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Spring 1997 - Article 3

From The Lab
Quaternary Disinfectants- How They Work

Quaternary biocides are used in numerous products such as disinfectants, algaecides, sanitizers and fungicides to kill or control the growth of undesirable organisms.

In their purest form, quaternary biocides are nothing more than cationic surfactants (surface active agents) that carry a positive charge. On the other hand, bacteria, viruses, fungi, etc., carry a negative charge due to the presence of amino, carboxyl or phosphate groups on their surface. Therefore, when a bacteria-laden surface is sprayed or mopped with disinfectant, the charge distribution of the bacteria cell surface changes from negative to positive resulting in disruption of the cell wall causing the organism to die.

There are three important factors that influence efficacy when disinfecting a surface: dilution rate, contact time and soil load.

1. Dilution Rate:
   Proper dilution allows enough quat to saturate the surface being disinfected. Dilution control devices such as System 2000™ are perfect for delivering the right amount of quat.
2. Contact Time:
   Contact time is critical since the mechanism explained above does not occur instantaneously. Cell walls take time to break down. This is why disinfectant labels list 10 minutes as the desirable contact time.
3. Soil Load:
   Heavily soiled surfaces should be pre-cleaned prior to disinfection since disinfectants can't tell the difference between bacteria and soil. This "competition" for quat between soil and bacteria reduces efficacy.

If you follow these three guidelines, proper disinfection will occur.

Before the surface is sprayed or mopped with a disinfectant.
After the surface has been sprayed or mopped with a disinfectant.