A NIR-Based Study of Desorption Kinetics during Continuous Spin Freeze-Drying

Abstract

The pharmaceutical industry is progressing toward the development of more continuous manufacturing techniques. At the same time, the industry is striving toward more process understanding and improved process control, which requires the implementation of process analytical technology tools (PAT). For the purpose of drying biopharmaceuticals, a continuous spin freeze-drying technology for unit doses was developed, which is based on creating thin layers of product by spinning the solution during the freezing step. Drying is performed under vacuum using infrared heaters to provide energy for the sublimation process. This approach reduces drying times by more than 90% compared to conventional batch freeze-drying. In this work, a new methodology is presented using near-infrared (NIR) spectroscopy to study the desorption kinetics during the secondary drying step of the continuous spin freeze-drying process. An inline PLS-based NIR calibration model to predict the residual moisture content of a standard formulation (i.e., 10% sucrose) was constructed and validated. This model was then used to evaluate the effect of different process parameters on the desorption rate. Product temperature, which was controlled by a PID feedback mechanism of the IR heaters, had the highest positive impact on the drying rate during secondary drying. Using a higher cooling rate during spin freezing was found to significantly increase the desorption rate as well. A higher filling volume had a smaller negative effect on the drying rate while the chamber pressure during drying was found to have no significant effect in the range between 10 and 30 Pa.

Highly Active Electrospinning Electrode Based on MOF for High-Performance Vanadium Flow Batteries

“…Electrospinning is characterized by low cost, flexible design and the ability to control fiber diameter and three-dimensional mesh structure, thereby enabling the production of desired electrodes for VRFBs based on specific requirements. 33,34 Compared to commercial carbon felt, electrospinning carbon nanofibers possess higher specific surface area and a broad range of material structure design possibilities, showing great potential in addressing the performance bottleneck of VRFBs electrodes. 35 However, traditional electrospinning carbon nanofibers used in VRFBs still suffer from poor electrochemical activity, limiting the application in the field of VRFBs.…”

New Trends in Freeze-Drying of Pharmaceutical Products

“…Always in the field of primary drying, Emteborg et al [ 6 ] used an infrared (IR) thermocamera, placed outside the dryer chamber, to monitor product temperature in a non-invasive way, both at the top surface and vertically, by using custom-made cuvettes, with a Ge window placed close to an IR mirror having a 45° angle. Leys et al [ 7 ] focused on the secondary drying stage, using near-infrared (NIR) spectroscopy, coupled with a PLS-based model, to track the residual moisture of the product vs. time, thus investigating the desorption kinetics and the effect of the operating conditions on the secondary drying stage. Moreover, the researchers pointed out that in the unit used for this study, where a continuous spin freeze-drying process is carried out, using high cooling rates in the freezing stage results in a higher desorption rate, due to the formation of smaller ice crystals.…”