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The property, function and residual of chloramphenicol were revived in this paper. The advantages and disadvantages of the current domestic and international methods for the determination of the trace CAP were summarized. Aimimg on the common problems of the current determination of the trace antibiotic, this study, which combines small molecule aqueous two-phase with solvent flotation for the first time, proposed a rapid, simple, low cost, non-toxic, pollution-free method for the determination of the trace CAP in wastewater and discussed the mechanism of this method.In order to get better effect, this paper studied small molecule organic solvent and inorganic salts the abilities for phase separation; the partition of CAP in the small molecule aqueous two-phase; and tries to apply selected C2H5OH/K2HPO4 aqueous two-phase for extraction, separation and concentration of the trace CAP in environment, optimizing the extraction conditions. Meanwhile aiming on the small molecule flotation, the factors on the flotation efficiency and enrichment coefficient such as the percentage of inorganic salts, the volume of organic solvent, solution pH, nitrogen flow rate, aeration time were discussed in details.Through experimental research, a new method preliminary to determine small molecule organic solvents and inorganic salts the abilities for phase separation:△p criterion method, was established. Based on△p criterion method, the abilities of the inorganic salts and organic solvents for phase separation followed the order of (NH4)2SO4>K2HPO4>KOH,CH3CH2OH>CH3COCH3>CH3CH2CH2OH. According to the mechanism of aqueous two-phase flotation and the characterizes of the flotation devices, we proposed flotation required three aqueous two-phase system conditions, combined with the partition of CAP in the small molecule aqueous two-phase, CH3CH2OH/K2HPO4 aqueous two-phase system was chosen in the following extraction and flotation experiment. The results showed that when the total volume was 10ml, the optimal the extraction conditions of CAP were:the volume of CH3CH2OH was 3ml, the mass of K2HPO4 was 5g, pH controlled at around 10.3. Under the optional conditions, the extraction efficiency of CAP was up to 95.5%, the concentration coefficient was up to 2.7. In 50ml homemade flotation cell, when the mass concentration of K2HPO4 was 45%, the volume of CH3CH2OH was 5ml, the nitrogen flow rate was 2.5ml/min, and the flotation time was 50 min, the concentration coefficient of CAP was up to 15.06; the sublation efficiency was up to 96.5%.The linear range was 7～100μg/ml; the limit of detection was 2.75ng/ml. It has been applied to the detection of river water and ponds samples, these samples confirmed as having no detectable CAP. The relative recovery was 89.44～101.2%, the relative standard deviation was 1.1～2.2%. The reproducibility of result was good. Thus, the method could apply to separation, concentration and determination of trace CAP in wastewater.
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