How many medicinal slices should be used in an experiment of Chinese medicine extraction process?

The medicinal slice quantity for small-scale extraction experiments significantly impacts the repeatability of experimental results. A novel concept of representative mass of medicinal slices (RMMS) is presented in this work. RMMS is defined as "the minimum mass of medicinal slices required to ensure the repeatability of the extraction results with an acceptable threshold". Using the modified Fangjihuangqi decoction (MFD) as a case study, a method to determine RMMS was shown in this work. The active ingredient yields (AIYs) and dry matter yield (DMY) were used as the process indicators for the extraction of medicinal slices. AIYs and DMY of each medicinal slice in MFD were determined. The herbs with the relatively higher coefficient of variation (CV) value of AIYs and DMYs were identified, which were Stephaniae Tetrandrae Radix (Fangji) and Glycyrrhizae Radix et Rhizoma (Gancao). It was found that medicinal slice weights, AIYs, and DMYs followed a 3-parameter Weibull distribution. A comparison between the Monte Carlo simulation and the central limit theorem method showed that the latter method is simpler and more accurate in RMMS determination. To facilitate the use of this method by other researchers, an Excel spreadsheet for calculating RMMS is provided. We also suggest to use at least 50 pieces of medicinal slices when determining RMMS. A universal method for determining the appropriate medicinal material quantity in Chinese medicine extraction was provided, which is beneficial for improving the accuracy of research results in the development of Chinese medicine processes.