LARGE VOLUME OIL IN WATER

Significance of the topic

The analysis of mineral oils in water is critical for environmental monitoring, as contamination near fuel stations and industrial sites can disrupt natural processes and threaten water quality. Regulatory demands for detecting low levels of oil hydrocarbons are increasing, requiring sensitive analytical techniques.

Objectives and overview of the study

This application note evaluates a programmable temperature vaporizer (PTV) large volume injection approach for gas chromatography to improve sensitivity and reduce sample preparation time in measuring mineral oil residues in aqueous matrices. The performance of an OPTIC 2 injector is compared with conventional splitless injection, highlighting detection limits and reproducibility.

Used methodology and instrumentation

• Instrumentation:
  OPTIC 2 injector with electronic pressure control mounted on an Agilent HP6890 GC, equipped with a 25 m × 0.32 mm i.d., 0.17 µm film Ultra-1 column.
• Injection technique:
  Solvent vent large volume injection in a packed liner (uncoated Supelcoport), allowing rapid 135 µL at-once injections and programmable venting to remove solvent before analyte transfer.
• GC conditions:
  Oven program starting at 35 °C (2 min hold), ramped at 15 °C/min to 350 °C; injector heated at 4 °C/s to 335 °C; split flow and vent parameters optimized via solvent monitoring.

Main results and discussion

Large volume injections of a 50-fold diluted alkane standard delivered chromatograms without significant peak discrimination compared to conventional 1 µL splitless injections. Reproducibility tests on C9–C40 alkanes showed relative standard deviations from 1.4 % to 5.9 %. Soil extracts from a gasoline station site were successfully analyzed, demonstrating the method’s robustness despite highly contaminated matrices.

Benefits and practical applications

• Enhanced sensitivity suitable for trace-level oil hydrocarbon detection in water and soil extracts.
• Reduced sample preparation time by eliminating solvent evaporation steps.
• Cost-effective automation due to durable packed liners and electronic pressure control.
• Compatibility with standard autosamplers without requiring speed-controlled injection.

Future trends and possibilities

The integration of large volume injection with advanced detectors and high-throughput GC systems could further lower detection limits and increase sample throughput. Emerging approaches may include coupling with mass spectrometry for compound-specific profiling and adapting PTV techniques for other challenging matrices such as wastewater and biota.

Conclusion

PTV-based large volume injection using the OPTIC 2 injector provides a reliable, sensitive, and automated solution for mineral oil analysis in environmental samples, combining high sample loads with reproducible chromatography and simplified workflow.