Quantitative analysis using ATR-FTIR Spectroscopy

Significance of the Topic

Infrared spectroscopy with ATR-FTIR accessory enables non-destructive, reagent-free analysis of diverse samples, facilitating rapid and accurate quantification in quality control, research, and industrial settings.

Objectives and Study Overview

This study demonstrates the quantitative performance of Agilent Cary 600-series FTIR spectrometers combined with a PIKE MIRacle single bounce diamond ATR, using ethanol-in-water as a model system. Key goals include evaluating calibration accuracy and determining the limit of detection (LOD) for ethanol in aqueous solutions.

Methodology

• Calibration Preparation: Ethanol standards (1.0–5.0 % v/v) were prepared by serial dilution in deionized water.
• Spectral Acquisition: Spectra were recorded against a water background, using 16 sample scans and 64 background scans at 4 cm⁻¹ resolution with BH4 apodization and zero filling factor of 2.
• Data Processing: Peak area at the C–O stretch (1045 cm⁻¹) was integrated and baseline-adjusted interactively in Resolutions Pro software to build calibration curves.

Used Instrumentation

• FTIR Spectrometers: Agilent Cary 660 (mechanical-bearing) and Cary 670 (air-bearing) FTIR.
• ATR Accessory: PIKE MIRacle single bounce diamond crystal.
• Software: Resolutions Pro with Quant Calibration and Noise applications.

Results and Discussion

• Calibration Linearity: Excellent correlation across 1.0–5.0 % v/v EtOH/H₂O with interactive inclusion/exclusion of data points for robust model refinement.
• Accuracy: A 0.500 % v/v sample was measured at 0.504 % v/v (accuracy better than 0.5 %).
• Limit of Detection: Defined as three times peak-to-peak noise (1220–1120 cm⁻¹), yielding LODs of 0.04 % v/v for Cary 670 and 0.08 % v/v for Cary 660. The C–O stretch at 1045 cm⁻¹ is clearly detectable even at 0.04 % v/v.
• Instrument Sensitivity: High IR throughput of Cary 600 series offsets ATR attenuation (70–90 %), reducing scan requirements and accelerating analysis.

Benefits and Practical Applications

ATR-FTIR with Agilent Cary 600-series offers rapid analysis with minimal sample preparation, high sensitivity for low-concentration analytes, and user-friendly software for quantitative modeling. Ideal for routine QA/QC, process monitoring, and research labs requiring fast turnaround.

Future Trends and Opportunities

• Automation and High-Throughput Screening: Integration with autosamplers and robotic platforms for increased throughput.
• Advanced ATR Materials: Development of novel IRE crystals to extend spectral range and chemical resistance.
• Enhanced Software Analytics: Implementation of chemometric algorithms and AI-driven calibration for complex mixtures.
• In-Situ and On-Line Monitoring: Real-time process control using flow-through ATR cells.

Conclusion

The combination of PIKE MIRacle ATR and Agilent Cary 600-series FTIR provides a powerful platform for accurate, sensitive, and rapid quantitative infrared analysis. High energy throughput and intuitive software tools streamline calibration and detection workflows, demonstrating robust performance even at trace analyte levels.

References

1. Boyd S. and Kansiz M. Highest Available Signal-To-Noise Performance, Delivering Superior Sensitivity and Analytical Performance, Advantage Note SI-01353, Agilent Technologies, 2011.
2. Resolutions Pro Software Help Files, Agilent Technologies.
3. Harris Daniel C. Quantitative Chemical Analysis, W. H. Freeman, 2006. ISBN 071677041.