Dynamic Vapor Sorption (DVS) in API Hygroscopicity Testing: A Practical Insight

In pharmaceutical development, API hygroscopicity—how active ingredients absorb moisture—is a key factor influencing stability, manufacturability, and shelf life. Excess moisture can trigger chemical degradation, polymorphic changes, or formulation instability. Dynamic Vapor Sorption (DVS) is a cutting-edge method used to accurately analyze moisture sorption behavior in real time.

What Is Dynamic Vapor Sorption (DVS)?

DVS is a gravimetric technique that measures how much water vapor an API sample absorbs or desorbs as relative humidity (RH) changes. It provides continuous, real-time data as RH typically cycles from 0% to 90% at constant temperature—offering a more detailed picture than traditional static methods.

Why Measure API Hygroscopicity?

• Stability Control: Moisture uptake can lead to hydrolysis, degradation, or unwanted polymorphs.

• Formulation Impact: Moisture-sensitive APIs may alter excipient compatibility or dissolution profiles.

• Manufacturing Efficiency: Knowing hygroscopic behavior helps in optimizing drying, handling, and storage conditions.

Advantages of DVS Testing

• ✅ High sensitivity: Detects small mass changes with high accuracy

• ✅ Real-time results: Tracks both absorption and desorption kinetics

• ✅ Small sample size: Requires only a few milligrams—ideal for early R&D

• ✅ Comprehensive data: Generates sorption isotherms and moisture-related thresholds

How DVS Works: A Simple Workflow

1. Prepare the API: Dry and condition the sample

2. Program RH profile: e.g., increase RH from 0% to 90% in steps

3. Monitor Mass: Continuously record sample weight changes

4. Analyze Results: Generate isotherms, determine critical RH points, model behavior

Case Example: Moisture Sorption in a Model API

• Moisture Uptake Started: At 40% RH

• Significant Mass Gain: Between 60%–80% RH

• Slow Desorption: Indicated strong water binding, suggesting need for dry storage

Conclusion

Dynamic Vapor Sorption (DVS) is a powerful tool for assessing API moisture behavior. It supports formulation design, risk assessment, and quality-by-design (QbD) initiatives by providing fast, accurate, and actionable data. For pharmaceutical companies aiming to improve product stability and compliance, integrating DVS early in the development process is a smart move.