青霉素G 钾盐水溶液极不稳定,其β-内酰胺环极易水解,使失去生物活性。我们用化学动力学方法预测了本品pH 4溶液在室温(25℃)时能保持90%效价的时间t_(0.9)口和半衰期t_(0.5)。实验方法青霉素G 钾盐水溶液的加速实验:称取青霉素G 钾70～80mg,于100ml 干燥容量瓶中,加pH4的枸橼酸-磷酸氢二钠缓冲液(按中国药典1977年版附录128页配制)使溶,并稀释至刻度摇匀。立即用5ml 移液管吸取溶液二份,每份5ml。将容量瓶 Penicillin G potassium salt aqueous solution is very unstable, its β-lactam ring is very easy to hydrolyze, loss of biological activity. Using chemical kinetics, we predicted the time t_ (0.9) and the half-life t_ (0.5) of the pH 4 solution at 90% potency at room temperature (25 ℃). Experimental methods Accelerated experiments of penicillin G potassium salt solution: Weigh penicillin G potassium 70 ~ 80mg, in 100ml dry volumetric flask, add citric acid - disodium hydrogen phosphate buffer pH4 (according to the Chinese Pharmacopoeia 1977 edition Appendix 128 ) To dissolve, and dilute to the mark to shake. Immediately pipette the solution in duplicate with 5 ml pipette, 5 ml each. The volumetric flask