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

Significance of the topic

The integration of biodiesel into petroleum diesel is increasingly common due to economic and environmental drivers. However, even low levels of biodiesel can affect fuel stability, engine performance, and promote microbial growth during storage. Regulatory bodies differ in their limits and reporting requirements, creating a critical need for reliable, low-level detection methods to ensure fuel quality and compliance.

Objectives and Overview

This study adapts the EN 14078 FTIR method on the Agilent 5500t spectrometer to achieve quantitative detection of biodiesel in diesel at concentrations from 0.025 % to 5 % (v/v). The aim is to extend the original 1 %–10 % range down to trace levels, offering a user-friendly, rapid analytical approach for industries requiring stringent quality control.

Methodology

Standards spanning 0 % to 1.5 % biodiesel were prepared by serial dilution. Measurements were performed in triplicate on two separate Agilent 5500t instruments using a 100 µm path-length transmission cell. Each sample acquisition involved 32 scans at 4 cm⁻¹ resolution, yielding a 15-second analysis time. Calibration employed the carbonyl absorption band at 1745 cm⁻¹, with peak area (rather than peak height) to enhance sensitivity at low concentrations.

Used Instrumentation

• Agilent 5500t FTIR spectrometer
• 100 µm Tumbler transmission cell
• MicroLab software for calibration and prediction

Main Results and Discussion

The carbonyl band at 1745 cm⁻¹ was detectable down to 0.025 % biodiesel, with absorbance values clearly distinguished from the blank. Calibration across 0–1.5 % yielded a linear response (R² = 0.9998). Validation over 0–5 % biodiesel produced an average relative error of 1 % and a maximum error of 2 %, demonstrating the method’s accuracy and robustness beyond the initial calibration range.

Benefits and Practical Applications

• Fast, reproducible quantification with sub-0.05 % detection limits
• Embedded EN 14078 method eases user implementation
• Applicable for storage monitoring, regulatory compliance, and QA/QC in fuel distribution

Future Trends and Applications

Enhanced chemometric approaches could further lower detection limits and improve specificity. Integration of inline FTIR sensors offers real-time monitoring in storage tanks or supply pipelines. The method may extend to other biofuel blends and quality parameters, supporting evolving regulatory and industrial needs.

Conclusion

The modified EN 14078 method on the Agilent 5500t FTIR spectrometer provides a sensitive, rapid, and user-friendly solution for low-level biodiesel detection in diesel fuel. It meets stringent accuracy requirements, supports diverse industry applications, and addresses regulatory challenges across global markets.

Reference

• Higgins F. Low level detection of biodiesel in diesel fuel using the Agilent 5500t FTIR spectrometer Application Note. Agilent Technologies; Publication 5990-7803EN; 2011.
• EN 14078:2009. Solid phase FTIR determination of biodiesel in diesel fuel.
• ASTM D975:2011. Standard Specification for Diesel Fuel Oils.