The Kinetics of Oxytetracycline Degradation in Deionized Water under Varying Temperature, pH, Light, Substrate, and Organic Matter

Abstract

The kinetics of oxytetracycline (OTC) degradation in deionized water was studied under the influence of various environmental factors. The experiment was conducted with a solution of 10 g aqueous OTC /mL in 600-mL glass beakers under controlled laboratory conditions. The aqueous concentration of OTC was determined by high-performance liquid chromatography. Low temperatures (4ЊC) favored high drug stability, and high temperatures (43ЊC) speeded OTC degradation, resulting in a very short half-life of 0.26 Ϯ 0.11 d. Light exposure caused photodecomposition, reflecting degradation rates threefold higher than those under dark conditions. Acidic conditions (pH 3.0) favored drug stability (half-life ϭ 46.36 Ϯ 4.92 d), and alkaline conditions (pH 10.0) increased the degradation rate (half-life ϭ 9.08 Ϯ 4.22 d). The presence of a substrate (bentonite clay) resulted in an approximate 17% decrease in OTC concentration within 5 min of contact. Addition of organic matter (fish feed) along with the substrate resulted in a 41% decrease in OTC concentrations within 5 min of contact.

Oxytetracycline sorption onto Iraqi montmorillonite

“…2). The rate of decrease was small in comparison with the reports of Doi and Stoskopf (2000) and Kulshrestha et al (2004), who showed that adsorption decreased rapidly over this pH range and reported a strong correlation between pH and the sorption capacity of TC. Adsorption increased slightly at pH 10.…”

“…This can be related to the higher concentration of negative surface charges of clay particles in the alkaline medium. The decrease in efficiency may be related to the possible degradation of the drug in alkaline medium (Doi and Stoskopf 2000). However, similar pH-dependent adsorption trend is absent in low OTC concentrations (0.20, 0.36 mmol L -1 ).…”

“…The majority of OTC adsorption took place within the first 2 h. Beyond 2 h, increase in adsorption was relatively slow. Doi and Stoskopf (2000) reported that the presence of a bentonite clay surface resulted in an approximate 17 % decrease in OTC concentration within 5 min of contact. First-order kinetic model was applied to assess the sorption process but the correlation of the data was weak.…”

Toxicidade aguda e risco ambiental do antibiótico oxitetraciclina para tilápia ( Oreochromis niloticus ), Daphnia magna e Lemna minor

“…After the period of exposure to OTC, according to Doi and Stoskopf (2000), this antibiotic hardly degrades in water under the conditions of this study.…”

Antibiotic residues and resistance in the environment

“…Tetracyclines are stable in acid media, but not in alkaline conditions, and form salts in both conditions (Doi, 2000;Halling-Sørensen, 2002). Their water solubility ranges between 230 and 5200 (mg L…”