At site rock and mineral measurement using a handheld Agilent FTIR analyzer

Importance of the Topic

Rapid, in-field identification of rocks and minerals is essential for geoscientists engaged in exploration, environmental monitoring, and mining operations. Traditional FTIR methods require extensive sample preparation and laboratory conditions, which limit on-site decision making. The development of a handheld FTIR analyzer optimized for diffuse reflectance addresses these challenges by enabling molecular-level analysis directly at the sampling site.

Objectives and Study Overview

This application note evaluates the performance of the Agilent 4100 ExoScan and 4200 FlexScan handheld FTIR systems for on-site rock and mineral analysis. It describes the creation of a specialized diffuse reflectance geolibrary, compares rough versus smooth surface spectra, and demonstrates ease of use in field conditions. The goal is to illustrate how this integrated approach accelerates mineral identification with minimal sample handling.

Methodology and Instrumentation

• FTIR Analyzers: Agilent 4100 ExoScan and 4200 FlexScan, battery-powered for field portability.
• Diffuse Reflectance Interface: Enables direct collection of diffusely scattered IR light from neat rock and mineral surfaces without grinding or KBr pellet preparation.
• On-Board Geolibrary: Custom library of diffuse reflectance spectra covering igneous, metamorphic, and sedimentary materials across varied chemical classes (silicates, oxides, sulfates, phosphates, etc.).
• Spectral Acquisition: 4 cm⁻¹ resolution, 128 co-added scans, ~1 minute per measurement.

Key Findings and Discussion

The field-optimized diffuse reflectance library yields reliable matches for a broad range of geological specimens. Inclusion of both rough porous surfaces and polished crystal faces enhances matching accuracy, compensating for specular reflection components. The handheld systems consistently identify major mineral classes within minutes, and users can augment the library with custom reference spectra to address site-specific requirements.

Benefits and Practical Applications

• Rapid Decision Making: On-site molecular composition data support real-time exploration and resource assessment.
• Minimal Sample Preparation: Eliminates grinding, mixing, or pellet pressing, reducing contamination risk.
• User-Customizable Libraries: Field teams can build targeted spectral collections for unique local geology.
• Complement to Elemental Analysis: Provides vibrational fingerprinting to supplement XRF and other elemental methods.

Future Trends and Opportunities

Advances in miniaturized detectors and improved algorithms will further enhance handheld FTIR sensitivity and library coverage. Integration with GIS and cloud-based spectral sharing platforms could enable collaborative database expansion. Machine-learning approaches hold promise for automated phase quantification and detection of subtle mineralogical variations in heterogeneous samples.

Conclusion

The Agilent 4100 ExoScan and 4200 FlexScan handheld FTIR analyzers, paired with a dedicated diffuse reflectance geolibrary, provide a powerful solution for immediate, non-destructive rock and mineral identification in the field. This approach streamlines workflows, reduces reliance on laboratory infrastructure, and supports rapid geoscientific decision making.

Reference

Agilent Technologies. At-site rock and mineral measurement using a handheld Agilent FTIR analyzer: Application Note. Publication Number 5990-7794EN, 2011 (updated May 2015).