Using Stir Bar Sorptive Extraction (SBSE) for Taste and Odour Measurements in Drinking Water

Importance of the Topic

Ensuring the safety and palatability of drinking water requires reliable detection of trace taste and odour compounds. Traditional extraction methods often involve lengthy procedures, high solvent consumption and risk of sample degradation. Stir Bar Sorptive Extraction (SBSE) offers a streamlined, sensitive and environmentally friendly alternative that can improve laboratory productivity and field sampling integrity.

Study Objectives and Overview

This work presents the application of SBSE, marketed as Twister, for measuring trace taste and odour (T&O) contaminants in drinking water. The goals are to compare SBSE with conventional liquid–liquid and solid-phase extraction, demonstrate analytical performance for key odorants, and highlight practical benefits including automation and on-site sampling.

Methodology and Instrumentation Used

SBSE employs a magnetic stir bar coated with a polydimethylsiloxane (PDMS) phase to extract analytes directly from water samples. Key steps include:

• Insertion of Twister into the water sample and stirring (1–2 hours at 1 500 rpm).
• Rinsing with deionized water, drying and placement into a thermal desorption unit (TDU) tube.
• Automated thermal desorption in a GERSTEL TDU coupled to a cooled injection system (CIS), followed by GC-MS analysis on an Agilent 6890/5973 or equivalent.

The autosampler (MPS Multi-Purpose Sampler) enables parallel processing of multiple twisters. Variations include dual SBSE for polar and nonpolar fractions, an ethylene glycol–modified stir bar for polar analytes, and optional olfactometry with real-time voice-annotated detection.

Main Results and Discussion

SBSE achieved detection limits in the low ng/L range for key odorants such as geosmin, MIB and chlorinated phenols. Reproducibility ranged from 4 % to 15 % relative standard deviation. Parallel extraction on multi-position stir plates combined with automated desorption reduced total hands-on time and minimized solvent use to near zero. On-site extraction at distribution taps preserved sample integrity and captured transient events. Integrating olfactory detection provided direct sensory correlation, enhancing the identification of complaint compounds.

Benefits and Practical Applications

SBSE offers multiple advantages:

• High throughput: parallel extraction and automated analysis reduce turnaround time.
• Cost efficiency: minimal consumables, low per-sample cost and reusable stir bars (≥50 uses).
• Green chemistry: elimination of organic solvents and reduced lab waste.
• Enhanced sensitivity: ng/L detection without additional preconcentration.
• Versatility: applicable to pesticides, PAHs, nitrosamines and a wide range of water-borne analytes.

Future Trends and Applications

Emerging developments include coupling SBSE with high-resolution GC-QTOF for non-target screening and accurate mass confirmation, on-tap samplers for continuous monitoring, and further miniaturized automation like micro-SPE integration. Advanced data analytics and machine learning may be applied to combined chemical-olfactory datasets for rapid source identification and trend analysis.

Conclusion

Stir Bar Sorptive Extraction represents a powerful, user-friendly approach for trace T&O analysis in drinking water. Its combination of sensitivity, automation, low environmental impact and field deployability addresses many limitations of traditional methods. Continued innovation in sorbent chemistry and hyphenated instrumentation will broaden its utility across environmental and industrial analytical applications.