Tetracycline Speciation Study in Aqueous Medium

Tetracycline is a broad-spectrum antibiotic considered an emerging contaminant with major effects on human health and the ecosystems. Using the techniques of UV absorption spectroscopy and capillary zone electrophoresis, the characterization of tetracycline in aqueous medium is presented. Likewise, four acidity 4+ constants were determined: pKa1 = 3 = (3.277 f 0.067), pKa2 = 2- 3 = (7.397 f 0.055), 2- pKa3 = 2- = (9.349 f 0.039) and pKa4 = 3- 2- = (11.278 f 0.024). Finally, capillary zone electrophoresis corroborates the predominance of five tetracycline species (TcH4+, TcH3, TcH2-, TcH2- and Tc3-) and presents a proposal for the deprotonation mechanism for tetracycline in aqueous medium.