1992 年 40 巻 8 号 p. 2044-2048
The catalytic effect of various buffer systems (citrates, acetates, phosphates, borates and carbonates) on the degradation of SCH 29482 and FCE 22101 in aqueous solution was studied at 35°C and a constant ionic strength of 0.5 mol·dm-3 over a pH range of 3.50 to 10.0. The observed degradation rates, obtained by measuring the remaining intact antibiotic, were shown to follow pseudo-first-order kinetics with regard to antibiotic concentrations and to be significantly influenced by general acid and general base catalysis. The changes in the concentration of intact SCH 29482 in the solutions were established by spectrophotometric determination of the reaction product with imidazole, while those of intact FCE 22101 were determined by reverse-phase high performance liquid chromatography with ultraviolet-detection. Of the buffer systems employed in the kinetic studies the borate one had the greatest catalytic effect. The pH-rate profiles for SCH 29482 and FCE 22101 showed a degradation minimum at pH 5.86 and 5.22, respectively. The SCH 29482 is more reactive with hydrogen ion than the FCE 22101 and less reactive with hydroxide ion. The Arrhenius activation energies were determined for SCH 29482 and FCE 22101 at pHs 4.23, 6.59 and 8.60.
