[Application of time domain reflectometry for determination of wate content in Xiangsha Yangwei pills]

Xiangsha Yangwei pill was selected as a model drug in this research, and time domain reflectometry (TDR) was used to determine the water content in the pill. The effects of five factors including the number of pill layers, pill packing density, atmospheric moisture, ambient temperature and the ratio of pill formula were investigated on water content. The results showed that the number of pill layers and ambient temperature had significant effects on water content of pills, while the pill packing density, atmospheric moisture and pill formula ratio had little effect on the determination of water content in pills. The reflection value was stable when 6 layers of pills were used. Under the condition of 25 ℃ and 45% relative humidity, the water content of pills ranged from 4.01% to 22.38%, showing good linear relationship between water content and reflection value, and the model equation was as follows: Y=0.279X－21.670 (R²=0.997 0). Verification experiment was used to explain the feasibility of this prediction model. The precision of the method complied with the methodology standard. It is concluded that TDR can be used in determination of water content in Xiangsha Yangwei pills. Additionally, TDR, as a new way to quickly and efficiently determine the water content, has a prospect application in the processing of traditional Chinese medicine pharmacy, especially for concentrated pill.