Adsorption characteristics of polythiophene for tetracyclines and determination of tetracyclines in fish and chicken manure by solid phase extraction-HPLC method

Porous polythiophene materials were successfully synthesized by external-crosslinker method and applied as sorbents in solid-phase extraction. A method for the determination of tetracycline antibiotics (tetracycline/ oxytetracycline/doxycycline) in fish and chicken manure was proposed by combining solid phase extraction-ultraviolet visible spectrophotometer (SPE-UV) and solid phase extraction-high performance liquid chromatography (SPE-HPLC). The effects of material dosage, extraction time, washing time, eluent type and dosage, and the reusability of polythiophene sorbent on extraction rate were investigated. With the use of SPE-HPLC method, satisfied linearity for three tetracyclines antibiotics was obtained in the range of 0.004–1 mg/L. The detection limits (LODs) were ranged from 0.0012 to 0.0027 mg/L and the relative standard deviations (RSDs) were 3.5–7.3% (n = 5). The recoveries in actual fish samples and chicken manure samples were 91.1–114.1% and 69.5–93.2%, respectively. No tetracycline antibiotics were detected in fish samples and no doxycycline was detected in chicken manure samples. However, oxytetracycline and tetracycline were detected in two chicken manure samples with the contents of 5.12, 6.58 mg/kg and 6.08, 7.72 mg/kg, respectively. This method was simple, sensitive and suitable for the determination of tetracyclines in practical samples.