MINERAL OIL/TPH

Significance of the Topic

Monitoring total petroleum hydrocarbons (TPH) in environmental matrices is crucial for assessing contamination, regulatory compliance, and site remediation. Ultra-fast gas chromatography (GC) offers rapid throughput, enabling high sample volumes with reliable quantification of complex hydrocarbon mixtures without detailed compound separation.

Objectives and Study Overview

This study demonstrates a method for determining TPH in soil using the Agilent Intuvo 9000 GC system. Key objectives include evaluating the speed, accuracy, and precision of ultra-fast GC for TPH analysis in a certified reference soil sample. Duplicate analyses and consensus-certified material ensured robust method validation.

Methodology and Instrumentation

Sample preparation followed ISO 16703 procedures with solvent extraction and cleanup of a BAM-U021 certified soil reference containing 3,560± 260 mg/kg mineral oil hydrocarbons. GC conditions were optimized for ultra-fast performance: splitless injection at 350°C (0.5 μl), helium carrier at 10 mL/min, temperature program from 40°C (0.5 min) to 350°C at 250°C/min with a 1.3-minute hold. Detection was by flame ionization at 350°C.

Used Instrumentation

• Agilent Intuvo 9000 Gas Chromatograph
• Direct column heating technology enabling rapid thermal ramps and cool-down
• Electronic Pneumatics Controller (EPC) for consistent high carrier flow
• Flame Ionization Detector (FID)

Key Results and Discussion

Five replicate injections of each duplicate soil extract were completed in approximately 3 minutes per run. Key findings include:

• Mean TPH concentrations: sample A 3,500 mg/kg, sample B 3,484 mg/kg versus certified 3,560± 260 mg/kg.
• Precision demonstrated by RSDs below 1% for both duplicates (0.82% and 0.15%).
• Single-lab repeatability (r) at 59 mg/kg well under the reference limit of 139 mg/kg.

Overlay chromatograms showed consistent retention times for C10 (0.747 min) and C44 (1.804 min) markers, confirming repeatability and instrument stability.

Benefits and Practical Applications

• High sample throughput with run times under 3 minutes accelerates processing of large environmental batches.
• Robust accuracy and precision support regulatory compliance and site assessment.
• Reduced instrument cycle time lowers operational costs and maintains laboratory productivity.
• Method aligns with international standards (ISO 16703) for TPH in soil.

Future Trends and Potential Applications

Potential developments include:

• Integration with automated extraction systems for seamless high-throughput workflows.
• Coupling with mass spectrometry or advanced detectors for improved compound specificity.
• Extension of ultra-fast GC methods to water, air particulate, and biota analyses.
• Application of chemometric and machine learning tools for chromatogram deconvolution and quality assurance.

Conclusion

The ultra-fast GC method using Agilent Intuvo 9000 GC delivers rapid, accurate, and precise TPH determination in soil. Innovative column heating and stable pneumatic control enable high-throughput analysis under 3 minutes per sample while meeting stringent performance criteria.

References

1. ISO 16703:2004(E). Soil quality – Determination of content of hydrocarbon in the range C10 to C40 by gas chromatography. Geneva, Switzerland: International Organization for Standardization.