Meeting the Requirements of EN12916:2006 (IP391/07) Using Agilent 1200 Series HPLC Systems

Importance of the topic

Diesel fuel performance is critically determined by its aromatic content and ignition quality, expressed as the cetane number. Controlling mono-, di- and polycyclic aromatics in conventional and biodiesel-blended fuels ensures optimal engine performance, compliance with environmental standards and extended equipment life.

Objectives and study overview

This study demonstrates the application of EN12916:2006 (IP391/07) for quantifying aromatic hydrocarbon classes in diesel and diesel/biodiesel blends using an Agilent 1200 Series HPLC system with refractive index detection. The aim is to validate system suitability, separation selectivity and quantitation accuracy across specified concentration ranges.

Methodology and instrumentation

Samples and calibration standards are prepared in n-heptane according to IP391/07. Separation is achieved by normal-phase HPLC on serially connected amino and cyano stationary phases with an isocratic n-heptane mobile phase. Two system calibration mixtures, SCS1 and SCS2, verify resolution, elution order and lack of interference from fatty acid methyl esters (FAME) up to 5% v/v. Quantitation relies on refractive index detection and external calibration across four concentration levels.

Used Instrumentation

• Agilent 1200 Series LC system
• G1312B binary pump (normal-phase seals)
• G1367C autosampler with needle wash
• G1316C thermostatted column compartment (25 °C)
• G1362A refractive index detector
• Agilent ChemStation software B.04.01
• ZORBAX NH2 (4.6×150 mm, 5 μm) and SB-CN (4.6×150 mm, 5 μm) columns in series
• n-Heptane, HPLC grade

Main results and discussion

The method achieved baseline separation of key markers (cyclohexane, 1-phenyldodecane, o-xylene, hexamethylbenzene, naphthalene, dibenzothiophene, 9-methylanthracene, chrysene and FAME). Resolution between cyclohexane and o-xylene met the IP391/07 requirement (R between 5.7 and 10). Calibration curves for representative analytes exhibited linearity R² ≥ 0.9999 with intercepts below 0.01 g/100 mL. Retention time and peak area precision yielded RSDs ≤ 0.06% (aromatics) and ≤ 3.2% (tri+ aromatics). Real diesel and B5 blends showed consistent aromatic content across multiple vendors, demonstrating robustness.

Benefits and practical applications

• Full compliance with EN12916:2006 (IP391/07) without backflush requirements
• Reliable separation of aromatics and FAME in B5 blends
• High precision and linearity for quality control and regulatory testing
• Simple isocratic operation with minimal solvent consumption

Future trends and opportunities

Emerging needs include extending analysis to higher biodiesel blends, integrating rapid switching or gradient techniques to shorten run times, exploring alternative detectors (UV, ELSD) for enhanced sensitivity and coupling with mass spectrometry for compound identification. Automation and inline solvent drying can further improve throughput and column longevity.

Conclusion

The Agilent 1200 Series HPLC system satisfies all IP391/07 performance criteria for aromatic hydrocarbon determination in diesel and low-level biodiesel blends. The method delivers accurate, precise and reproducible results, making it a robust solution for industrial and regulatory laboratories.

References

• ASTM D6591-06 and D6379-04
• IP391/07, Energy Institute (Institute of Petroleum Test Methods)
• EN12916/06, Energy Institute (Institute of Petroleum Test Methods)
• Agilent Technologies publication 5965-9044EN (1997)