Catalytic effect of buffers on the degradation of doripenem in aqueous solutions

The catalytic effect of buffers (phosphate, acetate, borate, carbonate) on the degradation of doripenem in aqueous solutions was studied at 313 K in the pH range 0.82–11.56 (μ = 0.50 mol L−1) by an HPLC-UV method developed for kinetic studies of doripenem. It was observed that general acid–base catalysis occurred in all buffers and so catalytic rate constants were calculated. Specific acid–base catalysis of doripenem involved degradation of protonated molecules and zwitter ions of doripenem catalyzed by hydrogen ions, spontaneous degradation of zwitter ions under the influence of water and degradation of zwitter ions and monoanions catalyzed by hydroxide ions.