The pH must be what for iodine when used for cleaning?

• A. 7.0 or less
• B. 6.0 or less
• C. 4.0 or less
• D. 5.0 or less

Answer: (D)

Lower pH makes iodine more effective as a sanitizer because acidic conditions increase the amount of active iodine available to kill microorganisms. Iodine-based sanitizers release iodine more readily at lower pH, so keeping the solution in a mildly acidic range enhances disinfection.

In practice, the guideline is to keep the pH at 5.0 or below. If the pH is higher, the active iodine concentration drops and disinfection becomes less reliable, which may require longer contact times or higher concentrations. At the same time, very low pH can be corrosive to some materials, so aiming for 5.0 or below balances efficacy with safety for surfaces and equipment. Regularly check and adjust the sanitizer’s pH to stay in that range using appropriate acid and testing methods.