Accessories for Fourier Transform Infrared Spectrophotometers and Raman Spectrophotometer

Importance of Accessory Selection in FTIR and Raman Spectroscopy

Fourier Transform Infrared (FTIR) and Raman spectroscopies are foundational analytical techniques in chemistry, material science and quality control. The performance and versatility of these methods depend critically on the choice of accessories—prisms, cells, reflectance attachments, detectors and automated sampling modules—that adapt the spectrometer for different sample states (solids, liquids, gases), thicknesses and measurement modes. Thoughtful accessory selection enhances sensitivity, expands measurable wavelength ranges (from far-IR to near-IR), permits non-destructive and micro-focal analysis, and supports high-throughput automation.

Objectives and Article Overview

This application note provides a structured guide for selecting FTIR and Raman spectrophotometer attachments, including:

• An introduction to FTIR and Raman principles.
• A flowchart for matching accessory types to sample forms and analytical objectives.
• A comprehensive catalogue of Shimadzu accessories for FTIR series, infrared/Raman microscopes and NIR measurements.
• An overview of accessory features, measurement capabilities and instrument compatibility.

Methodologies and Instrumentation

1. FTIR Fundamentals
• FTIR records the intensity of IR light transmitted, reflected or absorbed by a sample irradiated with infrared beams. Its advantages over dispersive IR include multiplex measurement, high throughput and superior wavenumber accuracy.
• Sample form (liquid, solid, film, powder, gas) determines the analysis mode and accessory selection.

2. Raman Fundamentals
• Raman measures laser-excited scattered light to detect vibrational modes (e.g., C–C, S–S) not observed by FTIR. A focused laser enables three-dimensional positioning and spot sizes down to a few micrometers.

3. Accessory Types
• ATR (Attenuated Total Reflectance): Single-reflection (diamond, Ge, ZnSe prisms), multi-reflection, horizontal and integral cell attachments. No sample grinding, ideal for surfaces, films, rubbers and liquids.
• Specular Reflectance & Reflection Absorption: SRM and RAS attachments convert reflection spectra on metal substrates into absorption spectra via Kramers-Kronig, for thin films and molecular orientation studies.
• Diffuse Reflectance: DRS modules and SiC samplers for powder analysis and HPLC fraction measurements. Kubelka-Munk conversion yields concentration-proportional data.
• FTIR Microscopy: AIMsight IR and AIRsight IR/Raman microscopes with video-assisted positioning, automatic contaminant recognition, T2SL or TEC MCT detectors, ATR objectives and particle analysis software.
• Raman Microscopy: Confocal optics, selectable objective lenses (50×, 100×), ND filters for fluorescence control and sub-5 µm spatial resolution.
• Transmission Cells: Demountable, sealed liquid and fixed thickness cells (NaCl, KBr, KRS-5 windows); diamond compression cells for microfibers and small samples.
• Gas Cells: Short-path (5, 10 cm) and long-path multiple-reflection cells for trace gas quantitation; NaCl, KBr, KRS-5, CaF2 windows.
• Near-Infrared (NIR): InGaAs detector kits for IRTracer-100/IRPrestige-21; diffuse reflectance (UpIR A) and integrating sphere (IntegratIR A) for powders, liquids, pellets and fibers.
• Automation & Purge Systems: Sample switchers, ASC for transmission and diffuse reflectance, purge control kits, dry air generators and CO2 scrubbers.
• Detectors: Optional T2SL (liquid nitrogen-cooled), room-temperature DLATGS, external optical switching for microscopy.
• Cell Window Materials: KBr, NaCl, KRS-5, ZnSe, sapphire, diamond, and their spectral ranges, refractive indices and chemical compatibilities.

Main Results and Discussion

The accessory line-up supports a wide array of analytical challenges:

• Surface and Film Analysis: ATR and specular/absorption reflectance attachments enable non-destructive surface-layer spectra without slicing thin films or coatings.
• Powder and Trace Solids: Diffuse reflectance and SiC samplers simplify quantitative pellet-free measurements; IR microscopy resolves features down to 1 µm and particle analysis quantifies microplastic contamination.
• Liquid and HPLC Fractions: Sealed transmission and ATR cells, combined with automated samplers, facilitate high-sensitivity quantitation of volatile and non-volatile components.
• Gas Monitoring: Long-path gas cells and automated flow systems achieve ppm-level detection for environmental and process gas analysis.
• NIR Quality Control: Rapid, non-invasive compositional analysis of raw materials and formulations via reflectance and integrating sphere accessories.
• Microscale Imaging: Coupled IR/Raman microscopy delivers chemical maps, spectral overlays and statistical particle metrics for failure analysis, biomedical and materials research.
• High-Throughput & Kinetics: Automated sample changers, rapid scan and time course software allow dynamic reaction monitoring and large batch screening.

Benefits and Practical Applications

• Enhanced Workflow Efficiency: Plug-and-play accessories with automatic recognition minimize setup time.
• Expanded Analytical Range: Extend the measurable spectrum from far-IR to NIR, accommodate diverse sample types and maximize sensitivity.
• Micro-Analysis Capability: ATR objectives, confocal Raman, and IR microscopy resolve sub-10 µm features.
• Quantitative Accuracy: Depth-correction software for ATR, Kubelka-Munk for diffuse reflectance and PLS chemometric tools ensure reliable quantitation.
• Non-Destructive Testing: ATR and reflection modes preserve samples for further analyses.
• Regulatory Compliance: Dedicated pharma reporting, spectrum validation kits, and traceable protocols support quality assurance in pharmaceutical and food industries.

Future Trends and Potential Applications

• Integration with AI: Leveraging advanced spectral libraries, machine learning for automated identification and anomaly detection.
• Lab-on-Fiber: Development of fiber-optic ATR probes for in situ process and environmental monitoring.
• Correlative Microscopy: Coupling FTIR/Raman with SEM/EDS for comprehensive chemical and morphological characterization.
• High-Throughput Screening: Robotics and micro-well arrays for combinatorial materials discovery.
• Advanced Chemometrics: Real-time PLS and multivariate curve resolution for complex matrix analysis.

Conclusion

The strategic selection of FTIR and Raman accessories transforms standard spectrometers into versatile platforms capable of addressing a broad spectrum of analytical challenges. From ATR surface analysis and diffuse reflectance of powders to IR/Raman microscopy and automated NIR quantitation, the right combination of cells, prisms, detectors and software ensures optimal sensitivity, spectral fidelity and productivity. Continuous innovation in accessory design and integration with automation and advanced data processing will further broaden the scope of vibrational spectroscopy in research and industry.

References

No specific literature references were provided in the source document.