Comparison of EG-Silicone-SBSE and Derivatization-PDMS-SBSE for the Analysis of Phenolic Compounds and Off-fl avors in Water

Significance of the Topic

Monitoring phenolic and off-flavor compounds in drinking water is critical due to their potential health risks and impact on taste and odor. Chlorophenols generated during water chlorination may function as endocrine disruptors or carcinogens at trace levels, while geosmin and 2-methylisoborneol (MIB) produce detectable odors below parts-per-trillion thresholds. Regulatory bodies such as the EU and EPA enforce stringent limits on phenolic contaminants, driving the need for highly sensitive and reliable analytical techniques.

Objectives and Study Overview

This study evaluates and compares two solvent-free stir bar sorptive extraction (SBSE) strategies coupled with thermal desorption gas chromatography–mass spectrometry (TD-GC/MS) for quantifying 16 phenolic compounds and three off-flavor analytes. Method 1 employs in-situ acetylation derivatization followed by SBSE using a PDMS Twister. Method 2 uses direct SBSE without derivatization on an EG-Silicone Twister. Both approaches were assessed across a 0.01–1 µg/L calibration range.

Methodology and Instrumentation

Sample preparation involved 10 mL water aliquots adjusted to pH 4. For PDMS Twisters, 0.5 mL acetic anhydride and potassium carbonate were added for acetylation prior to 2 h SBSE at room temperature. EG-Silicone extractions required no derivatization. Both SBSE steps used magnetic stirring. Desorption occurred in a GERSTEL Thermal Desorption Unit with a Cooled Injection System (CIS 4) inlet, interfaced to an Agilent 7890A GC–5795 MSD. PDMS Twisters were thermally desorbed at 270 °C; EG-Silicone at 220 °C. GC columns were Rxi-5ms for PDMS and Stabilwax-DA for EG-Silicone extractions.

Main Results and Discussion

Both approaches achieved excellent linearity (R² > 0.993 for PDMS; > 0.996 for EG-Silicone) and repeatability (RSD 1.0–13.6 % and 0.7–11.8 %, respectively). Limits of detection ranged from 0.011 to 0.053 µg/L (PDMS) and 0.007 to 0.036 µg/L (EG-Silicone); LOQs remained below 0.16 µg/L. EG-Silicone recoveries varied from 17 to 127 % in line with log Kₒw values. Carryover was negligible after a second desorption cycle. Analysis of tap water samples confirmed applicability: Wakefield water contained geosmin (0.03 µg/L) and 2-methylphenol (0.028 µg/L), while Mülheim water showed no quantifiable phenolics.

Benefits and Practical Applications of the Method

SBSE-TD-GC/MS combines solvent-free extraction, minimal sample volume, high throughput, and automation. PDMS Twister with derivatization ensures compatibility with non-polar GC columns and robust long-term stability. EG-Silicone Twister streamlines sample prep by eliminating derivatization, facilitating straightforward recovery assessment. Both methods comply with strict drinking water regulations and support routine environmental monitoring.

Future Trends and Applications

Emerging developments may include novel polymer coatings for enhanced selectivity, coupling SBSE with comprehensive two-dimensional GC or high-resolution MS for complex matrices, and portable SBSE devices for on-site water quality monitoring. Integration with automated sample handling and advanced data analytics will further improve throughput and decision-making in water treatment and environmental assessment.

Conclusion

The comparative study demonstrates that both PDMS SBSE with in-situ acetylation and direct EG-Silicone SBSE provide effective, sensitive, and repeatable analysis of trace phenols and off-flavor compounds in water. These methods deliver low detection limits, strong linearity, and seamless automation, ensuring compliance with regulatory standards and facilitating routine water quality control.

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