Automated Online SPE-UHPLC/MS/MS Analysis of Emerging Pollutants in Water

Importance of the Topic

Water resources are increasingly contaminated by trace organic pollutants originating from pharmaceuticals, personal care products (PPCPs), perfluoroalkyl substances (PFASs), and organophosphorus flame retardants (PFRs). These emerging contaminants can evade conventional treatment processes, accumulate in ecosystems, and pose risks to human health. Sensitive, high-throughput analytical methods are essential for routine monitoring, regulatory compliance, and risk assessment in drinking, surface, and wastewater effluent matrices.

Objectives and Study Overview

This study describes the development and validation of an automated online solid-phase extraction (SPE) coupled with ultrahigh-performance liquid chromatography/tandem mass spectrometry (UHPLC/MS/MS) method. The aims were to achieve simultaneous quantification of 87 analytes—58 PPCPs, 22 PFASs, and 7 PFRs—in diverse environmental water samples with minimal manual handling, broad analyte coverage, and excellent analytical performance.

Used Instrumentation

• Agilent 1260 Infinity II system: quaternary pump, binary pump, multisampler, and Quick Change 2-position/10-port valve.
• Two SPE cartridges (2.1×12.5 mm) alternately configured for loading and elution.
• Analytical columns: Poroshell 120 EC-C18 (3.0×50 mm, 2.7 µm) and ZORBAX Eclipse Plus C18 (4.6×50 mm, 3.5 µm).
• Agilent 6470A triple quadrupole LC/MS with ESI source operating in positive and negative modes.
• Agilent MassHunter software for acquisition and data analysis.

Methodology

Six SPE sorbents were screened across sample pH values (3, 7, 10) to identify a universal cartridge. The PLRP-S phase provided the highest recoveries across all target classes. Key extraction parameters included 1.8 mL sample loading at pH 7 with 0.05% formic acid aqueous washing. Chromatographic separation used a gradient of water and acetonitrile with 0.05% formic acid at 0.3 mL/min and a 30 °C column temperature. The mass spectrometer operated in dynamic MRM for optimized transitions, enabling separation of isobaric pairs and isomers.

Main Results and Discussion

The method delivered linear calibration (R² > 0.98) for 85 of 87 analytes over 1–200 ng/L. Limits of quantitation (LOQs) were below 10 ng/L for most compounds in drinking, surface, and wastewater effluent samples, with 65–76% of analytes achieving LOQs ≤ 5 ng/L in clean matrices. Recovery studies at 25 and 100 ng/L spiking levels showed 60–130% accuracy for over 87% of compounds, with precision (RSD) < 20%. Lower recoveries were mainly observed for long-chain PFASs, PFRs, and highly polar substances.

Benefits and Practical Applications

• High throughput: alternating dual SPE cartridges reduce cycle time.
• Broad analyte coverage: single method for multiple contaminant classes.
• Minimal manual preparation: improved reproducibility and reduced solvent consumption.
• Robust sensitivity: suitable for regulatory monitoring and environmental surveys.

Future Trends and Possibilities

Advances in online SPE-UHPLC/MS/MS could extend to additional classes of micropollutants, including neutral and zwitterionic compounds. Integration with high-resolution mass spectrometry may further enhance identification of unknowns. Automation and miniaturization trends will improve field deployability and real-time monitoring capabilities.

Conclusion

The automated online SPE-UHPLC/MS/MS approach provides a reliable, sensitive, and efficient platform for simultaneous determination of a wide range of emerging pollutants in environmental waters. Its strong analytical performance and high throughput make it a valuable tool for routine water quality monitoring and environmental research.

References

1. Dinh Q. T. et al. Rapid on-line enrichment and triple-quadrupole LC-MS/MS for antibiotics in river water. Talanta 2011.
2. Ferrer-Aguirre A. et al. On-line SPE-LC-MS/MS of emerging contaminants. J. Chromatogr. A 2016.
3. Mazzoni M. et al. On-line SPE-LC-MS/MS of PFAS in water. J. Anal. Methods Chem. 2015.
4. Anumol T. et al. Automated online SPE-LC-MS/MS for trace organics. Talanta 2015.
5. Wode F. et al. Multiresidue UHPLC-HRMS of 72 micropollutants in water. J. Chromatogr. A 2012.
6. Zhong M. et al. Online SPE-LC-MS/MS for PFAS, PPCPs, and PFRs in water. J. Chromatogr. A 2019.