Rapid Discrimination and Classification of Polymorphs Using the Agilent 8700 Laser Direct Infrared (LDIR) Chemical Imaging System

Significance of the Topic

Polymorphism in active pharmaceutical ingredients (APIs) leads to variations in solubility, stability, and bioavailability, directly impacting drug efficacy and quality control. Rapid and accurate identification of polymorphs supports consistent drug performance and regulatory compliance.

Objectives and Study Overview

This study demonstrates the use of the Agilent 8700 Laser Direct Infrared (LDIR) Chemical Imaging System for fast discrimination and spatial mapping of carbamazepine polymorphs in solid dosage forms. Key goals include:

• Establishing rapid classification methods for polymorphs and excipients
• Visualizing polymorphic conversion in real time
• Quantifying relative amounts of crystal forms

Methodology and Instrumentation

The approach integrates infrared chemical imaging with advanced software analysis:

• Instrument: Agilent 8700 LDIR System with Clarity software
• Imaging mode: Reflectance scanning at 10 µm pixel resolution (ATR down to 0.1 µm possible)
• Data acquisition: Selection of diagnostic wavelengths based on library spectra of carbamazepine forms I and III and cellulose excipient
• Method development: Automatic wavelength selection to generate rapid imaging protocols

Main Results and Discussion

Analysis of 13 mm tablets achieved full-sample classification in 27 minutes, reliably distinguishing polymorphic forms:

• Form I and III distributions mapped with high spatial resolution
• Measured surface concentrations matched known composition by weight
• Software enabled both qualitative maps and relative quantification without separate calibration methods

Benefits and Practical Applications

The Agilent 8700 LDIR system offers:

• Fast turnaround for polymorph identification and mapping
• High-resolution imaging for crystal growth monitoring
• Real-time visualization of polymorphic transitions
• Relative quantitation of polymorphs and excipients directly from imaging data

Future Trends and Opportunities

Advancements in chemical imaging will likely include:

• Integration with process analytical technology (PAT) for in situ monitoring
• Enhanced automation and machine learning–driven classification
• Miniaturized imaging probes for tablets and powders
• Expanded spectral libraries for broader pharmaceutical applications

Conclusion

The Agilent 8700 LDIR Chemical Imaging System provides a robust platform for rapid discrimination, mapping, and relative quantification of pharmaceutical polymorphs, enhancing quality control and formulation development workflows.

Reference

1. Czernicki W; Baranska M. Carbamazepine polymorphs: Theoretical and experimental vibrational spectroscopy studies. Vibrational Spectroscopy. 2013, 65:12–23.
2. Grzesiak AL; Lang M; Kim K; Matzger AJ. Comparison of the four anhydrous polymorphs of carbamazepine and the crystal structure of form I. J. Pharm. Sci. 2003, 92:2260–2271.