotinic acid (INIC) using mechanochemical grinding (liquid assisted and neat). The solids obtained were characterized by single crystal X-ray diffraction (SCXRD), powder X-ray diffraction, Fourier transform infrared spectroscopy, and differential scanning calorimetry and subjected to solubility and membrane permeability studies. SCXRD showed that the N-H···O sulfonamide catemer synthons found in the stable polymorph of pure HCT have been replaced by drug-coformer heterosynthons in the cocrystals. HCT-PPZ and HCT-PCM cocrystals showed improvement in solubility and membrane permeability/diffusion compared to the parent active pharmaceutical ingredient. The improved solubility and diffusion rates are due to the drug-coformer interactions in the new solid forms. A structure-property relationship is examined to evaluate the solubility and diffusion rates of the new solid forms. The cocrystal with INIC, which could not be prepared previously by conventional methods, was obtained by prolonged grinding for 6 days. Hydrochlorothiazide is a diuretic drug, often used to treat high blood pressure and swelling due to fluid buildup. New solid forms of hydrochlorothiazide (HCT) were made using coformers. HCT-piperazine (PPZ) and HCT-picolinamide (PCM) cocrystals showed improved solubility and membrane diffusivity compared to the parent active pharmaceutical ingredient. The improved physicochemical properties are due to the drug-coformer interactions in the new solid forms. [ABSTRACT FROM AUTHOR]

Phase transition from vaterite to calcite is a general behavior of CaCO3materials. The effect of nitrilotriacetic acid disodium salt (NTA) on the crystallization behavior and polymorphism of CaCO3was studied at different temperatures between 60 and 230°C. The morphologies and the structure of the precipitates were characterized using scanning electron microscope, field emission scanning electron microscopy, powder X-ray diffraction, Raman spectroscopy, and Fourier transform infrared spectroscopy. It was observed that NTA could change the morphologies and crystal structures of CaCO3with temperature and stabilize least stable vaterite at high temperature. An anomalous conversion of calcite to vaterite in the presence of NTA was observed. The effect of amount of NTA added on the crystallization behavior at selected temperatures is reported. [ABSTRACT FROM PUBLISHER]

Abstract: CaCO3 was crystallized from CaCl2 solution containing commercially available 1-hydroxyethylidene-1,1-diphosphonic acid, Aqua soft having a chelating value of 330 (AS 330). The effect of the concentration of AS 330 and the temperature of crystallization on the morphology and crystalline structure of CaCO3 was investigated. The samples were characterized using scanning electron microscopy (SEM), powder X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The presence of AS 330 favored ternary calcite–vaterite–aragonite mixture at 60 and 80°C and a binary calcite–vaterite mixture at 100°C. Rhomboidal calcite, needle/rod like aragonite and flower like vaterite were obtained under different conditions. In contradiction to the usual process of the transformation of amorphous CaCO3 into different polymorphic forms, the data confirmed calcite is the precursor for the flower structured vaterite. The mechanism of formation of the flower structured vaterite is discussed in detail. [Copyright &y& Elsevier]

Abstract: Crystallization behavior and polymorphism of CaCO3 were studied at different temperatures (from 60 to 240°C) under the influence of ethylenediaminetetraacetic acid (EDTA). The samples were characterized using powder X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), Scanning electron microscope (SEM) and field emission scanning electron microscopy (FESEM). In the absence of EDTA, a calcite–aragonite binary mixture was resulted between 60 and 170°C above which calcite alone was formed. The presence of EDTA significantly influenced the crystallization behavior and composition of different polymorphs of CaCO3 varied with temperature. Formation of a binary calcite–aragonite mixture at 60°C, ternary calcite–vaterite–aragonite mixture at 100°C, a binary aragonite–vaterite mixture at 130°C, a binary calcite–aragonite mixture at 170°C, purely aragonite at 200°C and vaterite with very little aragonite at 230°C confirmed that temperature affects the crystallization process in the presence of EDTA. Rhomboidal calcite, needle/rod like aragonite and flower like vaterite were obtained under different conditions. At 230°C, a unique flower like morphology was observed for vaterite. The efficacy of EDTA on CaCO3 scale inhibition between 60 and 230°C is discussed. [Copyright &y& Elsevier]