Stability of penicillin G in ionic liquid [Bmim]PF6

The extraction of penicillin G by ionic liquid [Bmim]PF6 has exhibited promising prospect. The stability of penicillin G is crucial for developing a green ionic liquid-based extraction technology. In this work, the stability of penicillin G in [Bmim]PF6 was systematically investigated. The results showed the stability of penicillin G was significantly influenced by pH and temperature. It tended to be more stable when pH value increased from 1.5 to 4.0 and the temperature gradually decreased. The half-life (t1/2) of penicillin G in [Bmim]PF6 was 17.7 h in the optimal technological condition (pH 2.0 and 10 °C), which is enough for the requirement of extraction technology. The reaction of penicillin G in [Bmim]PF6 followed the first order kinetics in the pH range 2.0-4.0. Three isomers of penicillin G were found through rearrangement at pH 2.0, and their structures were not affected by temperature.