Degradation of oxytetracycline in seawater at two different temperatures and light intensities, and the persistence of oxytetracycline in the sediment from a fish farm

Abstract

A rapid procedure for the quantitative determination of the antibiotic oxytetracycline in sediments and in seawater using high performance liquid chromatography is presented. The mean recoveries from the sediment and from seawater were 98.4% and 99.5%, respectively. The limit of detection was 0.1 ppm for sediment and 0.01 ppm for seawater when injecting 150 μgl of sample. The persistence of oxytetracycline in the sediment was highly dependent on the rate of sedimentation. Based on measurements during the first 12 weeks and with a very small sedimentation rate, the half-life ( t 1 2 ) of the antibiotic was 32 days. When the oxytetracycline layer was immediately covered with an additional 4 cm of sediment, the degradation was much slower ( t 1 2 =64 days ). The degradation of oxytetracycline in seawater was rapid. The half-lives were 128 and 168 h at 5 and 15°C, respectively, under illumination for 24 h a day with a 40-W fluorescent tube, and 390 and 234 h, respectively, in aquaria maintained in darkness.