| Accumulation and elimination of semicarbazide（SEM） in channel catfish（Ietalurus Punetaus） tissue and pond under practical farming laboratory conditions were studied. We took the method of splashing nitrofurazone in whole pond, and the same sizes of channel catfish（124.13±25.2）g were exposed to freshwater containing semicarbazide for one year at natural conditions. The concentrations of SEM in environmental（water, mud） and tissue（muscle, skin） samples was determined by liquid chromatography tandem mass spectrometric（HPLC-ESI/MS/MS）. The results showed that semicarbazide concentration in water and tissue decreased quickly in the beginning, then the elimination trends started to level off and maintained a certain concentration fraction in certain period, but the semicarbazide concentration in mud presents downtrend in the overall period without a linear progression. The SEM in skin was enriched in the first five days, then the content of SEM represents decreased linearly over time. The elimination half-life of SEM in water, muscle and skin were 1.7 d, 2.09 d and 2.42 d, respectively. Semicarbazide concentrations in channel catfish and water were below 0.5 μg·kg-1 at the end of the experiment except mud. The concentration in the channel catfish and the environment present significant correlation（P<0.01）, but the SEM was not enriched obviously in the tissues of channel catfish. |
