Penicillin. III. The Stability of Penicillin in Aqueous Solution

Abstract

The decomposition of crystalline penicillin in various buffer solutions from pH 2 to 11 at temps. from 0[degree] to 37[degree] C was studied. Although not stated in the original manuscript, it is now permissable to say that crystalline Penicillin G was used. The results are shown in a series of graphs. From them it appears that the destruction of penicillin in aqueous soln. is a first-order irreversible reaction. The opt. stability point for Penicillin G approaches pH 6 and above or below this point destruction is rapid, depending on pH and temp. E.g., the half-life (time in hrs. to destroy 50%) at 24[degree] C of a soln. containing 100-125 Oxford units per ml. is 0.283 at pH 2, 13.2 at 4, 356 at 6, 122.4 at 8, and 9.7 at 10. The time required to destroy a soln. of pure penicillin at pH 2 between [long dash]10[degree] and +44[degree] C and the rate of destruction at any chosen point during that time may be calculated by the use of formulae presented in the paper.