Effect of buffers on the ertapenem stability in aqueous solution
karbala journal of pharmaceutical sciences,
Volume 5, Issue 7, Pages 51-57
AbstractThe stability of ertapenem, the active principle of Invanz®, was investigated in citrate (pH 3.50), acetate (pH 4.00 and 5.00), phosphate (pH 5.50, 6.50 and 7.50) and carbonate (pH 8.50) buffer solution at 30˚C and at an ionic strength of 0.5mol L-1.
Changes in the concentration of ertapenem were determined by reverse-phase high performance liquid chromatography (HPLC) with UV-detection at 230 nm. The mobile phase used was phosphate buffer (20 mM) and acetonitrile (92.5:7.5) respectively.
The degradation of ertapenem obeyed pseudo first-order kinetics under all conditions employed in this study. The activation energy (Ea) for the degradation of ertapenem in hydrochloric acid (pH 1.20) was 62.7kJmol-1. The catalytic effect of acetate and phosphate buffer species towards the degradation of ertapenem was also investigated. The buffer species have a significant catalytic effect on ertapenem degradation which increased with increase of buffer concentration. pH-rate profile of ertapenem displayed three regions; an acid catalytic reaction below pH 5.00, a pH-independent region between pH 5.00 to 7.50 and base catalysed above pH 7.50.
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