Inline moisture analysis in fluid bed dryers by near-infrared spectroscopy

Importance of the Topic

In pharmaceutical manufacturing, controlling moisture in fluid bed drying is essential to prevent granule fracture or particle agglomeration, ensuring consistent product quality and avoiding production stoppages.

Objectives and Study Overview

This application note aims to demonstrate inline monitoring of residual moisture in fluid bed dryers using near-infrared spectroscopy (NIRS), enabling real-time decision making and integration with process control systems.

Methodology

A calibration model correlating NIR spectra to primary laboratory moisture measurements was developed. A dedicated fluid bed “spoon” probe, equipped with an air purge to clear the sampling window, was inserted directly into the dryer. Spectra in the 1100–1650 nm range were acquired every 30 seconds to capture moisture depletion trends throughout the drying cycle.

Instrumentation Used

• NIRS XDS Process Analyzer – MicroBundle SinglePoint with microbundle fiber optics for flexible probe placement up to 35 m from the analyzer
• Micro interactance reflectance probe with purge tip designed for fluid bed dryer environments

Key Findings and Discussion

The inline NIRS approach provided continuous moisture profiles that closely matched offline reference data. Real-time trend charts enabled operators to identify the drying endpoint as moisture values approached the specified lower limit, reducing over-drying and preventing material caking. Integration with PLCs or PAT software supports closed-loop control, minimizing batch-to-batch variability and eliminating laboratory-induced delays.

Benefits and Practical Applications

• Rapid, reagent-free analysis without manual sampling
• Enhanced product quality via precise endpoint determination
• Reduced downtime and reprocessing costs
• Compatibility with existing process control systems for automated operation

Future Trends and Opportunities

Advancements in Process Analytical Technology (PAT) will drive broader adoption of inline NIRS, enhanced by machine learning for predictive moisture control. Miniaturized and robust probe designs are expected to expand applications to API content analysis, blend uniformity checks, and solvent purity assessments.

Conclusion

Inline NIRS offers a powerful, nondestructive solution for real-time moisture monitoring in fluid bed dryers, improving process efficiency and ensuring consistent product quality while reducing operational costs.

References

• AN-PAN-1050 Inline moisture analysis in fluid bed dryers by near-infrared spectroscopy
• AN-NIR-016 Near-infrared spectroscopy for monitoring a single-pot granulator
• AN-PAN-1048 Inline moisture analysis in a pilot scale granulation process by NIRS
• AB-358 Analysis of residual moisture in a lyophilized pharmaceutical product by NIRS
• TA-048 Near-infrared spectroscopy for pharmaceutical analysis