Identifying Unknown Chemicals and Disinfection Byproducts in Swimming Pools and Hot Tubs

Significance of the Topic

Swimming pools and hot tubs rely on chemical disinfection to control pathogens. However these disinfectants react with organic matter and user introduced compounds to form disinfection byproducts (DBPs) that may pose health risks. Characterizing unknown DBPs is essential for optimizing water treatment and protecting public health.

Study Objectives and Overview

This study applied non targeted high resolution gas chromatography time of flight mass spectrometry (GC-HRT) to identify known unknown and unknown unknown DBPs in swimming pool and hot tub waters. Samples were collected along complete water pathways (source, finished, tap, pool, spa) to compare the emergence and transformation of halogenated species.

Methodology and Instrumentation

• Sample preparation included large volume extraction with Amberlite XAD resin, concentration, and diazomethane derivatization of halo acids.
• Instrumentation comprised Pegasus HT GC-TOFMS, Pegasus 4D GC×GC-TOFMS, and Pegasus GC-HRT with 25 000 mass resolution, m/z range 33–650, and 5 spectra/second acquisition.
• ChromaTOF HRT software enabled high resolution deconvolution of coeluting peaks.
• Mass defect plots (Cl-H) and combined electron ionization (EI) and chemical ionization (CI) accurate mass data (<1 ppm) supported identification of halogenated compounds.

Key Results and Discussion

• A diverse array of chlorinated and brominated byproducts including haloacetic acid esters, halophenols, brominated alkenes, and phosphate derivatives were detected in pool and spa waters but absent in source water.
• Mass defect plots effectively isolated regions for chlorinated, brominated, and mixed halogen species to guide targeted extraction of ion chromatograms.
• High resolution deconvolution resolved overlapping peaks, increasing the number of detectable compounds beyond nominal resolution methods.
• Library similarity matches and accurate mass fragmentation patterns enabled tentative identification of both known unknowns (library hits >800/1000) and previously unreported unknowns.

Benefits and Practical Applications

• The non targeted GC-HRT workflow provides comprehensive profiling of complex matrices, revealing a broader spectrum of DBPs than targeted approaches.
• High resolution deconvolution and mass accuracy ensure confident detection and structural proposals, supporting risk assessment and regulatory compliance.
• The approach can be integrated into routine water quality monitoring to optimize disinfection protocols while minimizing harmful byproducts.

Future Trends and Opportunities

• Expansion of high resolution spectral libraries and automated identification algorithms will improve confidence in unknown annotation.
• Combining GC-HRT with complementary techniques such as LC-HRMS and ion mobility may capture polar or thermolabile byproducts.
• Real time online monitoring and machine learning based pattern recognition could enable proactive control of disinfection conditions.
• Correlation of DBP profiles with toxicological data will refine risk assessments and inform safer water treatment strategies.

Conclusion

The application of high resolution non targeted GC-HRTMS combined with high resolution deconvolution and mass defect analysis effectively identified a wide range of disinfection byproducts in swimming pool and hot tub waters. This comprehensive approach enhances our understanding of DBP formation and provides a robust framework for improving water quality management.

References

• Byer JD, Richardson SD, Daiber EJ, Chowdary SA, Binkley J, Patrick J. Identifying Unknown Chemicals and Disinfection Byproducts in Swimming Pools and Hot Tubs. LECO Corporation and University of South Carolina.