Determination of Sulfonamide Antibiotics in Wastewater by Liquid Chromatography– Tandem Mass Spectrometry

Importance of the Topic

Waterborne antibiotic residues pose risks of bacterial resistance and ecological harm. Sulfonamides are widely applied in human and veterinary medicine and can pass through wastewater treatment systems. Sensitive methods are required for monitoring trace levels of these emerging contaminants.

Aims and Overview

This study aimed to develop and validate an analytical protocol for quantifying trace sulfonamide antibiotics in secondary effluent samples. The approach combines solid phase extraction with liquid chromatography tandem mass spectrometry to achieve low part per trillion detection.

Methodology

Sample Preparation:

• Collection of secondary effluent from sewage plants followed by vacuum filtration
• Dilution of 50 mL samples with deionized water and acidification to pH 4
• Addition of deuterated sulfamethoxazole internal standard prior to enrichment
• SPE enrichment using cartridges at 5 mL/min flow, washing with water and elution with methanol
• Evaporation under nitrogen and reconstitution in 0.5 mL mobile phase A (0.1% formic acid in water)

Chromatography and Detection:

• HPLC on a C18 column (150×2.1 mm, 3.5 µm) with gradient of 0.1% formic acid in water (A) and acetonitrile (B) at 0.2 mL/min
• MS/MS analysis on a TSQ Quantum Ultra triple quadrupole with positive electrospray ionization and SRM monitoring
• Use of two diagnostic transitions per compound and 1/x weighted calibration over 0.1–100 µg/L

Instrumentation

• Surveyor HPLC System
• TSQ Quantum Ultra Triple Quadrupole Mass Spectrometer

Main Results and Discussion

Calibration exhibited excellent linearity (r2>0.997) across the target range. Limits of detection were approximately 0.05 µg/L. Recoveries ranged from 72% to 120% with inter-day RSDs below 20%. Sulfamethoxazole was detected in all wastewater effluents at a median concentration of 150 ng/L, demonstrating incomplete removal during treatment.

Benefits and Practical Applications

• Enables reliable measurement of ng/L concentrations of sulfonamides in complex matrices
• Supports environmental monitoring and risk assessment of antibiotic pollution
• Facilitates evaluation of wastewater treatment efficiency

Future Trends and Opportunities

• Integration with high resolution mass spectrometry for broader screening of pharmaceuticals
• Automation of sample preparation to increase throughput
• Extension to additional antibiotic classes and transformation products
• Incorporation into regulatory monitoring frameworks

Conclusion

The described LC-ESI-MS/MS method provides a sensitive, accurate, and reproducible tool for detecting sulfonamide residues in wastewater effluents. Its high recovery and low detection limits support environmental surveillance and contribute to understanding antibiotic fate in aquatic systems.

References

1. Petrovic M Hernando MD Diaz-Cruz MS Barcelo D J Chrom A 2005 1067 1-14
2. Gobel A McArdell CS Suter MJ-F Giger W Anal Chem 2004 76 4756-4764
3. Yang S Cha K Carlson K Rapid Commun Mass Spectrom 2004 18 2131-2145