Stability Study Of Chloramphenicol In Polyoxy-ethylated Nonionic Surfactant-Water System

The chloramphenicol eye drops are widely used and have a broad market prospect. However, the chloramphenicol is unstable and hydrolyzes easily in aqueous solution. It is of great importance to improve the stability of chloramphenicol in aqueous solution.The Gaussian was used for the geometric configuration optimization and charge distribution analysis of chloramphenicol. The reason that the chloramphenicol hydrolyzes easily was got. The hydrolysis kinetics of chloramphenicol was discussed and the hydrolytic kinetic equation was abtained. It was found that the rate of hydrolysis was twice with 7℃increasing of the temperature, which indicated the hydrolysis was sensitive with temperature.'H-NMR was used to study the solubilization position of chloramphenicol in the polyoxyethylated nonionic surfactant micelle and the exiting forms of small amount of water in the surfactant. The chloramphenicol was orientation arranged in the surfactant micelle. The hydrophobic group of chloramphenicol was solubilized in the palisade layer of the micelle while the hydrophilic group in the hydrophilic shells which were composed of many oxyethylene groups. The reverse micelle formed in Tween-80 and AEO-10 systems respectively with 2.8 percent of water in mass fraction, but did not in the TX-13 and EL-10 systems with the addition of water.The stability of chloramphenicol was studied in different polyoxyethylated nonionic surfactant-water systems. The chloramphenicol partitioned between the aqueous phase and the micellar phase. The hydrolysis behavior of chloramphenicol in the aquous phase was studied by hydrolyzing in buffer solution, while in the micellar phase was studied by hydrolyzing in the system composed of surfactant and small amount of water. The results indicated that polyoxyethylated nonionic surfactants played stabilization effect on chloramphenicol. The hydrolysis rate constant in micellar phase was only 1/10-1/50 of that in the aqueous phase. It was this reason that the stability of chloramphenicol increased.The structure-activity relationship between the polyoxyethylated nonionic surfactant and chloramphenicol was discussed. The degree of polymerization of ethylene oxide had slight effect on the stabilization of chloramphenicol while the structure of hydrophobic group had significant effect. The polyoxyethylated nonionic surfactant with long side chains, such as Tween-80 and EL, had better effect on the stabilization of chloramphenicol.