Dissolution properties of calcined gangue

To study the dissolution mechanism of gangue, dissolution characteristics of the gangue samples calcined at different temperatures in alkaline solutions and alkali metal silicate solutions with respect to Si and Al ions were analyzed by identical coupled plasma optical emission spectroscopy （ICP）. The results show that the extent of dissolution of Al and Si varies with calcination temperature. It shows that the samples have a higher degree of dissolution in NaOH than in KOH medium. Si and Al appear to have synchro-dissolution behavior in alkaline solution, which means that Si and Al could dissolve from the mineral surface in certain linked forms. The result that a higher degree of dissolution exists in sodium silicate solution and a lower degree of dissolution exists in sodium-potassium silicate solution of Al is proved by the 29Si NMR spectra and the mean connectivity degree of these alkali metal silicate solutions.

Solubility and Thermodynamic Properties of Sulfamethazine-Saccharin Cocrystal in Pure and Binary (Acetonitrile + 2-Propanol) Solvents

In this work,a new crystallization method was used to prepare two polymorphs of sulfamethazine-saccharin(SMT-SAC)cocrystal in bulk.The purity and crystal form of both polymorphs were confirmed by optical microscopy,scanning electron microscopy,powder X-ray diff raction,diff erential scanning calorimetry,and thermogravimetric analysis.Moreover,the solubility of the stable form(form Ⅱ)was determined by gravimetric analysis in nine pure solvents and one binary(acetoni-trile+2-propanol)solvent at temperatures ranging from 278.15 to 348.15 K at atmospheric pressure.Experimental data were correlated using the modified Apelblat model,theλh equation,the nonrandom two-liquid(NRTL)model,the Jouyban-Acree model,and the CNIBS/Redlich-Kister model.Finally,the apparent thermodynamic properties,such asΔ_(dis)G,Δ_(dis) H,andΔ_(dis) S,were calculated on the basis of the activity coefficient obtained by the NRTL model.All the models correlate well,and all the experimental and calculated results indicate that the dissolution behavior of SMT-SAC cocrystal form II is a spontaneous,endothermic,and entropy-driven process.

Preparation and characterization of inclusion complexes of antitumor camptothecin with cucurbit[n=7,8]urils

The slightly water-soluble anticancer drug camptothecin(CPT) and its inclusion complexes with cucurbit[n = 7,8]uril(Q[n](n = 7,8)) were investigated.The formation of 1:2 complexes with Q[n](n = 7,8) in aqueous solution was confirmed by fluorescence spectroscopy and the apparent stability constants were determined to be higher than 3.01 × 1012 L2/mol2.The solid inclusion complexes of CPT and Q[n](n = 7,8) were also prepared by the co-evaporation method and characterized by Fourier transformation-infrared spectroscopy,differential scanning calorimetry and powder X-ray diffraction.Aqueous solubility and dissolution studies indicate that the complexes exhibited significantly increased dissolution rates compared with the pure drug and physical mixtures.The potential of Q[7] or Q[8] for stabilizing lactone modality of CPT was investigated by the High Performance Liquid Chromatography(HPLC) method.The results reveal more than 63% CPT lactone form(active form) in CPT-Q[7] or Q[8] complexes compared to only 36% CPT lactone form in the absence of Q[7] or Q[8] after being incubated in the phosphate buffer solution(pH 7.4 at 37 °C) for 5h.