High Throughput Multi-Residue Screening of Drinking Water using the SPE-DEX~ and Pegasus GC-TOF-MS

Significance of the Topic

The rapid detection of multiple contaminants in drinking water is critical for ensuring water safety and regulatory compliance. Accelerating sample turnaround while maintaining robust qualitative screening is essential in water analysis laboratories.

Aims and Study Overview

This application note demonstrates the integration of an automated solid phase extraction system with time of flight mass spectrometry for high throughput multi-residue screening of drinking water. The study evaluates qualitative performance across diverse analyte classes spiked at low microgram per liter levels.

Methodology and Instrumentation

• Sample preparation involved spiking one liter of dechlorinated tap water with target compounds at 1 to 10 micrograms per liter followed by acidification to pH 2.
• An automated SPE-DEX 4790 device pre-conditioned and extracted analytes using a 50 mm hydrophilic disk and delivered extracts in dichloromethane.
• A DryDisk hydrophobic membrane removed residual water from extracts without chemical drying reagents.
• Analysis was performed by GC separation on an Agilent 6890 with a narrow bore column and rapid oven ramp, coupled to a LECO Pegasus III time of flight mass spectrometer.
• Automated data processing used peak finding and mass spectral deconvolution algorithms to extract clean spectra and identify compounds.

Main Results and Discussion

• The combined SPE-DEX and DryDisk workflow reduced total analysis time from 2–3 hours to approximately 30 minutes per sample.
• A broad range of analytes was recovered, including phenols, triazines, organochlorine and organophosphorous pesticides, acids and volatile trihalomethanes.
• GC-TOF-MS acquisition at up to 500 spectra per second enabled full screening within 10 minutes and automated processing in under 2 minutes.
• Co-eluting pesticides were resolved within a 2 second retention time window and correctly identified with spectral match scores above 75 percent.
• Challenging compounds such as dichlorvos and azinphos isomers displayed good peak shapes and reliable identification at low concentration levels.

Benefits and Practical Applications

• High throughput qualitative screening supports faster decision making in water quality monitoring and contamination response.
• Fully automated extraction improves reproducibility and reduces manual workload.
• Rapid GC-TOF-MS analysis increases laboratory capacity and shortens sample turnaround time.

Future Trends and Opportunities

The promising qualitative performance suggests further development toward quantitative validation. Employing shorter GC columns and optimized flow conditions may achieve even faster analysis. Integration with laboratory information management systems could streamline data handling and reporting.

Conclusion

The combination of SPE-DEX and DryDisk extraction with Pegasus III time of flight mass spectrometry offers a rapid and reliable qualitative screening method for a wide range of drinking water contaminants. While the approach delivers substantial time savings and robust identification, further work on quantitative accuracy will extend its applicability to routine regulatory analysis.

References

• Scott S and Turner D Application Note No 098 High Throughput Multi-Residue Screening of Drinking Water Using SPE-DEX and Pegasus GC-TOF-MS GL Sciences