Fluorescence-free 785 nm material identification with MIRA XTR DS

Significance of the Topic

Fluorescence interference often hampers the sensitivity and specificity of Raman spectroscopy by reducing signal to noise ratio and obscuring characteristic vibrational peaks. Practical applications in security screening, food and pharmaceutical analysis, and industrial quality control require reliable identification of materials in complex or fluorescent matrices. The development of fluorescence suppression techniques enhances the versatility of handheld Raman instruments for field deployments.

Objectives and Overview of the Study

This study presents the MIRA XTR DS handheld Raman spectrometer, designed to overcome fluorescence interference using a patent pending Raman eXTRaction algorithm. The goals include demonstrating fluorescence free detection at 785 nanometers with low cost silicon detectors and low power lasers and validating performance across a range of materials including hazardous substances, colored plastics, food excipients, and illicit drug analogues.

Methodology and Instrumentation

Raman spectra were acquired from liquids in glass vials and solid samples using the MIRA XTR DS with SmartTips attachments and automated SmartAcquire routines. Comparative measurements at 785 and 1064 nanometer excitation were performed using the previous MIRA DS platform and a commercial handheld 1064 nanometer Raman device. The novel XTR algorithm separates time independent fluorescence from instantaneous Raman scattering to produce pure Raman signatures with flat baselines and enhanced peak resolution.

Main Results and Discussion

The XTR algorithm successfully extracted Raman spectra from highly fluorescent mixtures such as hydrocarbons and methamphetamine, revealing distinct vibrational peaks of both solvents and solutes. Analysis of fluorescent excipients like gum Arabic and microcrystalline cellulose showed superior signal to noise compared to traditional 785 and 1064 nanometer systems. Colored materials were identified without sample burning at low laser power, a limitation observed with high power 1064 nanometer excitation. The system also differentiated closely related narcotic analogues acetyl fentanyl and butyryl fentanyl by resolving unique peaks in the 600 to 800 cm-1 region.

Benefits and Practical Applications

The MIRA XTR DS delivers:

• Fluorescence free Raman spectra with adjustable low power excitation
• Compact rugged design for field use by defense, security, and first responders
• Flexible sampling through SmartTips for contact, through packaging, and standoff modes
• Reduced thermal damage with orbital raster scanning
• Comprehensive material identification using a library of over 21000 substances
• Real time decision support via HazMasterG3 software and mobile app integration

Future Trends and Applications

Advances may include integration of machine learning for automated spectral interpretation, expansion of spectral libraries with emerging synthetic threats, extension of XTR extraction to other excitation wavelengths, and miniaturization of components for extended operational lifetime and broader deployment in environmental monitoring, pharmaceutical manufacturing, and point of care analysis.

Conclusion

The MIRA XTR DS represents a significant evolution in handheld Raman spectroscopy by delivering affordable, low power, fluorescence free detection without compromising sensitivity or portability. Its versatile design and robust algorithmic processing enable confident material identification in challenging field environments.

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