Biodiesel in diesel fuel using the Agilent 5500t FTIR by EN14078 method

Importance of the Topic

Biodiesel blends are increasingly used to reduce greenhouse gas emissions and dependence on petroleum. Accurate, rapid quantification of fatty acid methyl esters (FAME) in diesel is essential for quality control, regulatory compliance (EN14078), and ensuring engine performance.

Objectives and Study Overview

This application note demonstrates the use of an Agilent 5500t FTIR spectrometer to determine biodiesel concentration in diesel fuel between 1% and 6% (v/v) in accordance with EN14078. Two stock solutions (20% and 4% v/v biodiesel in diesel) were prepared and serially diluted to generate calibration standards (0.8, 1.2, 3, 4, 6, 8, 10% v/v). Measurements were performed in triplicate to build and validate a calibration model.

Methodology and Instrumentation

The analytical setup included:

• FTIR Spectrometer: Agilent 5500t
• Liquid Cell: Tumbler transmission cell with 100 µm pathlength
• Resolution: 4 cm⁻¹, 32 scans per sample (15 s acquisition)
• Baseline Correction: Two-point baseline at 1820 cm⁻¹ and 1670 cm⁻¹
• Software: Agilent MicroLab for calibration and prediction

Each standard was measured three times. The absorbance peak at 1745 cm⁻¹, characteristic of the ester carbonyl group, was used for quantification.

Main Results and Discussion

The measured absorbance ranged from 0.15 Abs at 0.8% to 1.63 Abs at 10% biodiesel. A linear calibration curve of absorbance versus concentration yielded a correlation coefficient (R²) of 0.999 over 0.8–10% v/v. The MicroLab method, formatted to report %×10 for 0.1% resolution, predicted biodiesel content in validation samples with an average error of 0.13% v/v and a maximum error of 0.20% v/v.

Benefits and Practical Applications

This FTIR-based approach offers:

• Rapid analysis (15 s per sample)
• High accuracy and precision in the 1–6% v/v range required by EN14078
• Minimal sample preparation
• Ease of method deployment via MicroLab software

These features support routine QC in fuel production, blending operations, and regulatory testing laboratories.

Future Trends and Potential Uses

Advances likely include expanded spectral libraries for alternative biofuels, integration with automation platforms for high-throughput screening, and coupling with chemometric models to extend the dynamic range and detect contaminants or oxidation products. Portable FTIR instruments may enable on-site analysis at fuel terminals and distribution points.

Conclusion

The Agilent 5500t FTIR with a 100 µm liquid cell reliably quantifies biodiesel in diesel by EN14078. The method delivers fast, precise results suitable for industrial and regulatory applications, with straightforward implementation in MicroLab software.