AUTOMATING SAMPLE PREPARATION FOR THE GC ANALYSIS OF BIODIESEL USING METHOD

Importance of the Topic

Automating the preparation of calibration standards and samples for GC analysis based on EN14105 ensures accurate determination of free and total glycerol as well as mono-, di-, and triglycerides in biodiesel. This process is essential for maintaining fuel quality, regulatory compliance, and reducing manual labor, waste, and operational costs.

Objectives and Study Overview

The study demonstrates the adaptation of the EN14105 derivatization and GC method to the Agilent 7696A WorkBench to:

• Automate the preparation of calibration standards and samples at a tenth scale
• Maintain method performance criteria including calibration linearity and precision
• Reduce reagent use and waste generation

Methodology

The EN14105 method involves derivatizing nonvolatile glycerol and glycerides to volatile silyl-derivatives prior to GC analysis. Sample preparation steps adapted to the WorkBench include:

• Weighing or pipetting scaled quantities of biodiesel into 2-mL vials
• Adding internal standard (1,2,3-butanetriol) and stock glyceride solutions
• Derivatizing with MSTFA and pyridine for 15 minutes
• Quenching reactions with heptane

Instrumentation

• Agilent 7696A WorkBench with 7693A injection towers for automated liquid transfers and vial handling
• Agilent 7890A gas chromatograph equipped with a cool-on-column inlet and flame ionization detector
• Helium carrier gas at defined pressures and flows
• Robotic arm, vortex mixer, and heating station integrated in the WorkBench

Main Results and Discussion

Calibration standards prepared automatically showed excellent linearity with correlation coefficients meeting or exceeding EN14105 criteria. Ten replicate B100 biodiesel samples yielded:

• Relative standard deviation below 2% for glycerol quantification
• Reproducible monoglyceride, diglyceride, and triglyceride measurements
• Consistent total glycerin values with minimal variance

Overlay chromatograms confirmed stable retention times across multiple runs. Automated preparation reduced human error and improved throughput while maintaining method accuracy.

Benefits and Practical Applications

• Significant reduction in reagent consumption and chemical waste
• Higher sample throughput and reproducibility
• Lower labor costs and minimized manual pipetting errors
• Compliance with EU biodiesel standards for quality control laboratories

Future Trends and Potential Applications

Automation of derivatization and sample handling can be extended to other lipid analysis methods and biofuel quality protocols. Integration with in-line weighing or spectroscopic checks may further enhance accuracy. Development of miniaturized workflows could drive sustainable high-throughput testing in industrial and research settings.

Conclusion

The adaptation of the EN14105 method to the Agilent WorkBench demonstrates reliable automation of biodiesel sample preparation at reduced scale. The approach maintains method performance, lowers costs, and offers a robust solution for routine analysis in compliance with regulatory standards.

References

1. DIN EN14105:2011-07 Fat and Oil Derivatives – Fatty Acid Methyl Esters – Determination of Free and Total Glycerol and Mono-, Di-, and Triglyceride Contents European Committee for Standardization