Extraction of antibiotics using aqueous two-phase systems based on ethyl lactate and thiosulphate salts

Ethyl lactate is a hydrophilic solvent produced from bio-renewable sources (bioethanol and lactic acid produced from corn fermentation) that is considered as a “green” solvent due to its extremely low toxicity, biodegradability and negligible eco-toxicity. This work focuses on the utilization of ethyl lactate to form aqueous two-phase systems (ATPS) in the presence of inorganic salts for the extraction of antibiotics from aqueous solutions. The performance of three thiosulfate salts (Na2S2O3, K2S2O3 and (NH4)2S2O3) as salting-out media for the extraction of chloramphenicol and tetracycline from their aqueous solutions was examined. In this respect, cloud points for the ternary solutions composed of ethyl lactate, water and salt were determined at atmospheric pressure (0.1 MPa) and 298.2 K. Partition coefficients of chloramphenicol and tetracycline between the two phases were determined by chemical analysis of phases in equilibrium for different initial compositions at 298.2 K. This paper is the first report to demonstrate the ability of the ATPS based on ethyl lactate to efficiently separate antibiotics. Thus, ATPS based on ethyl lactate represents a new and green platform for the extraction of antibiotics from aqueous solutions which can facilitate their detection, identification and quantification in surface waters as well as their extraction from fermentation broths.