Guide to TRS100 Analytical Method Development

Significance of Topic

This guide addresses the critical need for rapid, non-destructive content uniformity testing in pharmaceutical solid dosage forms. Transmission Raman Spectroscopy (TRS), exemplified by the Agilent TRS100, enables whole‐tablet analysis without sample preparation, offering significant reductions in analysis time, consumables, solvent waste, and operational costs while improving throughput and sustainability.

Objectives and Overview

The aim of this whitepaper is to outline a robust, data-driven workflow for developing quantitative TRS methods to regulatory standards, from feasibility through routine application. Key stages include feasibility assessment, calibration design via DoE, method validation against compendial criteria, regulatory submission strategy, and life-cycle management.

Fundamentals and Methodology

Raman spectroscopy provides molecular fingerprints via inelastic light scattering. Transmission geometry collects bulk‐through‐sample signal, contrasting with surface-biased back-scatter. TRS100 employs a 785 nm laser (≤650 mW) with adjustable spot sizes (2–8 mm) and interchangeable collection optics.

• Chemometrics: Multivariate techniques such as Partial Least Squares (PLS) and Principal Component Analysis (PCA) are essential to deconvolute overlapping spectral features and build quantitative models.
• Sample Design: A central composite or tailored DoE spanning API and excipient concentration ranges ensures robust calibration.
• Acquisition Parameters: Optimize laser power, exposure time, and accumulations to maintain signal below ~40 000 counts per acquisition. Monitor for fluorescence and photobleaching effects.
• Preprocessing: Typical workflow includes baseline correction (e.g., Whittaker), normalization (e.g., SNV or MSC), and mean centering. Latent variable selection should balance model complexity with predictive performance (avoid overfitting).
• Validation Strategy: Perform cross‐validation (RMSEC ≈ RMSECV) and test independent samples (RMSEP) across production lots, compaction forces, operators, and instruments to ensure accuracy, precision, specificity, linearity, range, and robustness per ICH Q2(R1) and USP <1225> criteria.

Used Instrumentation

The Agilent TRS100 Transmission Raman Spectrometer features:

• 785 nm diode laser, up to 650 mW, with user-selectable spot sizes (2, 4, 8 mm).
• Interchangeable collection optics (small, medium, large) for optimizing sampled volume.
• Integrated software for spectral acquisition control, chemometric preprocessing, multivariate modeling, and validation reporting.

Main Results and Discussion

Feasibility scans demonstrated clear API peak visibility in coated tablets, powders, and capsules; aqueous solutions were less favorable. Spiking studies confirmed linear spectral response to API concentration. Calibration models built on centrally designed DoE (8–25 blends) achieved R² > 0.99 and RMSEP within prespecified acceptance limits (e.g., ±3% %LC). Robustness tests including compaction force variation and excipient supplier changes yielded stable predictions and identifiable Hotelling/Q-residual patterns. Inter-instrument and inter-day precision studies showed %RSD < 3%.

Benefits and Practical Applications

Key advantages of TRS100 methods include:

• No sample destruction, solvents, or extensive sample prep.
• Rapid analysis (typically 10–60 s per tablet).
• Whole‐tablet bulk measurement ensures representative results.
• High throughput for routine quality control or PAT applications.
• Reduced regulatory submission risk by demonstrating equivalence to HPLC.

Future Trends and Potential Uses

Advancements to watch include:

• Integration of TRS in continuous manufacturing and real-time release testing (RTRT).
• Automated model maintenance and update via AI/ML algorithms.
• Expansion to complex formulations (multilayer tablets, gels, suspensions) and other dosage forms.
• Harmonization of regulatory guidance specific to TRS.

Conclusion

Transmission Raman Spectroscopy with the TRS100 instrument provides a validated, rapid, and environmentally sustainable alternative to conventional HPLC for content uniformity and assay testing. A systematic, QbD-inspired workflow covering feasibility, calibration, validation, submission, and lifecycle management enables successful regulatory approval and routine adoption.

References

• International Council for Harmonization. Q2(R1) Validation of Analytical Procedures.
• United States Pharmacopeia <1225> Validation of Compendial Procedures; <1039> Chemometrics; <858> Raman Spectroscopy.
• EMA Guideline on the Use of Near Infrared Spectroscopy for Analytical Procedures (2014).