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

Significance of the topic

Raman spectroscopy is widely valued for rapid, non-destructive molecular identification in pharmaceuticals, materials science, forensics and field applications. Conventional Raman requires direct access or transparent containers, limiting its utility for packaged goods. See-Through Raman (STRaman) extends analysis to diffusely scattering and opaque barriers, enabling non-invasive inspection through plastic bottles, paper sacks, envelopes and coatings. This advance streamlines incoming goods control, supports first-responders and maintains sample integrity without opening packages.

Objectives and study overview

This work introduces and evaluates Metrohm’s STRam handheld Raman systems with 785 nm and 1064 nm excitation. Key goals include:

• Demonstrating measurement through opaque packaging layers.
• Comparing performance at 785 nm and 1064 nm for fluorescent and dark materials.
• Validating identification algorithms that isolate sample spectra from barrier contributions.

Methodology and Instrumentation

The STRam systems integrate a high-throughput spectrometer, custom sampling optics and advanced signal-processing algorithms. Key features include a large, low-power density sampling area and increased depth penetration. Two configurations are used:

• STRam-785: Handheld Raman with 785 nm excitation optimized for general materials and lightly colored packaging.
• STRam-1064: Portable Raman with 1064 nm laser to minimize fluorescence when probing dark or multi-layer paper and plastic barriers.

Both instruments record diffusely scattered Raman photons from within the container, then apply algorithmic spectral subtraction to extract the target material signature.

Results and Discussion

Through-packaging identification was achieved for a variety of sample/barrier combinations:

• White polyethylene bottles: Sodium benzoate spectra obtained through bottle walls with STRam-785, isolating sample features by subtracting bottle contributions.
• Coated tablets and black powders: Colored and dark samples measured at full power without thermal damage due to the reduced power density of the larger probe spot.
• Kraft paper sacks: Multi-layer white and brown paper bags containing excipients (e.g., calcium carbonate, trisodium phosphate) were analyzed with STRam-1064. Even weak scatterers like trisodium phosphate yielded positive identifications (HQI >85, margin >2) despite strong fluorescence background.

These findings confirm that STRaman’s deeper sampling and algorithmic deconvolution reliably identify materials under challenging packaging conditions.

Benefits and Practical Applications

The STRam technology offers several practical advantages:

• Non-invasive inspection: No need to open or compromise packaging.
• Enhanced safety: Limits operator exposure to hazardous substances.
• Field deployment: Portable systems facilitate on-site QC, customs screening and emergency response.
• Improved repeatability: Larger sampling area reduces effects of sample heterogeneity.

Future Trends and Opportunities

Potential developments include:

• Miniaturization of high-throughput optics for ultra-portable devices.
• Cloud-based spectral libraries and AI-driven identification algorithms.
• Integration with complementary sensors (e.g., near-infrared, fluorescence) for multi-modal analysis.
• Expanded applications in agriculture, environmental monitoring and point-of-care diagnostics.

Conclusion

See-Through Raman technology overcomes key limitations of traditional Raman spectroscopy by enabling reliable, non-destructive identification through opaque and diffusely scattering packaging. The STRam-785 and STRam-1064 systems demonstrate robust performance across a range of materials and barriers, supporting rapid field and laboratory analyses while preserving sample and container integrity.

References

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