Systematic error associated with apparatus 2 of the USP dissolution test IV: effect of air dissolved in the dissolution medium.

Acceptable concentrations of gases in a medium are not well defined in USP dissolution tests. A sample of 10-mg prednisone tablets, known to be sensitive to dissolved gases, was tested with batches of purified water that contained different concentrations of air. The data suggest that the results from Apparatus 2 can be influenced by the concentration of air in the dissolution medium unless the medium remains unsaturated with air for the duration of the test. The repeatability of means of six results was markedly improved when the air concentration in the medium was accurately controlled at the beginning of the test.