Quaternary Ammonium – Quats

Quats were first created in 1915, though they were not commercially available until 1935. These are not natural compounds. They have been engineered and improved over the course of time. The latest generation of quats, the fourth, was introduced in 1979. Quats inhibit enzyme activity and disrupt the cell membrane to kill or inactivate microorganisms. Most people refer to them only as “quats”, or by generation number, e.g. “4th”.

The first generation of quats showed many favorable characteristics:

• Good Features
• Relatively low toxicity
• Broad spectrum of kill
• Water soluble
• One-step cleaner, disinfectant
• Poor Features
• low tolerance to hard water
• inactivated by anionics
• low tolerance to organic soil load

The second generation, introduced in 1955, addressed the issue of hard water tolerance by increasing the quats ability to kill in harder water.

Third generation, introduced in 1965, quats continued the work of making quats better suited to conditions in the real world. The features added to the third generation of quats are:

• effective at lower use dilution (better value)
• increased hard water tolerance (even more than 2nd generation)
• protein tolerance (organic soil load)
• anionic residue tolerance

The fourth generation of quats pushed hard water and organic soil tolerance even further and improved its synergistic capabilities.

• excellent hard water tolerance (e.g. to 400ppm)
• organic soil load tolerance 2-3 times better than 1st generation
• excellent performance with half the ppm of quat as 1st generation through synergistic activity

Phenolic Compounds

Another name for phenol is carbolic acid, but this name has gone out of common use. Phenol has been in use since 1842 as a disinfectant during surgery. Phenols work by disrupting the microorganism’s cell membrane and denaturing proteins. In spite of the positives of disinfection during surgery, phenol was found to be a toxic and corrosive chemical. Among phenol’s many positive qualities are:

• broad spectrum antimicrobial activity
• tuberculocidal
• combines well with cleaners (though not nonionics, which inactivate it)
• tolerant of hard water and organic load

Since the 1800’s chemists have altered phenol by adding components to the basic molecule to improve its characteristics and make it safer to use. Among the improvements are:

• lowered oral toxicity
• minimum odor
• more stable

There are still a few drawbacks to phenolic compounds which you should be aware of.

• not water soluble
• inactivated by nonionics
• linked to hyperbilirubinemia in infants (neonatal jaundice)
• linked to skin depigmentation

Halogen Compounds

Halogens are a family of chemical compounds which includes Chlorine, Fluorine, Bromine and Iodine. These compounds have long been used for disinfection. They kill or deactivate microorganisms by inhibiting the protein functions, the enzyme activity, the DNA of the organism, or by denaturing the organism’s proteins.

The beneficial features of halogens include:

• broad spectrum kill
• fast acting
• may be used on food contact surfaces
• Chlorine is used to purify 98% of the U.S. drinking water

Negative characteristics of halogens include:

• corrosive (even to some stainless steel)
• odor and taste unpleasant
• poor wetting ability on their own
• unstable in solution
• limited organic tolerance
• Iodine stains
• Chlorine bleaches

Aldehydes

Formaldehyde and Glutaraldehyde are two examples of the aldehyde family group of chemical agents used to kill microorganisms. The aldehyde group kills microorganisms by coming with many protein functional groups to inactivate the organism.

Beneficial features of aldehydes:

• broad spectrum, high level disinfectant and sterilant
• tolerant of organic load
• non-corrosive to rubber, plastic and metal

Negative characteristics of aldehydes are:

• irritating fumes and pungent odor
• toxic
• formaldehyde is a suspected carcinogen
• not cost effective for environmental disinfection

Applications for aldehydes:

• Cold sterilization of heat sensitive instruments and equipment
• Glutaraldehyde can be made into either acidic or alkaline solutions, usually at 2% concentration. It must be on the alkaline side to be sporicidal.
• Used for cold sterilization and general disinfection.
• Formalin is a 37% solution of formaldehyde, used at one time in embalming and preservation.

However, due to its strong odor, irritation and the suspicion that it is a carcinogen, its use has declined.

Heavy Metals

Arsenic, Copper, Mercury, Silver, Tin and Zinc are all members of the group known as heavy metals. Mercury has been reported in use as long ago as 1140 A.D. Heavy metals work by denaturing enzymes and other essential proteins of the microorganism.

Negative characteristics:

• Environmental disinfection is very limited due to the difficulty in processing the heavy metal itself out of the waste water stream.
• The extreme toxicity of heavy metals is believed to have caused the widespread killing of fish and bacteria in natural water systems.

Applications: This group is used mainly for antiseptic applications in small quantities. For instance, silver nitrate is used for washing newborn babies’ eyes.

Alcohols

The term “medicinal wine” probably comes from the long standing use of alcohol as a disinfectant or sanitizer. In 1903, testing showed a 60 to 70% concentration of alcohol was best for disinfection. Alcohol kills because of solvent activity on membrane, lipids and denaturing of proteins. Ethanol and isopropyl alcohol are two common examples of alcohols used in sanitizing and disinfection. Another name for isopropyl alcohol is isopropanol.

Advantages:

• rapid activity against vegetative bacteria, fungi and enveloped viruses
• used routinely for skin antisepsis and waterless skin sanitizing
• combine with other ingredients to improve performance of formula
• leaves no residue

Disadvantages:

• ineffective against bacterial spores and non-enveloped viruses
• highly flammable
• rapid evaporation reduces contact time
• 70% concentration makes formulas expensive
• damages finishes and rubber parts