Determination of Odor Compounds in Water by SPME Arrow Gas Chromatography/Mass Spectrometry

Significance of the topic

Off‐odor compounds such as geosmin and 2‐methylisoborneol (2‐MIB) impart earthy or muddy tastes in drinking water at concentrations as low as single nanograms per liter. Trace monitoring of these metabolites, produced by cyanobacteria, is essential for safeguarding public health, ensuring regulatory compliance, and providing an early alert in case of water quality incidents.

Objectives and study overview

This work presents the development and validation of an automated headspace solid‐phase microextraction (SPME) Arrow coupled with gas chromatography–mass spectrometry (GC‐MS) for quantifying geosmin and 2‐MIB in drinking water. The goal was to achieve high sensitivity, reproducibility, and full compliance with Chinese hygienic standards (GB5749‐2006, GB/T 32470‐2016).

Methodology and instrumentation

The analysis was performed on an Agilent PAL3 RSI/RTC autosampler equipped with an agitator and Heatex stirrer, interfaced to an Agilent 7890B GC with 5977B single-quadrupole MS. A 1.1 mm OD SPME Arrow (DVB/CAR/PDMS) was conditioned at 270 °C, then used for headspace extraction of 5 mL water plus salt at 60 °C for 30 min. Desorption occurred at 250 °C for 5 min in splitless mode. Separation used a DB-5MS UI column (30 m×0.25 mm×0.25 µm) with temperature ramping from 60 °C to 270 °C. Detection in SIM monitored m/z 95, 107, 108 for 2‐MIB and m/z 111, 112, 125 for geosmin, with an internal standard at m/z 94 and 124.

Main results and discussion

Calibration was linear from 1 to 100 ng/L with R²>0.999 for both analytes. Intraday RSD values at 10 ng/L were 1.65% (2-MIB) and 3.70% (geosmin), and interday RSDs were below 8.57%. Method detection limits were 0.37 ng/L for 2-MIB and 0.22 ng/L for geosmin, with S/N ratios above 4 at 0.5 ng/L. Real tap water spiked at 10 ng/L yielded recoveries of 116% for 2-MIB and 98.4% for geosmin, with RSDs under 4% and no significant matrix interference.

Benefits and practical applications

• Exceptional sensitivity at sub-ng/L levels and broad dynamic range.
• Fully automated, solvent-free workflow minimizing operator exposure and waste.
• Robust Arrow design delivers extended service life and high sample throughput.
• Suitable for routine QA/QC in drinking‐water treatment plants and laboratories.

Future trends and opportunities

Advances may include on-site inline SPME Arrow integration, coupling with high-resolution or tandem MS for multi-analyte panels, microfluidic sample handling, and AI-driven spectral deconvolution. Such developments could enable real-time water quality monitoring and broader pollutant screening.

Conclusion

The SPME Arrow–GC-MS approach provides a fast, accurate, and robust solution for trace analysis of geosmin and 2-MIB in drinking water, fully satisfying Chinese national standards and offering a green, high-throughput alternative for water quality surveillance.

Reference

• China national standard GB/T 32470-2016: Method for determination of geosmin and 2-MIB in drinking water