On-line UV-NIR spectroscopy as a process analytical technology (PAT) tool for on-line and real-time monitoring of the extraction process of Coptis Rhizome

An on-line ultraviolet-near infrared (UV-NIR) spectroscopy-based method for on-line and real-time monitoring of the extraction process of Coptis Rhizome was proposed. Two fiber optic probes were designed to transmit NIR radiation through a pathlength flow cell to the NIR spectrometer for collecting spectra in real-time. Partial least squares regression (PLSR) calibration model of berberine concentration was established and validated. The correlation coefficient (R) and root mean square error of calibration (RMSEC) for the calibration set were 0.9968 and 0.0253 mg mL−1, and the R and root mean square error of prediction (RMSEP) for the validation set were 0.9970 and 0.0242 mg mL−1, respectively. This proved that the calibration model had good performance. The established model was used for on-line and real-time monitoring of the extraction process of Coptis Rhizome with satisfactory results. Both the moving block of standard deviation (MBSD) and relative concentration changing rate (RCCR) methods were used to identify the end point of extraction process. The results demonstrate that the proposed method and established model can provided instant feedback of indicator concentration in the extraction process of herbal medicines.