Selective toxicity of alkanolamines.

The antimicrobial effects of diethanolamine, dimethylamino-methyl-propanol, and butylethanolamine are greatly enhanced at high pH. Their antimicrobial activities are closely correlated with their uncharged forms, indicating that diffusion through cell membrane(s) is rate limiting for the antimicrobial action. Since these compounds are selectively toxic at high pH, they are appropriate antimicrobial agents for use in alkaline metalworking fluids.