Analysis of Diesel Range Organics (DRO) and Motor/Lube Oil Range Organics (ORO) in Ultrashort Run Time

Significance of the Topic

The rapid and accurate quantification of diesel range organics (DRO) and motor/lube oil range organics (ORO) is critical for environmental monitoring and remediation efforts. Traditional methods require long run times and expensive carrier gases, limiting laboratory throughput and increasing operational costs.

Objectives and Study Overview

This study aimed to develop an ultrafast gas chromatography (GC) method capable of separating C10–C40 hydrocarbons in under 2 minutes using a resistively heated fast temperature programmable (FTP) column and to evaluate hydrogen as a cost-effective alternative to helium as the carrier gas.

Methodology and Instrumentation

• Sample Preparation: Diesel #2 and motor oil standards were diluted in dichloromethane to 10–500 ppm for five-point calibration.
• Instrumentation: Shimadzu GC-2030 with split/splitless injector, flame ionization detector (FID), AOC-20 Plus autosampler, FTP-MXT-1 resistively heated column, and a gas selector for automated He/H₂ switching.
• Chromatographic Conditions: 0.1 µL splitless injection; constant flow of 10 mL/min; column temperature ramp from 40 °C to 350 °C at 280 °C/min; FID at 370 °C; data acquisition via LabSolutions software.

Main Results and Discussion

• Separation Efficiency: Complete elution of C10–C40 hydrocarbons in approximately 1.5 minutes, supporting up to 250 analyses per 12-hour shift.
• Carrier Gas Comparison: Hydrogen reduced retention times relative to helium while maintaining comparable detector response and resolution (USP > 1.3).
• Calibration Performance: Linear response over 10–500 ppm with coefficients of determination (r²) > 0.997 and accuracy within 15 % of expected values for both DRO and ORO.

Benefits and Practical Applications

This ultrafast GC-FID approach offers an order-of-magnitude increase in throughput compared to EPA Method 8015, automated carrier-gas switching to minimize downtime, and a lower-cost hydrogen alternative to helium. It supports rapid site screening and routine environmental analysis workflows.

Future Trends and Opportunities

• Integration of overlapping autosampler functions to reduce cycle times below 3 minutes per sample.
• Coupling resistively heated columns with mass spectrometric detection for enhanced compound identification.
• Development of field-deployable ultrafast GC systems for on-site environmental monitoring.
• Extension of ultrafast methodologies to other classes of semivolatile contaminants.

Conclusion

The ultrafast GC-FID method employing a resistively heated FTP column and hydrogen or helium carrier gas achieves reliable DRO and ORO quantification in under 2 minutes, substantially improving laboratory throughput and offering a cost-effective alternative to established protocols.

References

• U.S. EPA. 2003. Method 8015D (SW-846): Nonhalogenated Organics Using GC/FID, Revision 4.