A medical instrument processor includes an enclosure, a liquid distributionsystem, and adisinfectant concentration measuring subsystem. The enclosure is configured tohold a medicalinstrument. The liquid distribution system is configured to deliver adisinfection solution to amedical instrument within the enclosure. The liquid distribution system has aliquid outlet. Thedisinfectant concentration measuring subsystem includes a first mixing chamberin fluidcommunication with the liquid outlet, a pump that is configured tosimultaneously pump thedisinfection solution and the reagent solution into the first mixing chamber,and a concentrationanalysis assembly that is operable to determine a concentration ofdisinfectant in a samplesolution that is output from the first mixing chamber. The reservoir is influid communicationwith the first mixing chamber.
