Orbital Raster Scan (ORS™)

Importance of the topic

Raman spectroscopic analysis faces trade-offs between spatial resolution and signal sensitivity when probing heterogeneous samples. Orbital Raster Scanning (ORS) addresses these challenges by rapidly moving a tightly focused 785 nm laser beam in a circular path to interrogate a larger sample area without sacrificing spectral quality or risking localized overheating.

Objectives and study overview

This application note demonstrates how ORS enhances representative sampling, preserves delicate materials, and improves data consistency across diverse use cases. Three illustrative cases are examined: pharmaceutical quality control, non-destructive polymer identification, and reproducible analysis of SERS substrates.

Methodology and instrumentation

ORS engages a focused 785 nm laser scanned along a 2000 µm diameter orbit to average signals over heterogeneous surfaces.
Key instruments equipped with ORS include:

• MIRA P Advanced – handheld 785 nm Raman analyzer, FDA 21 CFR Part 11 compliant, multiple sampling attachments.
• MIRA DS Advanced XL – rugged 785 nm handheld Raman for illicit material detection, advanced spectral libraries, universal attachments.
• MISA Advanced – portable 785 nm SERS analyzer, optimized for trace detection via nanoparticle-embedded P-SERS substrates.

Low laser powers (≈50 mW) at 785 nm suffice for high-quality spectra, avoiding the higher powers required at 1064 nm.

Main results and discussion

1. Representative pharmaceutical sampling
ORS is endorsed by the European Pharmacopoeia (Ph. Eur. 2.2.48) to ensure measurement representativeness in tablets, overcoming the limitations of small beam diameters relative to particle sizes.

2. Sample preservation in polymer analysis

• Fixed-beam 1064 nm tests on a plastic pen barrel caused burning at high power and failed to identify the material.
• MIRA XTR DS with ORS acquired undamaged, high-quality spectra at low power and correctly identified polystyrene and polyphenylene ether (PPE) with a Hit Quality Index of 0.91.

3. Consistent SERS measurements on P-SERS substrates

• SEM images reveal heterogeneous nanoparticle distribution on paper-based P-SERS strips.
• Comparing SERS of BPE with ORS off versus on shows ORS reduces signal variability from 10% to 1.4%, ensuring reproducible trace analysis.

Benefits and practical applications

• Enhanced representativeness through area averaging.
• Minimized risk of sample damage by distributing laser energy.
• Improved reproducibility and analytical confidence.
• High spectral resolution combined with sufficient sensitivity.

Future trends and opportunities

ORS may integrate with automated sampling, hyperspectral imaging, and machine learning for real-time analysis. Expanding its use in regulated environments, in-line process monitoring, and novel material characterization promises broader impact in research and industry.

Conclusion

Orbital Raster Scanning elegantly balances resolution, sensitivity, and sample integrity. By rastering a low-power 785 nm beam, ORS delivers representative, high-quality spectra across applications, enhancing the reliability of Raman and SERS analyses.

References

1. European Pharmacopoeia 10th Edition. European Directorate for the Quality of Medicines and Healthcare (EDQM).
2. Smith CJ, Stephens JD, Hancock BC, Vahdat AS, Cetinkaya C. Acoustic Assessment of Mean Grain Size in Pharmaceutical Compacts. Int. J. Pharm. 2011;419(1-2):137–146.
3. Yu WW, White IM. Inkjet Printed Surface Enhanced Raman Spectroscopy Array on Cellulose Paper. Anal. Chem. 2010;82(23):9626–9630.