Improving verification with Orbital Raster Scan technology

Significance of the Topic

Orbital Raster Scan technology addresses a key limitation of traditional Raman spectroscopy when analyzing samples with heterogeneous composition. By expanding the interrogation area while preserving spectral resolution, ORS ensures representative sampling of materials that vary spatially, such as pharmaceutical tablets, reducing degradation risk and sampling error.

Objectives and Overview

The study aimed to demonstrate the improvement in spectral consistency and speed of analysis achieved by ORS compared to conventional point sampling. Specific goals included:

• Comparing multiple point measurements (ORS off) with a single ORS scan on effervescent cold tablets
• Quantifying spectral variance reduction
• Applying statistical verification (p-value) to distinguish two commercial cold remedies

Methodology and Instrumentation

Instrumentation relied on the Metrohm Instant Raman Analyzer MIRA P equipped with ORS, featuring a high-speed rotating mirror to raster a focused 785 nm laser across a large sample area. Key configuration parameters:

• Excitation wavelength: 785 nm
• Laser power: 5 mW
• Attachment: Short-working-distance lens
• Software: MiraCal with USP library
• Integration times: 1 s to 10 s

Effervescent cold relief tablets were sampled immediately after removal from packaging. For ORS off experiments, 60 spectra from varied tablet locations were acquired to build an averaged reference. A single ORS-enabled scan was then recorded. Finally, Alka-Seltzer Plus samples underwent ORS scanning and statistical comparison against the Equate training set.

Main Results and Discussion

Overlaying 60 ORS-off spectra revealed significant variability across heterogeneous tablet surfaces. Averaging these measurements produced improved consistency, but still required substantial acquisition time. In contrast, a single ORS scan yielded a spatially averaged spectrum equivalent to the multi-point average and reduced sampling effort.

Statistical verification using p-values demonstrated clear differentiation between Equate and Alka-Seltzer tablets. A single ORS scan of the competitor product resulted in a p-value of 0.008, indicating a failed match despite visual spectral similarity.

Benefits and Practical Applications

• Rapid acquisition of representative spectra with one measurement
• Improved reliability for QA/QC of heterogeneous materials
• Reduced risk of laser-induced sample damage
• Field-deployable analysis with handheld Raman devices

Future Trends and Opportunities

Advances may include integrating ORS with automated sample mapping, combining data analytics and machine learning for real-time spectral interpretation, and extending applications to pharmaceuticals, forensic analysis, materials research, and environmental monitoring. Enhanced miniaturization and software connectivity will further broaden the use of ORS-enabled Raman in diverse industrial settings.

Conclusion

Orbital Raster Scan technology in the MIRA P Raman analyzer delivers accurate, representative spectra from heterogeneous samples in a fraction of the time required by traditional methods. It streamlines chemical identification and verification workflows, offering robust performance for both laboratory and field applications.

Reference

• Metrohm AG Improving verification with Orbital Raster Scan technology Application Note AN-RS-011