Optimisation and validation of an ITSP method for the determination of Taste and Odour compounds in water

Importance of the Topic

This work addresses the critical need for sensitive and high‐throughput analysis of trace taste and odour compounds (TOCs) in drinking water. Due to extremely low odour thresholds (ng/L), these analytes require robust enrichment and detection strategies to ensure water quality and public confidence.

Objectives and Study Overview

The study aimed to refine a fully automated Instrument Top Sample Preparation (ITSP) workflow for TOC determination. Key goals included:

• Streamlining sample preparation for high throughput
• Evaluating acetone versus dichloromethane as elution solvents
• Establishing method performance across diverse water matrices

Methodology and Instrumentation

Automated sample preparation involved transferring 35 mL water samples into amber vials, adding NaCl and methanol, then processing on a Gerstel Multipurpose Sampler (MPS) 2 XL with dual heads. One head performed ITSP enrichment using 2.5 mL headspace syringes, while the other injected 10 µL of extract into a Gerstel Cooled Injection System (CIS 4). Analysis was conducted on an Agilent 7890B GC coupled to a 7010 Triple Quadrupole MS in Selected Reaction Monitoring (SRM) mode. Key GC/MS settings:

• Column: Agilent DB-5MS Ultra Inert 30 m × 0.25 mm × 0.25 µm
• Carrier gas: He at 1 mL/min
• CIS inlet: 10 µL large volume injection, solvent vent mode
• EI source with nitrogen collision gas at 1.5 mL/min

Main Results and Discussion

Optimization showed comparable recoveries for acetone and dichloromethane, but acetone provided superior reproducibility (RSD 5–13% vs. 16–22%). Calibration curves exhibited excellent linearity (R2 ≥ 0.989) over 1–25 ng/L, with limits of detection between 0.6 and 1.1 ng/L. Validation across five water types (RO, soft, medium, hard, surface) at four spike levels delivered consistent recoveries and RSDs of 6–10%, demonstrating strong matrix tolerance.

Benefits and Practical Applications

The automated ITSP‐GC/MS method offers:

• Enhanced throughput and reproducibility
• Low detection limits suitable for regulatory monitoring
• Reduced reliance on chlorinated solvents

Future Trends and Potential Applications

Further developments may include miniaturized cartridges for field deployment, integration with high‐resolution MS for broader compound panels, and adaptation to real‐time monitoring platforms. Advances in green solvents and automated data processing will continue to expand method applicability.

Conclusion

The optimized ITSP workflow coupled with GC‐MS provides a robust, sensitive, and high‐throughput solution for trace TOC analysis in drinking water. Acetone proved an effective solvent alternative, and the method showed excellent reproducibility and matrix compatibility.

Reference

1. Gardner M. and Wilson A., Manual on analytical quality control for the water industry, NS30, WRC, 1989.