Separation/Preconcentration Of Sulfonamides In Environment By Polypropylene Glycol-Based Aqueous Two-Phase Systems

Sulfonamides (SAs) are employed in both human and veterinary medicine as preventive and therapeutic agents for bacterial infective diseases. After normal applications, SAs can be excreted from human body or animal organisms through urine and feces. Ultimately these residues can find their way into the water environment. Rencently, the contaminations of sulfonamides in water environment and their potential ecological risks have drawn the domestic and oversea increasing concerns. Therefore, it is necessary to develop an effective and fast method to separation/preconcentration of trace sulfonamides in water environment. A new type of aqueous two-phase systems of polypropylene glycol (PPG)-salt was proposed, and the salting-out abilities of salts were discussed, which established the foundation for further theoretically analyze and apply this system. It is for the first time that based on PPG-based aqueous two-phase extraction with fluorescence spectrometry or high performance liquid chromatography to successful separation/preconcentration of trace sulfonamides in water environment. The main research contents and conclusion are as follows:(1) Experimental binodal curves were obtained for the PPG400+ inorganic salt (K3PO4/K2CO3/K2HPO4)+H2O systems at T=298.15 K. The optimum equation suitable to correlate the binodal data of the PPG4oo-inorganic salt aqueous two phase systems was obtained. On the basis of statistical geometry methods, the salting-out abilities of salt in forming aqueous two-phase systems with PPG400 were obtained by calculating the effective excluded volume, and the salting-out ability of inorganic salt follows the order of K3PO4>K2HPO4>K2CO3. Moreover, the Setschenow-type equation, Othmer-Tobias and Bancroft equations have been successfully used to correlate the tie-line compositions. Finally, the plaint points were also obtained for the studied systems.(2) Experimental liquid-liquid equilibrium for the PPG400+ organic salt (K3C6H5O7/K2C4H4O6/K2C2O4)+H2O systems have been determined experimentally at T=(298.15,308.15, and 318.15) K. The optimum equation suitable to correlate the binodal data of the PPG4oo-biodegradable salt aqueous two phase systems was obtained. Moreover, the salting-out abilities of biodegradable salt in forming aqueous two-phase systems with PPG400 were obtained by calculating the effective excluded volume, and the salting-out ability of salt follows the order of K3C6H5O7>K2C4H4O6≈K2C2O4.The effects of temperature on the binodal curves were studied, and it was observed that an increase of the temperature generally led to an increase of the biphasic area. Finally, The Othmer-Tobias and Bancroft equations have been successfully used to correlate the tie-line compositions.(3) The aqueous two phase system consisting of PPG4oo and NaH2PO4 coupled with molecular fluorescence spectrophotometry was developed for the separation and determination of trace sulfamethazine in real water samles. The effects of the amount of salt, pH, centrifugation time, and the temperature were investigated in details, and the optimal conditions for aqueous two-phase extraction were obtained. It has been observed that salting-out ability of salt and hydrophobic interaction play an important role in the extraction process. Under the optimal conditions, recoveries and relative standard deviations (RSD) at 10.0 and 20.0μg·L-1 spiking levels were 93.2-97.7% and 1.5-3.8% for real water samples.(4) The PPG400-based aqueous two-phase extraction coupled with high performance liquid chromatography (HPLC) was proposed for the separation and determination of sulfamethoxazole (SMX) in real water samples. The extraction yield of SMX in PPG400-salt ATPS is influenced by various factors, including the salt species, the amount of salt, pH, and the temperature. The mechanisms of phase behaviour and extraction were also discussed. Under the optimal conditions, the amouts of sulfamethoxazole in Yangzi River, Yudai Lake, tap water, and fish farm water samples were determined, recoveries and relative standard deviations (RSD) at 5.0 and 10.0μg·L-1spiking levels were 96.0-100.6 %and1.0-2.4% for real water samples.The research results indicate that PPG-based aqueous two-phase system is an effective method for separation/preconcentration of trace sulfonamides in real water samples.