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 widely used non-destructive analytical technique that provides specific molecular information. Its field applications, including chemical identification for security, pharmaceuticals and materials control, have been limited by the inability to probe samples through opaque packaging. The development of see through Raman technology addresses this barrier, enabling rapid, contactless analysis of substances inside containers without compromising integrity.

Objectives and Study Overview

This work introduces Metrohm AGs patented see through Raman approach applied to handheld systems at 785 nm and 1064 nm excitation. Goals include extending sampling depth beneath diffusely scattering layers, reducing power density to avoid sample damage, and integrating advanced algorithms to separate packaging and sample signals for accurate identification.

Methodology and Instrumentation

The see through Raman design employs specialized sampling optics with a larger illumination and collection area compared to confocal setups. This geometry enhances signal contributions from deeper material layers while lowering the laser power density at the surface. Advanced chemometric algorithms subtract or filter out the packaging Raman and fluorescence background to isolate the analyte signature. The technology is implemented in two portable systems:

• STRam 785 nm (product code BWT-840000676) combining a high throughput spectrometer with see through sampling optics and identification software
• STRam 1064 nm (product code BWT-840000945) optimized for reduced fluorescence in dark or colored packaging

Main Results and Discussion

Demonstrations with the 785 nm STRam include successful identification of sodium benzoate through a white polyethylene bottle, confirmed by spectral subtraction and comparison with reference spectra. The system also acquired Raman data from a black powder at full laser power without burning. With the 1064 nm STRam, various excipients including trisodium phosphate—the weakest Raman scatterer in the test—were positively identified through multi-layer kraft paper sacks. Identification criteria used a hit quality index threshold of 85 and a margin above the second best match, ensuring reliable library searches even under high fluorescence background. These results validate extended sampling depth, effective background removal, and robust performance across diverse packaging materials.

Benefits and Practical Applications

The see through Raman approach offers:

• Preservation of sample and packaging integrity by eliminating the need to open containers
• Lower risk of sample heating or burning due to reduced power density
• Rapid incoming goods inspection in warehouse, pharmaceutical, and security settings
• Improved repeatability for heterogeneous or mixed samples thanks to larger sampling area

Future Trends and Opportunities

Further developments may focus on integrating machine learning for enhanced spectral deconvolution, expanding excitation wavelengths for deeper penetration, and miniaturizing hardware for broader field deployment. Potential applications include forensic screening, counterterrorism, border control, and quality assurance across pharmaceutical, chemical and food industries.

Conclusion

See through Raman technology significantly improves the capability of handheld Raman instruments by enabling analysis through opaque packaging. The combination of larger sampling optics, lower power density, and advanced algorithms allows accurate, non-invasive material identification in real time, opening new use cases in both laboratory and field environments.

Reference

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