A Validated Analytical Approach for Antibiotic Residues Determination in Water Using NaOH-Modified Diatomaceous Earth as a Sustainable Sorbent

Antibiotics are among the most widely used classes of pharmaceuticals in modern medicine. Due to their frequent use, antibiotic residues have been detected in the environment, particularly in aquatic environments. In this study, HPLC method, with sample pretreatment was optimized and validated in order to analyze the presence of two commonly used antibiotics—cephalexin and tetracycline in water samples. Samples were collected from different sources, including wastewater, tap water, the Danube River and groundwater, in order to evaluate how the matrix affects the overall analysis. The main objective of this research was to develop an effective and reliable method for the detection of these antibiotic residues in water. A secondary aim was to establish the most effective sample preparation method. Samples were prepared using the dispersive solid-phase extraction (dSPE) technique with modified diatomaceous earth as the sorbent. The dSPE procedure was applied primarily for sample clean-up and reduction in matrix effects prior to HPLC-DAD analysis. The sorbents were characterized prior to use to investigate the influence of modification on their sorption properties.