MEASURING BIODIESEL ASTM 7371 and EN 14078 with the Agilent Cary 630 FTIR

Importance of the Topic

Biodiesel content in diesel affects engine performance, emissions, cold-flow properties and regulatory compliance. Accurate quantification is essential for quality control in fuel production, distribution and use across transport and industrial sectors.

Objectives and Overview

This article reviews two standardized infrared methods for determining biodiesel fraction in diesel fuel: ASTM D7371 (0–100% range using multivariate PLS calibration) and EN 14078 (0–10% range using linear peak-height measurement). It demonstrates implementation on the Agilent Cary 630 FTIR and summarizes dedicated turn-key analyzers (Agilent 4500 and 5500).

Methodology and Instrumentation

The methods rely on mid-IR detection of the biodiesel carbonyl band at 1745 cm⁻¹. ASTM D7371 uses a 5-bounce ZnSe ATR, three calibration curves for different biodiesel ranges (0–10%, 10–30%, 30–100%) and partial least squares regression. EN 14078 employs a 200 µm transmission pathlength (TumblIR accessory) and linear regression on carbonyl peak height.

Used Instrumentation

• Agilent Cary 630 FTIR engine with interchangeable 5-bounce ZnSe ATR and TumblIR modules
• TumblIR accessory (200 µm pathlength) for EN 14078 transmission measurements
• MicroLab PC software with built-in PLS models, conditional reporting and guided workflows
• Agilent 4500 Portable FTIR Analyzer (battery-operated) with fixed multibounce ATR or TumblIR and validated methods
• Agilent 5500 FTIR Analyzer for laboratory or industrial settings with fixed sampling interfaces and preloaded calibrations

Main Results and Discussion

Both methods run seamlessly on the Cary 630 by selecting the proper sampling interface and method file. TumblIR simplifies transmission sampling by eliminating bubble errors and reducing handling time. MicroLab PC automatically verifies accessory matches, prompts for cleanliness checks, performs background scans, acquires spectra, selects the correct calibration curve and calculates biodiesel content in seconds, minimizing user error.

Benefits and Practical Applications of the Method

• Fast, accurate biodiesel quantification for routine QA/QC
• Reduced analysis time and error potential with TumblIR accessory
• Automated workflows and visual pass/fail cues improve productivity
• Portability of the 4500 FTIR for field analysis and robustness of the 5500 FTIR for on-site and manufacturing environments

Future Trends and Possibilities of Use

Future developments may include expanded multivariate libraries to cover new biodiesel feedstocks, integration with cloud-based data management for remote monitoring, miniaturized inline FTIR modules for real-time production control and combined sensor platforms for comprehensive fuel property analysis.

Conclusion

Agilent’s FTIR portfolio enables standardized, reliable biodiesel measurement via ASTM D7371 and EN 14078. The Cary 630 offers flexibility through interchangeable accessories, while the 4500 and 5500 analyzers provide turnkey solutions with validated methods for both laboratory and field applications, ensuring high throughput and data integrity.

References

1. ASTM International. ASTM D7371: Test Method for Determination of Biodiesel Content in Diesel Fuel by FTIR Spectroscopy.
2. CEN. EN 14078: Determination of Total Fatty Acid Methyl Ester Content by Mid-Infrared Spectroscopy.
3. Agilent Technologies Inc. Application Note 5991-2241EN: Measuring Biodiesel with Agilent Cary 630 FTIR. 2013.