Determination of Benzene and Certain Derivatives in Water by Headspace Gas Chromatography (ISO 11423-1)

Importance of the Topic

Benzene and related aromatic compounds are common environmental contaminants in water with significant health and regulatory implications. Reliable analysis at trace levels is essential for monitoring water quality, ensuring compliance with international standards, and protecting public health.

Objectives and Overview

This application note demonstrates a headspace gas chromatography (HS-GC) method aligned with ISO 11423-1 for determining benzene and selected derivatives in aqueous samples. The goal was to showcase a single-injection approach on a dual-column, dual-FID system that meets required performance criteria.

Methodology

Samples were prepared by spiking ultrapure water with calibration standards ranging from 10 to 1,000 µg/L. Headspace conditions included an 80 °C equilibration, 1 mL sample loop, and helium as the carrier gas. The GC oven program started at 40 °C (8 min), ramped to 150 °C at 7 °C/min (3 min), then to 200 °C at 20 °C/min (5 min). Split injections (10:1) were performed into two capillary columns of differing polarity.

Instrumentation

• Agilent 7697A Headspace Sampler: 1 mL loop, 30 min equilibration at 80 °C
• Agilent Intuvo 9000 GC: inlet at 250 °C with ferrule-free splitter chip
• Columns: HP-5ms Ultra Inert (30 m × 0.32 mm, 0.25 µm) and HP-INNOWax (30 m × 0.32 mm, 0.25 µm)
• Detection: dual flame ionization detectors at 250 °C

Results and Discussion

Chromatograms of 15 target compounds at ~200 µg/L showed clear separation on both columns. Calibration curves across 10–1,000 µg/L exhibited correlation coefficients (R²) ≥ 0.9991. Repeatability (n = 7) yielded area RSDs of 1–4 %, typically below 2.4 % at mid-level. Method detection limits, calculated from a 2 µg/L standard, were ≤ 1.4 µg/L for all analytes. Recoveries in spiked tap water (~200 µg/L) ranged from 95 % to 102 %, satisfying ISO 11423-1 requirements.

Benefits and Practical Applications

By combining headspace sampling with dual-column FID detection, this approach enables simultaneous quantification and confirmation of benzene and derivatives in a single run. The ferrule-free inlet splitter offers rapid maintenance and reliable performance. Laboratories gain improved throughput, reduced solvent use, and compliance with international standards.

Future Trends and Applications

Advances may include integration with mass spectrometric detection for enhanced selectivity, miniaturized headspace systems for field analysis, and automated sample handling to further increase throughput. Method adaptations could target emerging contaminants and lower detection limits.

Conclusion

The Agilent Intuvo 9000 GC with a 7697A headspace sampler meets ISO 11423-1 criteria for benzene and aromatic derivative analysis in water. The method delivers excellent linearity, precision, low detection limits, and high recoveries in a streamlined workflow.

References

1. ISO 11423-1:1997 Water quality – Determination of benzene and some derivatives – Part 1: Headspace gas chromatographic method.