Identifying the impact of a pandemic on pharmaceutical river contamination by LC-MS/MS

Importance of the Topic

The COVID-19 pandemic has altered prescription trends and healthcare practices worldwide, raising concerns about how these changes affect pharmaceutical residues in surface waters. Monitoring river contamination provides valuable insight into public health impact and environmental risk, enabling authorities to assess treatment efficacy and potential ecological effects.

Objectives and Study Overview

This study compared pharmaceutical loads in River Thames samples collected before (late 2019) and during (late 2020) the pandemic. By integrating targeted and non-targeted LC-MS/MS workflows, the research aimed to identify shifts in compound occurrence and concentration linked to changes in medication use or wastewater discharge patterns.

Methodology and Instrumentation

• Sampling and Preparation: Filtered (0.2 µm PTFE) river water samples from 2019 (n = 8) and 2020 (n = 12) were directly injected (10 µL) into LC-MS/MS systems.
• Liquid Chromatography: Shimadzu Nexera system with biphenyl column (100 × 2.1 mm, 2.7 µm), binary gradient of water/methanol +2 mM ammonium formate and 0.002% formic acid, flow rate 0.4 mL/min.
• Mass Spectrometry:
  
  • Targeted MRM on Shimadzu LCMS-8060 triple quadrupole.
  • High-resolution analysis on Shimadzu LCMS-9030 QTOF with TOF survey (m/z 100–920, 100 ms) and DIA-MS/MS scans (m/z 40–920, 25 ms, variable isolation width).
• Data Processing: LabSolutions Insight for targeted and non-targeted screening; component detection algorithm with suspect list (>1 000 compounds) using ±5 ppm mass extraction.
• Compound Identification: Product-ion matching against multiple MS/MS databases— in-house Shimadzu Toxicology DB, Wiley MS for ID, HighResNPS, MassBank and other public libraries—applying mass accuracy, isotopic scoring, and retention time criteria for confident reporting.

Main Results and Discussion

• Detection Panel: Twenty-one pharmaceuticals were found in >20% of samples (peak height >1000, S/N>3).
• Year-on-Year Changes: Marginal increases in 2020 vs. 2019 for diclofenac, carbamazepine, venlafaxine and gabapentin (all <100 ng/L).
• Highest Relative Increases: Sulfapyridine, ketamine and metformin showed the most pronounced rise, likely reflecting altered prescription patterns or wastewater inputs during lockdown.
• Decreases: Lidocaine levels were lower in 2020 compared to 2019.
• Method Agreement: Targeted MRM and high-resolution QTOF results correlated well (slope = 0.8, R²≥0.95).
• Analytical Confidence: DIA-MS/MS spectral matching reduced false positives/negatives; multiple libraries provided complementary evidence across different instruments.

Contributions and Practical Applications

• Demonstrated an integrated workflow combining targeted and non-targeted LC-MS/MS for environmental monitoring of pandemic-related pharmaceutical contamination.
• Offered a robust protocol for routine QA/QC in water quality laboratories and epidemiological surveillance via wastewater-based epidemiology.
• Showcased the benefit of high-confidence compound identification using orthogonal MS/MS libraries and matched retention time criteria.

Future Trends and Potential Applications

• Expansion of suspect/non-targeted screening using larger, curated spectral libraries and advanced data-mining algorithms.
• Incorporation of machine learning for automated peak picking, feature prioritization and structure elucidation in complex environmental matrices.
• Development of in situ or near-real-time monitoring technologies leveraging miniaturized MS or sensor arrays.
• Global harmonization of MS/MS databases and data sharing platforms to support cross-regional environmental surveillance.

Conclusion

This study illustrates that pandemic-driven shifts in prescription and wastewater discharge can be detected at trace levels in river water. The combined targeted and high-resolution LC-MS/MS approach delivers reliable quantification and confident compound identification, supporting environmental risk assessment and public health monitoring.