Neutralization of the activity of eight disinfectants by organic matter

The effect of organic matter on the activity of eight disinfectants was evaluated. Three types of interfering substrates (whole milk powder, dried beef blood and fish meal) were tested according to the method of Whitmore and Miner adapted to the AOAC use-dilution method. Glutaraldehyde and to a certain extent, chlorhexidine acetate and the amphoteric surfactant kept their disinfecting activity after contact with high concentrations of organic matter. The quaternary ammonium compound as well as the quaternary ammonium-glutaraldehyde complex were more readily neutralized whereas anionic acid, iodophor and sodium hypochlorite did not tolerate the presence of organic matter. The neutralizing activity of powders was correlated to their solubility and composition.