Method optimization for determination of tetracyclines insoils and compost and their degradation in soils

Based on method improvement and optimization for determination of Oxytetracycline (OTC), Tetracycline (TC) and Chlortetracycline (CTC) using highperformance liquid chromatography (HPLC) and the extraction method of tetracyclines (TCs) in soils and compost, the degradation of these three TCs in soils was studied. The results indicated that these three TCs could be completely eluted to baseline separation in 20 min by a column of Agilent Eclipse XDB-C8 (4.6150 mm, 5 m). The mobile phase was 0.01 mol/L oxalic acidACNMeOH (79/10.5/10.5, v/v/v) at a flow rate of 10 mL/min. The injection volume of sample solution was 5 L and the UV detector wavelength was at 268 nm. A significant linear correlation between these TCs under the concentration of 0-10 mg/L was observed (r 0.999). The TCs in soils and compost could be extracted by a mixture solution of 1 mol/L NaCl/0.5 mol/L oxalic acid/ ethanol (25/25/50, v/v/v), with the recoveries ranged from 76.0% to 92.5%. After 49 d of incubation at 25 oC in the dark condition, the degradation rates of the TCs in loam soil and red clay were 67%-72% and 36%-46%, respectively. The corresponding halflife of TCs was 26-30 d in loam soil and 46-75 d in red clay, respectively, indicating that the degradation of TCs in the loam soil was significantly faster than that in the red clay. Moreover, there was no significant difference between the halflife of TCs in the loam soil, while the degradation rates of CTC and TC in the red clay were significantly higher than that of OTC.