Pudipeddi M, Sokoloski T D, Duddu S P, Carstensen J T
School of Pharmacy, University of Wisconsin, Madison 53706, USA.
J Pharm Sci. 1995 Oct;84(10):1236-9. doi: 10.1002/jps.2600841017.
The heat of precipitation of dl-pseudoephedrine was determined by direct calorimetry using a Tronac isoperibolic calorimeter. The precipitation of dl-pseudoephedrine was induced by mixing aqueous solutions of the two enantiomers, namely, d- and l-pseudoephedrine, directly in the calorimeter. The molar heat of precipitation of dl-pseudoephedrine was -2.7 and -3.0 kcal/mol at 25 and 30 degrees C, respectively. The aqueous solubility of dl-pseudoephedrine was determined over a temperature range of 20-40 degrees C. The van't Hoff solubility plot was nonlinear. The apparent heat of solution at saturation was obtained from the solubility data using a nonlinear regression model. A good agreement between the magnitude of the apparent heat of solution at saturation and the heat of precipitation was noticed at both 25 and 30 degrees C.
使用Tronac等压热量计通过直接量热法测定了消旋伪麻黄碱的沉淀热。消旋伪麻黄碱的沉淀是通过将两种对映体（即d-和l-伪麻黄碱）的水溶液直接在热量计中混合来诱导的。消旋伪麻黄碱在25℃和30℃下的摩尔沉淀热分别为-2.7和-3.0千卡/摩尔。在20-40℃的温度范围内测定了消旋伪麻黄碱的水溶性。范特霍夫溶解度曲线是非线性的。使用非线性回归模型从溶解度数据中获得饱和时的表观溶解热。在25℃和30℃时，均发现饱和时的表观溶解热大小与沉淀热之间有良好的一致性。
