ASTM D7806-12 for Biodiesel in Petroleum-based Diesel Fuel Oil

Importance of the Topic

The accurate determination of biodiesel (FAME) content in petroleum diesel is critical for quality control and regulatory compliance. Blended diesel fuels with biodiesel can affect engine performance, promote microbial growth, and accelerate oxidation, posing risks for stationary and critical power systems.

Objectives and Study Overview

This study demonstrates the application of ASTM D7806-12 using three portable and laboratory Agilent FTIR spectrometers (4500, 5500, Cary 630) to quantify biodiesel in diesel fuel over the range 1–30 vol %. It aims to validate method performance, including repeatability, accuracy, and ease of use both in laboratory and field settings.

Methodology and Instrumentation

The method employs two separate linear calibration models for 0–6 % and 6–30 % biodiesel concentrations. Calibration standards were prepared in three cetane-rated diesel stocks (low, high, ultrahigh) covering 0–30 % biodiesel. Spectra were collected (64 scans, 4 cm⁻¹ resolution) at defined pathlengths. Key spectral regions for FAME quantification are 1,713–1,784 cm⁻¹ (ester carbonyl) and 1,126–1,220 cm⁻¹ (C–O stretch). Models were implemented in Agilent MicroLab software with conditional reporting to select the appropriate calibration automatically.

Main Results and Discussion

The Agilent FTIR systems achieved repeatability better than ±0.02 % (X ±0.02 % vs. method requirement ±0.3 %). Qualification samples from 1–30 % biodiesel returned an average relative error of 0.6 % and maximum error of 1.9 %. Below 1 % biodiesel, error increased. Calibration models built separately for each cetane fuel stock outperformed combined models, reducing bias associated with fuel aromaticity and density differences.

Benefits and Practical Applications of the Method

• Rapid, non-destructive analysis for production and distribution QC of diesel/biodiesel blends
• Portable field deployment or laboratory implementation with consistent performance
• Automatic calibration selection and color-coded pass/fail reporting in MicroLab software
• Extended quantification range beyond 1–30 % using additional calibration models

Future Trends and Opportunities

Advances in miniaturized FTIR technology and machine-learning calibration may further improve sensitivity below 1 % and above 30 % biodiesel. Integration with remote monitoring networks could enable real-time fuel quality tracking at distribution and storage sites.

Conclusion

The Agilent 4500, 5500, and Cary 630 FTIR platforms meet or exceed ASTM D7806-12 requirements for biodiesel quantification in diesel. The method delivers high precision, accuracy, and operational flexibility, supporting both field and laboratory applications.

Instrumention Used

• Agilent 4500 FTIR with TumblIR sampling
• Agilent 5500 FTIR with DialPath sampling
• Agilent Cary 630 FTIR with TumblIR and DialPath

References

1. ASTM D7806-12, Standard Test Method for Determination of Biodiesel (FAME) in Diesel Fuel Oil by FTIR Spectroscopy
2. Mainali D., Rein A., Agilent Technologies Application Note, 2015