The chromatographic elution process is a key step in the production of notoginseng total saponins. Due to quality variability of loading samples and resin capacity decreasing over cycle time, saponins, especially the five main saponins of notoginseng total saponins, need to be monitored in real time during the elution process. In this study, convolutional neural networks, one of the most popular deep learning methods, were used to develop quantitative calibration models based on in-line near-infrared spectroscopy for notoginsenoside R 1 , ginsenosides Rg 1 , Re, Rb 1 and Rd, and their sum concentration, with root mean square error of prediction values of 0.87, 2.76, 0.60, 1.57, 0.28, and 4.99 mg/mL, respectively. Partial least squares calibration models were also developed for model performance comparison. Results show predicted concentration profiles outputted by both the convolutional neural network models and partial least squares models show agreements with the real trends defined by reference measurements, and can be used for elution process monitoring and endpoint determination. To the best of our knowledge, this is the first reported case study of combining convolutional neural networks and in-line near-infrared spectroscopy for monitoring of the chromatographic elution process in commercial production of botanical drug products.
K E Y W O R D Sbotanical drugs, chromatographic elution process, convolutional neural network, deep learning, nearinfrared spectroscopy Article Related Abbreviations: BN, batch normalization; CNN, convolutional neural network; FC, fully connected; NIR, near-infrared; NTS, notoginseng total saponins; PLS, partial least squares; ReLU, rectified linear unit; RMSEP, root mean square error of prediction.[1-3] and a dietary supplement in USA [4]. Notoginseng total saponins (NTS) are the main active ingredients of Sanqi and have pharmacological activities such as anti-atherosclerotic, haemostatic, neuroprotective, anti-inflammatory, antiaging, and antioxidant effects [1,2]. Notoginsenoside R 1 , ginsenosides Rg 1 , Re, Rb 1 , and Rd are the five main saponins of NTS. These five saponins are chosen as index components for quality evaluation of NTS [5] and have been taken as qualitymarkers (Q-markers) of NTS [6].As a key step in the production of NTS, the column chromatographic process is used for removing impurities and