An automated approach for the determination of gasoline range organics (GRO) in water by gas chromatography coupled with static headspace sampling

Importance of the Topic

Gasoline range organics (GRO: C6–C10 hydrocarbons) frequently contaminate groundwater due to spills and leaks. Rapid, reliable quantitation of GRO at low concentrations is critical to environmental risk assessment and regulatory compliance.

Objectives and Study Overview

This study evaluates the performance of a Thermo Scientific TriPlus 500 HS autosampler coupled to a TRACE 1310 GC-FID for quantitative determination of GRO in water. Key metrics include linearity, sensitivity, precision, recovery, robustness, and compliance with Wisconsin DNR modified GRO and EPA 8015 C methods.

Methods and Instrumentation

• Autosampler and GC: Direct interfacing of TriPlus 500 HS with TRACE 1310 GC, Instant Connect SSL injector, and FID.
• Column: TraceGOLD TG-1MS (30 m × 0.32 mm × 3.0 µm).
• Headspace conditions: 10 mL vials incubated at 85 °C for 30 min with fast shaking; vial pressurization at 200 kPa N2; 1 mL sample loop at 105 °C.
• GC program: 50 °C (1 min) ramp to 220 °C at 15 °C/min (hold 5 min).
• Carrier gas: He at 5 mL/min; FID at 300 °C with air (350 mL/min), H2 (35 mL/min), N2 (40 mL/min).
• Data processing: Chromeleon CDS v7.2 with automated workflows for blank subtraction, integration, and reporting.

Main Results and Discussion

• Linearity: Seven-point calibration (6.25–10 000 µg/L) yielded R² = 1.000 and response factor RSD <6.5% for individual and total-area integration.
• Sensitivity: Method detection limits (MDL) averaged 1.4 µg/L and LOQs averaged 4.6 µg/L, well below regulatory LOQ requirements.
• Recovery: Tap water spiked at 12.5 µg/L achieved 92–117% recoveries. Spikes at 1 000 and 10 000 µg/L in raw gasoline matrix delivered 89–116% recoveries. Automated matrix correction enhanced accuracy.
• Precision: Ten consecutive injections of spiked water showed peak area RSDs of 0.91% (standard mix) and 1.1% (raw gasoline). No carry-over detected in blanks.

Benefits and Practical Applications

• Minimal sample prep: direct headspace extraction eliminates solvents and reduces labor.
• High throughput: fast GC ramp and 240-vial capacity enable unattended 24 h operation.
• Robust operation: inert flow paths and precise pneumatics ensure reproducible injections and zero carry-over.
• Versatile quantitation: supports single-component and total-area integration for various regulatory protocols.

Future Trends and Opportunities

• Integration with HS-GC-MS for enhanced selectivity in complex matrices.
• AI-driven data review and automated compliance reporting.
• Development of portable headspace modules for on-site GRO screening.

Conclusion

The TriPlus 500 HS autosampler with TRACE 1310 GC-FID delivers a rapid, sensitive, and reproducible approach for GRO analysis in water. Validated linearity, low detection limits, high recoveries, and excellent precision confirm its suitability for routine environmental monitoring.

Reference

• Chromeleon CDS v7.2; Wisconsin DNR Modified GRO method; EPA 8015 C.