Quantitative Determination of Fluoroquinolone Residues in Environmental Waters Sourced Near European Aquacultures Using Automated Solid-Phase Extraction

International Journal of Chemistry | Vol. 17, No. 8, August 2026 | pp. 89–96

DOI: 10.46882/2026/IJC/000218

Article Type: Original Research Paper

Title: Quantitative Determination of Fluoroquinolone Residues in Environmental Waters Sourced Near European Aquacultures Using Automated Solid-Phase Extraction

Names of Authors: J. M. S. Cardoso¹, E. R. Watson²*

Authors’ Affiliations:
¹Department of Pharmacy, University of Coimbra, Coimbra, Portugal.
²Department of Chemistry, University of Cambridge, Cambridge, United Kingdom [American Expatriate Fellow].

Abstract: The persistent release of veterinary antibiotics from intensive aquaculture facilities into surrounding aquatic networks introduces significant environmental hazards, including the potential development of multi-drug resistant bacterial strains. This study describes the optimization and validation of a highly sensitive and rapid method combining automated online solid-phase extraction (SPE) with ultra-high-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) for the simultaneous quantification of four regulated fluoroquinolones (ciprofloxacin, enrofloxacin, norfloxacin, and ofloxacin) in environmental surface waters. Chromatographic separation was achieved within 6.0 minutes using a reversed-phase C18 stationary column and an acidified water-acetonitrile gradient mobile phase at a constant flow rate of 0.4 mL/min. Multiple reaction monitoring (MRM) mode was utilized for detection under positive electrospray ionization parameters. Method validation followed the international ICH guidelines. Excellent linearity was established over a concentration range of 1.0 to 100.0 ng/L, yielding high correlation coefficients (R²) exceeding 0.999. The limits of detection (LOD) ranged between 0.15 and 0.42 ng/L across all compounds. The practical utility of the sensor array was demonstrated by screening real water profiles collected adjacent to commercial marine arrays, revealing trace enrofloxacin concentrations up to 45.8 ng/L, confirming the method's high performance for water quality monitoring.

Keywords: Fluoroquinolones; Solid-phase extraction; Tandem mass spectrometry; Aquaculture effluents; Water pollution; Method validation

Manuscript Timeline: Received: March 02, 2025; Revised: May 12, 2025; Accepted: June 20, 2025; Published: August 19, 2026.

Citation: Cardoso, J. M. S., & Watson, E. R. (2026). Quantitative Determination of Fluoroquinolone Residues in Environmental Waters Sourced Near European Aquacultures Using Automated Solid-Phase Extraction. International Journal of Chemistry, 17(8), 89–96.

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