In order to investigate the importance of chemical indicators (CI) in the confirmation of the reliability of sterilization process for pharmaceutical solutions which have different heat penetrations depending upon the container sizes or autoclaves, containers in 3 different capacities (0.5, 1, 3 liters) filled with purified water were autoclaved at 115° for 10 to 60 minutes. In the containers commercial CI's (products A, B and C) were immersed. Sensuous decision, color difference (ΔE) and LIF, which was found in our previous paper to be useful for the determination of sterilization time in large volume solutions, were evaluated.
Autoclaving time at which CI gives the confirmation evidence by sensuous decision was shortest when measured in chamber and the time required for products A and B was 15 minutes. Autoclaving time in solution was different among the products in the following order: C> A> B. But in all products the larger the capacity of containers becomes, the longer the time becomes. Linear relationship between ΔE of product A and of B and log of LIF was observed, even if the container size or autoclaving time is different.
LIF, therefore, can be estimated from ΔE. It is proved that when product A or B gives the confirmation evidence for sterilization to solution by sensuous decision, its solution was autoclaved at more than 7 or 6 of LIF, respectively.
Though products A and B should be used for sterilization of materials such as surgical instruments by saturated steam, it was found that when the method to immerse CI in a filling solution was chosen, the use of these CI's in addition to the thermometer gives greater validity to verifying sterility of parenteral solution in hospital pharmacy.