Methods for determining the amount of residual sterilant remaining on the surface of an object at the end of a disinfection process are described. One method of determining the amount of residual sterilant on a test piece after a sterilization regime in a sterilization space, the method comprises the steps of: placing a test piece having a predetermined surface area into the sterilization space subjecting the test piece to the sterilization regime collecting the residual sterilant from the test piece in a collector solution and measuring the amount of residual sterilant in the collector solution.
