Trace analysis of pharmaceuticals and organic contaminants in water

Significance of the topic

Trace levels of pharmaceuticals, personal care products and endocrine disrupting compounds in drinking water present emerging health concerns. Conventional treatment methods may not remove these contaminants effectively, leading to detectable concentrations in the low parts-per-trillion range. Reliable, sensitive and high-throughput analytical approaches are essential to monitor water quality and validate the performance of new point-of-use treatment technologies.

Study objectives and overview

This application note evaluates the performance of an online pre-concentration liquid chromatography system (EQuan MAX Plus) coupled to a triple quadrupole mass spectrometer (TSQ Endura) for quantitative analysis of eight target organic contaminants in drinking water. The goal is to achieve quantitation limits at or below one-sixth to one-fourth of the Maximum Effluent Concentration (MEC) defined by NSF/ANSI Standard 401, demonstrating accuracy, reproducibility and speed using 1 mL injections.

Methodology and instrumentation

The workflow combines an online solid phase trapping column with rapid gradient elution on analytical columns tailored for positive or negative electrospray ionization. Target analytes include estrone, ibuprofen, nonylphenol, naproxen (negative ion mode) and trimethoprim, phenytoin, linuron, atenolol (positive ion mode). Gradient conditions, mobile phases and MS selected reaction monitoring (SRM) transitions were optimized to ensure low background and clear signal. Key instrumentation:

• EQuan MAX Plus online pre-concentration LC system
• TSQ Endura triple quadrupole mass spectrometer with heated-ESI
• Accucore aQ and Hypersil GOLD aQ analytical columns
• TraceFinder software for data acquisition and quantitation

Results and discussion

Calibration curves for all analytes exhibited linear response down to concentrations well below the MEC, with correlation coefficients exceeding 0.99. Example SRM chromatograms at 10× MEC demonstrated clear separation and target ion detection. Reproducibility studies using seven replicate injections at 0.37× MEC in fresh tap water yielded relative standard deviations (RSDs) below 12% for all compounds. Customer-supplied samples stored for extended periods showed greater signal loss and variability, highlighting the need for fresh sample analysis.

Contributions and practical applications

This method delivers rapid, high-sensitivity quantitation of trace contaminants in drinking water with minimal sample preparation time (minutes versus hours for offline SPE). It supports compliance testing, treatment efficacy evaluation and routine environmental monitoring in municipal and point-of-use applications.

Future trends and potential applications

Advancements in online pre-concentration and timed-SRM acquisition promise further improvements in detection limits and throughput. Integration with automated sampling platforms could streamline field testing. Expanding the compound panel to include additional emerging contaminants will address evolving regulatory and public health needs.

Conclusion

The EQuan MAX Plus LC system combined with the TSQ Endura mass spectrometer enables reliable, accurate quantitation of emerging organic contaminants at parts-per-trillion levels in drinking water. Fresh sample preparation is critical to maintain method performance. This approach supports fast, reproducible analysis for environmental monitoring and treatment verification.

Reference

1. NSF/ANSI Standard 401. Emerging Compounds and Incidental Contaminants in Drinking Water Treatment Units.