Ultrafiltration–Diafiltration Inline Monitoring for Protein and Excipient Concentration: A Comparison of Mid-Infrared, Raman, and Variable Pathlength Ultraviolet Spectroscopy

In biopharmaceutical production, ultrafiltration and diafiltration (UF/DF) becomes essential when high concentrations and tight control over the final formulation of drug substance is needed. Currently, the possibilities for direct inline monitoring of this process step are limited. This study evaluates the effectiveness of three spectroscopic techniques, i.e., mid-infrared (MIR), Raman, and variable pathlength ultraviolet (UV), or inline monitoring of protein concentration. Results demonstrate that all three techniques are suitable for monitoring this operation, with root mean squared errors of prediction (RMSEP) of 5.0, 3.2, and 3.2% for MIR, variable pathlength UV, and Raman spectroscopy, respectively. MIR and Raman spectroscopy were also tested for the quantification of excipient concentration in solution, with promising results. These findings indicate that all these advanced spectroscopic methods can enable inline monitoring capabilities, thus reducing the reliance on time-consuming offline analytics and leading to shorter development timelines. This integration of process analytical technology (PAT) tools in biopharmaceutical manufacturing can offer potential improvements in process control and variability reduction.