School of Pharmacy, University of Otago, PO Box 56, Dunedin, New Zealand.
Int J Pharm. 2012 Jan 17;422(1-2):68-74. doi: 10.1016/j.ijpharm.2011.10.028. Epub 2011 Oct 20.
Coalescence of polymer particles on thermal treatment plays an important role in effective control of drug release from these matrix systems. The water content of the polymer may influence coalescence since it is well established that sorbed water may act as a plasticizer, or cause other changes in mechanical properties. However, these effects depend on the amount and type (plasticizing/nonplasticizing) of water present. The purpose of this study was to determine the accuracy of different methods used to determine moisture content of a polymer (Eudragit RLPO) and to determine the types water present. The polymer powder was stored at various relative humidities (33, 56, 75, 94%). Four water determination methods, [weight loss on drying, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and Karl Fischer titration (KFT)] were utilized to determine moisture content. DSC was used to study the thermal behaviour of moist and dry samples. The Gordon-Taylor equation was used to calculate the amount of plasticizing water. Scanning electron microscopy was employed to examine the morphology of the polymer particles after thermal analyses. It is concluded that KFT accurately determines the total water content but that the thermal methods underestimate total water content. However KFT does not indicate the type of water present. The Gordon-Taylor model suggests that only about 25% of the water in the polymer containing 10% water was acting as a plasticizer. Complementary methods should be used to measure the water content of pharmaceutical polymers.
聚合物颗粒在热处理过程中的聚集对于有效控制这些基质系统中药物的释放起着重要作用。聚合物的含水量可能会影响聚集，因为已经确定吸附水可以作为增塑剂，或者导致机械性能的其他变化。然而，这些影响取决于存在的水量和类型（增塑/非增塑）。本研究的目的是确定用于确定聚合物（Eudragit RLPO）水分含量的不同方法的准确性，并确定存在的水的类型。聚合物粉末储存在不同的相对湿度（33、56、75、94%）下。使用了四种水分测定方法[干燥失重、热重分析（TGA）、差示扫描量热法（DSC）和卡尔费休滴定法（KFT）]来测定水分含量。DSC 用于研究湿样和干样的热行为。使用 Gordon-Taylor 方程计算增塑水的量。扫描电子显微镜用于检查热分析后聚合物颗粒的形态。结论是 KFT 准确地确定了总含水量，但热方法低估了总含水量。然而，KFT 没有表明存在的水的类型。Gordon-Taylor 模型表明，在含有 10%水分的聚合物中，只有约 25%的水分作为增塑剂。应使用补充方法来测量药物聚合物的水分含量。
