A new, simple and rapid HPLC method for determination of chlortetracycline in pig solid manure

Chlortetracycline (CTC) is the most frequently used antibacterial in todayʹs swine production for disease treatment and growth promotion. It is not absorbed completely and a considerable amount is excreted into manure when CTC is administrated to animal. For this reason there is high concern on potential risks that manure-derived CTC enters into the surface water and selects for resistant microorganism. In order to support the monitoring of CTC and study its fate in manure and environment, a simple and rapid analytical procedure was developed to determine chlortetracycline (CTC) in pig solid manure. The extraction solution, composed of acetone-4mol.L-1 hydrochloric acid-water (13:1:6, v/v/v), was mixed into the manure sample, and the solution was pH adjusted at 2.0-2.2 before extraction for 20 min. Chromatographic separation was carried out on a C18 column at 375 nm with UV detector, using isocratic elution with oxalic acid-methanol-acetonitrile (72:14:14), v/v/v) as mobile phase at room temperature. Recoveries of CTC spiked samples at the levels of 1.0 mg.kg-1, 2.0 mg.kg-1 and 10.0 mg.kg-1 were 92.2%-100.73% with relative standard deviation (RSD) of 2.81-7.11% intra-day and 1.343.25% inter-day, respectively. The limit of detection (LOD) and the limit of quantitation (LOQ) were 0.2 mg.kg-1 and 0.8 mg.kg-1, respectively. The procedure developed in this study was tested to be simple, sensitive and suitable for the determination and screening of CTC in pig solid manure samples.