Determination of Off-Odor Compounds in Drinking Water Using an SPME Device with Gas Chromatography and Mass Spectrometry

Importance of the Topic

Off‐odor compounds such as 2‐methyl isoborneol (2‐MIB) and geosmin at parts‐per‐trillion levels compromise the sensory quality of drinking water and pose challenges for water utilities. Rapid and sensitive detection of these trace contaminants is essential for ensuring compliance with regulatory limits (10 ng/L in China GB5749‐2006) and providing early warning of water quality incidents.

Objectives and Study Overview

This study presents a fully automated headspace solid‐phase microextraction (SPME) Arrow method coupled with gas chromatography–mass spectrometry (GC/MS) for quantifying 2‐MIB and geosmin in drinking water. Key aims were to improve sensitivity over conventional sample preparation techniques, establish method robustness and reproducibility, and demonstrate applicability to real‐world water samples.

Methodology and Instrumentation

The analytical workflow uses an Agilent PAL3 RSI (or RTC) autosampler equipped with the SPME Arrow accessory (DVB/CAR/PDMS, 1.1 mm od). Samples (5 mL water + 1.5 g NaCl + internal standard) are incubated at 60 °C for 2 min, followed by 30 min headspace extraction. Thermal desorption at 250 °C for 5 min introduces analytes into an Agilent 7890B GC coupled to a 5977B single‐quadrupole MS. Chromatographic separation employs a DB-5MS UI column (30 m × 0.25 mm × 0.25 µm) under a temperature program from 60 °C to 270 °C. Detection in selected‐ion monitoring mode targets m/z 95, 107, 108 for 2-MIB; m/z 111, 112, 125 for geosmin; and m/z 94, 124 for the internal standard.

Main Results and Discussion

• Sensitivity: Method detection limits of 0.37 ng/L for 2-MIB and 0.22 ng/L for geosmin (MDL calculated over eight replicates at 2 ng/L).
• Linearity: Calibration over 1–100 ng/L yielded correlation coefficients above 0.999 for both analytes.
• Precision: Intraday repeatability (n=5 at 10 ng/L) showed RSDs of 1.65% (2-MIB) and 3.7% (geosmin); interday RSDs over five days were 5.24% and 8.57%, respectively.
• Real‐sample performance: Tap water spiked at 10 ng/L gave recoveries of 116% (2-MIB) and 98.4% (geosmin) with RSDs below 4%.

Benefits and Practical Applications

The SPME Arrow‐GC/MS method offers solvent‐free, green extraction with high throughput and minimal matrix interference. The rugged Arrow device ensures long lifetime and consistent performance, making it suitable for routine monitoring and online control systems in water treatment plants.

Future Trends and Opportunities

The integration of SPME Arrow with automated sample handlers is poised to expand to other trace organic contaminants, including emerging taste and odor compounds. Coupling with high‐resolution MS or tandem MS may further enhance selectivity and lower detection limits. Advances in sorbent chemistries and miniaturized GC/MS platforms will support field‐deployable analysis for rapid source‐water screening.

Conclusion

This application note demonstrates that SPME Arrow coupled with GC/MS provides a robust, sensitive and fully automated solution for tracking off‐odor compounds in drinking water. The protocol meets regulatory requirements, reduces solvent use, and yields high reproducibility, representing an effective tool for water quality laboratories.