Low level detection of biodiesel in diesel fuel using the Agilent 5500t FTIR spectrometer

Importance of the Topic

Low-level detection of biodiesel in petroleum diesel is increasingly important due to regulatory requirements and operational challenges in storage and engine performance. Small amounts of biodiesel can accelerate oxidation, promote microbial growth, and lead to compatibility issues in engines designed for pure diesel. Accurate, sensitive monitoring ensures compliance and prevents long-term storage problems.

Objectives and Study Overview

This study adapts the EN 14078 FTIR method on the Agilent 5500t spectrometer to achieve quantitative detection of biodiesel in diesel at concentrations as low as 0.025% by volume. The method was calibrated, validated up to 5% biodiesel, and designed for rapid, user-friendly operation.

Methodology

Standards were prepared by diluting biodiesel into diesel from 0% to 1.5% (v/v). Spectra were collected on two separate Agilent 5500t FTIR instruments using a 100 µm path length transmission cell. Each sample was scanned 32 times at 4 cm⁻¹ resolution, yielding a 15-second analysis per measurement. The EN 14078 specification uses the carbonyl band at 1745 cm⁻¹; this method employs peak area rather than height to lower the detection limit. Calibration was based on the integrated area of that band, producing a linear fit (R² = 0.9998). The method was implemented in MicroLab software for routine analysis.

Used Instrumentation

• Agilent 5500t FTIR spectrometer
• 100 µm path length Tumbler transmission cell
• MicroLab data acquisition and processing software

Main Results and Discussion

The modified method clearly resolved a 0.025% biodiesel signal above the diesel blank. Calibration remained linear through 1.5% and extended reliably to 5% biodiesel. A validation set spanning 0–5% returned an average relative error of 1% and a maximum error of 2%. Results demonstrate that the approach delivers precise quantitation across a broad concentration range with minimal analysis time.

Benefits and Practical Applications

• High sensitivity to detect trace biodiesel levels down to 0.025%
  
• Fast throughput: approximately 15 seconds per sample
  
• Pre-programmed method on the Agilent 5500t for ease of use
  
• Suitable for quality control, regulatory compliance, and storage monitoring in fuel depots and industrial settings

Future Trends and Potential Uses

Integration of chemometric models could further improve selectivity for multiple fuel components. Portable FTIR units may allow field deployment for real-time biodiesel monitoring at distribution sites. Automation and connectivity with laboratory information management systems (LIMS) will streamline compliance reporting.

Conclusion

The enhanced FTIR method on the Agilent 5500t enables rapid, accurate quantification of biodiesel in diesel fuel from 0.025% to 5%. Its linear response, low detection limit, and ease of use make it well suited for industrial quality assurance and regulatory testing.