See Through Raman Technology: Expanded capabilities for through package identification using 785 nm and 1064 nm excitation Raman

Importance of the topic

Raman spectroscopy is a powerful non-destructive analytical method widely employed for rapid molecular identification in fields ranging from pharmaceuticals to law enforcement. Traditional Raman requires direct access or transparent containers, limiting its utility in field applications where opening packages is impractical. See-through Raman (STRaman™) technology overcomes these limitations by enabling identification through diffusely scattering and opaque packaging, improving safety, speed, and sample integrity in quality control, customs inspection, and first-responder scenarios.

Objectives and study overview

The primary objectives of the study were to:

• Demonstrate STRaman performance using both 785 nm and 1064 nm laser excitation.
• Evaluate identification capabilities through a variety of nontransparent packaging materials (plastic bottles, envelopes, paper sacks).
• Assess the impact of sampling depth and laser power density on sample integrity and identification accuracy.

Methodology

STRaman technology employs a large-area sampling optic and advanced algorithms to enhance signal contributions from underlying materials while suppressing packaging fluorescence and Raman background. Compared with confocal Raman, this non-focused approach reduces power density at the sample surface, preventing burning and yielding reproducible spectra from heterogeneous matrices. Identification relies on scaled subtraction of packaging signals and library searching using a hit quality index (HQI) threshold.

Used Instrumentation

• STRam®-785 (BWT-840000676): Portable Raman spectrometer with 785 nm excitation, high-throughput spectrometer, specialized sampling optics and STRaman™ algorithms for plastic bottles, envelopes, tablet coatings.
• STRam®-1064 (BWT-840000945): Transportable system with 1064 nm excitation for reduced fluorescence interference, enabling through-package identification in dark colored and multi-layer kraft paper sacks, fiber bags, and tape-sealed containers.

Main results and discussion

Identification through white polyethylene bottles successfully recovered sodium benzoate spectra via scaled subtraction, matching reference spectra. High laser power at reduced density allowed safe measurement of dark powders without burning. Through multi-layer kraft paper sacks, including white and brown paper combinations with plastic lining, STRaman-1064 achieved positive identification of excipients such as calcium carbonate, lactose, and even weak Raman scatterers like trisodium phosphate (HQI > 85, margin > 2), whereas 785 nm excitation failed under high fluorescence.

Practical benefits and applications

• Non-invasive material verification without opening packages or direct contact.
• Preservation of sample integrity and containment, essential for hazardous or controlled substances.
• Rapid incoming goods inspection in pharmaceutical manufacturing, customs screening, and forensic on-site analysis.
• Improved reproducibility for heterogeneous samples due to larger sampling area.

Future trends and potential applications

Developments may include integration of artificial intelligence for automated spectral deconvolution, expansion to near-infrared and UV excitation sources, miniaturized handheld units for point-of-care diagnostics, and coupling with imaging modalities for spatially resolved through-package analysis. Integration into automated conveyor-based systems could enable continuous quality monitoring in manufacturing lines.

Conclusion

See-through Raman technology significantly extends the applicability of Raman spectroscopy to samples within opaque and diffusely scattering containers. By leveraging larger sampling areas, optimized excitation wavelengths, and advanced algorithms, STRaman allows non-destructive, rapid, and reliable material identification across diverse packaging types, opening new opportunities for in-field and industrial analytical workflows.

References

1. J. Zhao, K. A. Bakeev, J. Zhou. Raman Spectroscopy Peers Through Packaging. Photonics Spectra, February 2018.
2. K. A. Bakeev. See-Through Science. The Analytical Scientist, May 2018.