A new preconcentration/separation method of [Bmim]BF4-( NH4)(2)SO4 aqueous two-phase solvent sublation was established and used to analyze tetracycline antibiotics, including tetracycline (TC) and oxytetracycline (OTC). The optimal conditions were investigated and discussed. The real water samples containing TC/OTC were analyzed, and the results were satisfying. The detection limits (LOD) of TC and OTC are 41.7 mu g L-1 and 52.1 mu g L-1, respectively. The relative standard deviation of 0.04 mg mL(-1) TC/OTC for 10 parallel determinations is less than 2.5%. Molar absorptivities (epsilon) of TC and OTC are 1.65 x 10(4) L mol(-1) cm(-1) and 1.3 x 10(4) L mol(-1) cm(-1), respectively. [Bmim]BF4-(NH4)(2)SO4 aqueous two-phase solvent sublation is shown to be promising for the separation and enrichment of trace TC/OTC as well as other substances in the environment. (C) 2010 Elsevier B.V. All rights reserved.