Laboratory of Polymer Chemistry and Technology, Chemistry Department, Aristotle University of Thessaloniki, 541 24 Thessaloniki, Greece.
Int J Pharm. 2012 Nov 15;438(1-2):33-44. doi: 10.1016/j.ijpharm.2012.08.056. Epub 2012 Sep 5.
Tablet coating thicknesses were estimated using several techniques such as weight gain and scanning electron microscopy (SEM), in comparison with acoustic microscopy and diffuse reflectance spectroscopy. Acoustic microscopy, used for the first time in such an application, is based on the physical phenomenon of ultrasound propagation through the materials and the echoes generated by their interfaces. Based on the time of flights (TOFs) of the echoes from the coating surface and the tablet, it is possible to calculate the coating thickness. In order to evaluate the accuracy and robustness of these methods, drug tablets were coated with Kollicoat SR polymer for several times, so that to prepare tablets with different coating thicknesses. Tablets with 3, 6 and 9 wt% coating material have been prepared and based on SEM micrographs it was found that the tablet coating thickness is 71.99 ± 1.2 μm, 92.5 ± 1.7 μm and 132.3 ± 2.1 μm, respectively (SEM analysis). The tablet coating thicknesses measured with acoustic microscopy and infrared diffuse reflectance spectroscopy, were in agreement with those obtained using SEM. This verifies that both techniques can be successfully applied for real time and non-destructive thickness measurements of tablet coating. Furthermore, both techniques, compared with SEM and weight gained measurements, are fast and fully automated.
采用增重法和扫描电子显微镜（SEM）等多种技术来估算片剂包衣厚度，同时与声显微镜和漫反射光谱法进行比较。声显微镜首次应用于此类应用中，它基于超声在材料中传播的物理现象以及其界面产生的回波。基于来自涂层表面和片剂的回波的飞行时间（TOF），可以计算涂层厚度。为了评估这些方法的准确性和稳健性，用 Kollicoat SR 聚合物对药物片剂进行了多次包衣，从而制备了具有不同包衣厚度的片剂。制备了涂层材料为 3wt%、6wt%和 9wt%的片剂，并且根据 SEM 显微照片发现片剂包衣厚度分别为 71.99±1.2μm、92.5±1.7μm 和 132.3±2.1μm（SEM 分析）。使用声显微镜和红外漫反射光谱法测量的片剂包衣厚度与使用 SEM 获得的厚度一致。这验证了这两种技术都可以成功地应用于片剂包衣的实时和无损厚度测量。此外，与 SEM 和增重测量相比，这两种技术都快速且完全自动化。
