Application of ATPSs Based on Thermosensitive Copolymer in Partitioning and Determination of Ciprofloxacin in a Milk Sample

Phase behavior of copolymer-salt aqueous two-phase systems contaning PEG-PPG copolymer (L35 Pluronic) (Mw=1900) and five salts (potassium diphosphate, magnesium sulfate, potassium citrate, disodium tartrate and monosodium phosphate) have been studied. The results showed that the type of salt had a significant effect on the two-phase region. Ciprofloxacin, the most widely used antibiotic in the world, was selected as the target drug and its partition coefficient was determined in each aqueous two-phase system. The effect of copolymer concentration (at fixed salt concentration) on the partitioning of ciprofloxacin was studied. Based on the results, increasing the copolymer concentration leads to an enhancement in the partition coefficient of ciprofloxacin. Also, extraction efficiency reached 92.57 in ATPS composed of Pluronic L35 40% (w/w) and potassium diphosphate 10% (w/w). The influence of temperature on the partition coefficient of ciprofloxacin in Pluronic L35 - potassium diphosphate ATPS, was studied at four different temperatures (10, 15, 25 and 30 ). It was observed that at higher temperature, higher concentration of ciprofloxacin was measured in the top phase (higher partition coefficient). Standard thermodynamic properties were determined and showed that the partitioning of ciprofloxacin to the top phase is a spontaneous, endothermic and entropy-driven process. The amount of ciprofloxacin was determined in a real sample (milk) using an aqueous two-phase system containing 35% w/w Pluronic L35 and 10% w/w dipotassium phosphate at (25±1) . The amount of partition coefficient of ciprofloxacin in this system was 5.51 and the recovery factor of this drug in the ATPS is 85.08%.