药物片剂中气孔体积与药片在自然状态下的总体积之比被称为孔隙率。 药物片剂在生产过程中, 由于原料的理化性质、 人为因素和环境因素的影响, 气孔的形成是不可避免的。 孔隙率是药物片剂的一个重要特性, 孔隙率的大小会影响片剂的崩解、 溶解和生物利用度。 目前常见的药片孔隙率检测手段如压汞法、 氦比重法、 红外光谱法等等, 均无法实现药片孔隙率的无损、 快速检测。 为此提出一种利用连续太赫兹波对单个药物片剂进行孔隙率检测的方法, 分别用两种标准规格的平面药物片剂作为研究对象, 使用矢量网络分析仪在500～750 GHz的频率范围内测量通过每个药片传输的信号, 从测得的S参数中提取出每个片剂的包裹相位值, 然后对包裹相位值进行相位展开和校正以得到片剂的真实相位值, 并通过计算药物片剂与空气的相位差得到药片的有效折射率。 同时使用零孔隙率近似(ZPA)的理论模型将药片有效折射率和孔隙率联系起来。 使用矢量网络分析仪测得并计算两种药片的孔隙率与采用气体置换法测量的标准孔隙率的相对误差分别为7.3%和5.3%, 实验结果表明利用连续太赫兹波检测药片孔隙率的方法具有可行性。 太赫兹波检测药片孔隙率的方法简单、 实用, 并能做到无损、 快速检测, 为今后药物片剂制造生产中的快速、 灵敏和无损孔隙率测量工作奠定基础。

The ratio of the pore volume in the drug tablet to the total volume of the tablet in the natural state is called porosity. In the production process of drug tablets, due to the physical and chemical properties of raw materials, human factors and environmental factors, the formation of pores is inevitable. Porosity is an important characteristic of drug tablets. The porosity size will affect the disintegration, dissolution and bioavailability of tablets. At present, the common methods for measuring the porosity of tablets, such as mercury intrusion method, helium specific gravity method, infrared spectroscopy, etc., can not achieve nondestructive and rapid detection of the porosity of tablets. For this reason, this paper proposes a method to detect the porosity of a single drug tablet by using continuous terahertz waves. Two standard planar drug tablets are used as research objects respectively. The signal transmitted through each tablet is measured in the frequency range of 500~750 GHz using vector network analyzer, and the packaging phase value of each tablet is extracted from the measured S parameters. Then phase unwrapping and correction are carried out to obtain the true phase value of the tablet, and the effective refractive index of the tablet is obtained by calculating the phase difference between the tablet and the air. At the same time, the theoretical model of zero porosity approximation (ZPA) is used to link tablets effective refractive index and porosity. The relative errors between the calculated porosity of the two tablets measured by the vector network analyzer and the standard porosity measured by the gas displacement method are 7.3% and 5.3% respectively. The experimental results show that measuring the tablets porosity using continuous terahertz wave is feasible. The THz wave method for measuring the porosity of tablets is simple, practical, non-destructive and fast, which lays a foundation for rapid, sensitive and non-destructive porosity measurement in the future pharmaceutical tablet manufacturing and production.