Analysis of Basic and Acidic Pharmaceutical Products in Drinking Water Using Online Sample Preparation and LC-MS/MS

Significance of the Topic

Pharmaceutical residues in drinking water have become a pressing environmental and public health concern. Beta blockers, painkillers, anticonvulsants and their metabolites enter surface and groundwater through human and veterinary use. Their polar metabolites often resist conventional treatments, posing risks to ecosystems and consumer safety. Reliable, sensitive and rapid analytical methods are essential for monitoring trace-level pharmaceuticals and ensuring water quality.

Objectives and Study Overview

This study aimed to develop and validate an online sample preparation combined with LC-MS/MS method for simultaneous analysis of 29 basic, neutral and acidic pharmaceuticals and metabolites in drinking water. Goals included minimizing sample preparation time, reducing sample volume and human error while maintaining high sensitivity and accuracy.

Methodology

• Sample Preparation: 10 mL water samples were filtered (0.2 µm), spiked with deuterated internal standards (sotalol-d6, carbamazepine-d10, diclofenac-d4) and processed automatically by the Thermo Scientific EQuan environmental quantitation system.
• Online Enrichment: Automated cleanup and preconcentration on a loading column, followed by valve switching to transfer enriched analytes onto the analytical column.
• Chromatography: Hypersil GOLD Phenyl column (50×2.1 mm, 3 µm) at 200 µL/min. Two gradient schemes were applied:
  
  • Basic/Neutral Analytes: Eluents of water/1% methanol/0.1% formic acid and pure methanol.
  • Acidic Analytes: Water with 2 mM ammonium acetate and methanol.
• Mass Spectrometry: TSQ Quantum Access triple quadrupole with electrospray ionization in positive mode for basic/neutral and negative mode for acidic compounds. Quantification via two specific MRM transitions plus retention time confirmation.

Used Instrumentation

• Thermo Scientific EQuan environmental quantitation system
• Thermo Scientific TSQ Quantum Access triple quadrupole mass spectrometer
• Hypersil GOLD Phenyl analytical and loading columns
• Autosampler with 1 mL sample loop and 6-way valve
• LC pumps delivering 1 mL/min (loading) and 200 µL/min (analytical) flows

Main Results and Discussion

• Calibration: Seven-point calibration over 5–150 ng/L (10–150 ng/L for some acids) showed excellent linearity (R² > 0.998).
• Limits of Quantitation: Achieved 5–10 ng/L depending on analyte.
• Method Segmentation: Four LC-MS segments accommodated multiple MRM transitions for basic analytes.
• Comparison to Offline Methods: Online SPE reduced sample prep time from 20 h (12 samples) to 1 h, and sample volume from 1 L to 10 mL, cutting shipping costs and simplifying logistics.

Benefits and Practical Applications

• High Throughput: Rapid automated preparation supports large-scale monitoring.
• Resource Efficiency: Low sample volume and solvent use decrease costs and environmental impact.
• Reliability: Automation reduces manual errors and increases reproducibility.
• Versatility: Applicable across basic, neutral and acidic pharmaceuticals in various water matrices.

Future Trends and Opportunities

• Method Expansion: Incorporate additional drug classes, personal care products and transformation products.
• High-Resolution MS: Enable suspect and non-target screening for broader water quality assessment.
• Field Deployable Systems: Portable LC-MS for on-site monitoring and rapid decision-making.
• Advanced Data Analytics: Machine learning and chemometric tools for trend detection and source attribution.
• Green Sample Prep: Development of more sustainable sorbents and solvent-free enrichment techniques.

Conclusion

The described online SPE-LC-MS/MS workflow using the EQuan system delivers a robust, sensitive and efficient approach to quantify 29 pharmaceuticals and metabolites in drinking water. Significant reductions in sample volume and preparation time, combined with high analytical performance, support routine monitoring and regulatory compliance in water quality management.

References

• Salomon M. (2007) Pharmaceutical active ingredients and environmental protection. UWSF-Z Umweltchem Ökotox 19(3):155-167.
• Current study: Consumption quantities of veterinary pharmaceuticals. UBA symposium, Pharmaceuticals in the environment, Berlin, 29-30 September 2004.