Determination of Antibiotic Metabolites in Soils and Sewage

In a recent study published in Analytical and Bioanalytical Chemistry, researchers proposed a new method for the determination of antibiotics and eight different metabolites, using techniques like ultrasound-assisted extraction and liquid chromatography–tandem mass spectrometry (LC–MS/MS) (1).

After antibiotics are given to a patient, they are excreted from the body as parent compounds and metabolites. This means that these substances can enter the environment as effluents or sewage sludge from wastewater treatment plants (WWTP). In 2020, the World Health Organization (WHO) warned that antibiotic resistance is increasing, making many diseases harder to treat.

In this study, the researchers developed a method for routine control of multiclass high-concern antibiotics and their main metabolites. The method was based on three different techniques: ultrasound-assisted extraction, dispersive solid-phase extraction clean-up, and analytical determination by LC–MS/MS. Extraction solvent volume, extraction time, and the number of extraction cycles affecting each stage of the method were optimized via a Box–Behnken design. The method was used on different treatment stages of sewage sludge including non-treated sludge: primary and secondary sludge; and treated sludge: digested sludge and compost and to agricultural soil.

Following the experiment, most of the compounds displayed limits of quantification in the range of 0.03–7.50 ng g−1 dry weight (dw). Accuracy values ranged from 70–102%, while precision remained below 17%. Macrolides and fluoroquinolones held the highest concentrations. The lowest antibiotic concentrations were measured in both compost (highest concentration: 27 ng g−1 dw, corresponding to norfloxacin) and soil samples (highest concentration: 93 ng g−1 dw, corresponding to a metabolite of clarithromycin).

The scientists claim this method as the first to be developed for the determination of multiclass antibiotics and their main metabolites in sludge from different treatment stages. Furthermore, it can prove useful in obtaining antibiotic information prior to sewage sludge being applied to agricultural soils, as well as those within agricultural soils.

References

Mejías, C.; Santos, J. L.; Martín, J.; Aparicio, I.; Alonso, E. Multiresidue method for the determination of critically and highly important classes of antibiotics and their metabolites in agricultural soils and sewage sludge. Anal. Bioanal. Chem. 2023. DOI: https://doi.org/10.1007/s00216-023-04982-3