Implementation of novel SPME Arrow for the trace-level analysis of taste and odor compounds in drinking water

Importance of the Topic

Decaying algal blooms in water sources release earthy (“musty”) odor compounds such as 2-methylisoborneol (MIB) and geosmin. Although odor is regulated only as a secondary contaminant, accurate trace-level analysis of these compounds is essential for water utilities and environmental laboratories to manage taste and odor events and address consumer concerns.

Objectives and Study Overview

This study implements Standard Method 6040D using a novel SPME Arrow device instead of conventional SPME fibers. The goal is to evaluate sensitivity, robustness, and throughput of the SPME Arrow approach for quantifying MIB and geosmin at concentrations relevant to taste and odor thresholds (low ng/L).

Methodology and Instrumentation

Samples were prepared by spiking deionized water with NaCl (3 g per 10 mL) and known concentrations of MIB, geosmin, an internal standard (isobutyl-methoxypyrazine, IBMP), and a surrogate (isopropyl-methoxypyrazine, IPMP). Calibration standards ranged from 0.5 ng/L to 100 ng/L and were analyzed in triplicate with blanks interspersed. Extraction was performed using a PDMS/DVB/Carboxen SPME Arrow, followed by analysis on GC-MS.

Instrumentation Used

• Shimadzu GCMS-QP2020NX gas chromatograph–mass spectrometer
• Shimadzu AOC-6000 autosampler equipped for SPME Arrow
• SPME Arrow coating: PDMS/DVB/Carboxen

Results and Discussion

• Calibration: Both MIB and geosmin displayed excellent linearity (R² ≥ 0.99) across 0.5–100 ng/L.
• Reproducibility: At 10 ng/L, RSD was 15% for MIB and 12% for geosmin; at 0.5 ng/L, RSD improved to 0.2% (MIB) and 5% (geosmin).
• Limits of detection: Calculated at 0.05 ng/L (3× signal-to-noise), well below sensory thresholds (~20 ng/L for MIB, ~5 ng/L for geosmin).

Benefits and Practical Applications

The SPME Arrow method offers a rapid 30-minute analysis per sample by overlapping extraction with GC-MS runs. Its high sensitivity and reproducibility make it suitable for routine monitoring of taste and odor events in drinking water, enabling timely response by water treatment facilities and environmental laboratories.

Future Trends and Applications

Emerging directions include integration of SPME Arrow into fully automated workflows, development of novel sorbent coatings for broader analyte coverage, expansion to multi-compound screening, and potential field-deployable or online monitoring systems using advanced mass spectrometry techniques.

Conclusion

The novel SPME Arrow approach enhances trace-level analysis of MIB and geosmin in drinking water, delivering sub-threshold detection limits, robust reproducibility, and streamlined sample throughput, thereby supporting effective management of taste and odor events in water quality monitoring.