RT Journal Article
T1 Analytical challenges and occurrence of antibiotics in biosolids from municipal sewage treatment plants in North Spain
A1 Barros Soto-Quiroga, Andrés
A1 Castro Varela, Gabriela
A1 Ramil Criado, María
A1 Rodríguez Pereiro, Isaac
K1 Liquid chromatography mass spectrometry
K1 Extraction strategies
K1 Clean-up
K1 Prioritized antibiotics
K1 Biosolids
K1 Mass Balance
AB Antibiotics are among the most concerning pharmaceutical contaminants released from municipal sewage treatment plants (STPs), occurring both in treated effluents and in dewatered biosolids. This study examines key analytical challenges during the determination of ten antibiotics in sewage wastes using liquid chromatography–tandem mass spectrometry (LC-MS/MS). Furthermore, results of their distribution in dewatered biosolids from different STPs are presented. Fluoroquinolones were identified as the most problematic compounds due to sorption on glassware, strong interaction with sample matrix, and signal suppression effects during LC-MS/MS analysis. Optimized extraction, based on sonication of freeze-dried samples with a buffered acetonitrile–water solution (pH 4.4, 1:1), yielded average recoveries between 74% and 108%, with moderate variability across sludge types. During simultaneous quantification of multiclass antibiotics, fluoroquinolones exhibited moderate to high signal attenuation depending on the matrix. For this group of compounds, signal suppression could be mitigated by fractionating extracts using mixed-mode (reversed phase and cation exchange) sorbents. Combined with isotopically labelled surrogate standards, solvent based calibration enabled accurate quantification of all targeted compounds, achieving limits of quantification below 5 ng g⁻¹. Azithromycin, clarithromycin, norfloxacin, ciprofloxacin and ofloxacin were ubiquitous in dewatered biosolids, with median concentrations ranging from 7 ng g-1 (clarithromycin) to 1761 ng g-1 (ofloxacin). A mass balance assessment of emissions through treated wastewater and biosolids highlighted azithromycin, ciprofloxacin, norfloxacin, and ofloxacin as the priority antibiotics for monitoring in final dewatered solid waste streams (biosolids) from STPs.
PB Elsevier
SN 0021-9673
YR 2026
FD 2026-04-24
LK https://hdl.handle.net/10347/47072
UL https://hdl.handle.net/10347/47072
LA eng
NO Barros, A., Castro, G., Ramil, M., & Rodríguez, I. (2026). Analytical challenges and occurrence of antibiotics in biosolids from municipal sewage treatment plants in North Spain. Journal of Chromatography A, 1778, 467015. 10.1016/j.chroma.2026.467015
NO We acknowledge the financial support received through SAFESLUDGE project, ref. PID2023-147051OB-I00, funded by Ministry of Science, Innovation and Universities & Estatal Agency of Research (MICIU/AEI/10.13039/501100011033); and the regional administration (Xunta de Galicia, project ED431C 2025/21). We also thank Agilent for providing free access to the LC-QqQ-MS equipment employed in this research.
DS Minerva
RD 22 may 2026