This is a general-purpose neutralising diluent used particularly in the pharmaceutical industry. Lecithin, L-histidine and Tween 80 are present to inactivate surface disinfectants such as quaternary ammonium compounds, phenols, aldehydes (including formaldehyde), hexachlorophene and ethanol. The diluent may be used in sampling surfaces and equipment (including endoscopes) to detect the presence of surviving microorganisms after disinfection. The presence of the surfactant Tween 80 also helps release adherent organisms from surfaces being tested.