Colloid and Surface Science
Aspects in Disinfectants
Reginald Jacques
Garret Lau
Carla Ng
Pintu Saha
University at Buffalo, Department of Chemical Engineering
Overview
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Major Uses
The Disinfectant Market
Product Considerations
Disinfecting Agents
Colloids in Disinfectants
Interactions and Structure-Property
Relationships
• Disinfectants of the Future
What is a disinfectant?
• Agent that kills actively growing microorganisms (bacteria, viruses, fungi, etc.) but
does not kill their spores.
• Purpose – prevention of sickness caused by
these microorganisms.
Application of Disinfectants
• Food industry – sanitize food preparation areas,
preservative functions
• Drinking water – typically chlorine, other organic
oxidizers
• Medical – sterilization of equipment, facilities
• Household – cleaners (kitchen, bathroom, multipurpose),
soaps, detergents
• Other industries – paints, inks, cosmetics (serves as
preservative)
Product Specifications
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Selective toxicity – want to kill bacteria, viruses,
other pathogens; remain safe to humans and general
environment
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Government regulations – must abide by rules and
regulations imposed by EPA, FDA
Household considerations
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multipurpose products: disinfectant combined with
surfactant for grease removal, or moisturizers as in soaps
dispersive quality: aerosol or spray for coverage and
adhesion to hard surfaces (countertops, bath, toilet, etc)
Further Considerations
• Marketing - Between 1997-1999, manufacturers
introduced 700 new antibacterial or disinfectant
products; half of $2.1 billion cleanser market in
US; bacterial resistance?
• Cost ($2-$4 for 32 oz. Shower cleaner) – compare
active ingredient of brand names with generic
• Processing/Packaging – liquid detergents, soaps
(plastic bottles); aerosol spray (aluminum cans);
polymerized disinfectants (chemically
incorporated into fabric or material)
Ingredients of Disinfecting Cleaners
• Builders: Tie up the hardness minerals in water so they
do not interfere with the cleaning action of the surfactant
 Builders are subdivided into into three categories: Sequestering,
precipitating and Ion exchange builders.
• Abrasive: Contribute to the mechanical effectiveness of
scouring cleanser; consist of small mineral particles.
• examples: Silica, feldspar, calcite
• Acids: Dissolve calcium and metal salt in tub, tile, sink
and toilet bowl cleaners.
 Type of acids: Phosphoric, Hydrochloric, hydroxyacetic acids
• Alkalis: maintain pH at a desirably high level during
cleaning; play a crucial role in removing solid grease.
 Types of alkalis are: sodium Hydroxide, Sodium metasilicate,
sodium carbonate
Other important ingredients
• Antimicrobial agents: Destroy bacteria and viruses, by
interfering with their metabolism or destroying their cell walls.
 Examples: Alcohol, sodium hypochlorite, iodine, pine oil etcetera.
• Bleaching agents: Oxidize the soil and stain to a more easily
removable form. Attack the soil and destroy bacterial viruses and
mold.
 Sodium hydroxide is very effective for that purpose.
• Colorants: Give an appealing characteristic to the product, can
also be tracers.
• Enzymes: Break down the soil into a simpler form that can be
removed.
• Polymer: They are very helpful in floor care product, they protect
the surface and provide shine.
Other important ingredients
• Processing aids: keep the product homogeneous
under different storage conditions.
 Most used processing aids are: Clays, polymers, Sodium
Silicate and Sodium Sulfate
• Preservatives: Protect the product against decay,
discoloration,oxidation and bacterial attack
 Typical preservatives include:butylated hydroxy toluene,
glutaraldehyde and so on.
• Organic solvent: Help in removing spots without
leaving any residue.
Type of colloids
• Hydrophobic Colloids: is
a colloid in which there is a strong
attraction between the dispersed phase
and the continuous phase (water)
• Hydrophilic Colloids:is a
colloid in which there is a lack of
attraction between the dispersed phase
and the continuous phase (water)
• Association Colloids: They
are described as molecule that has two
part in their configuration., a
hydrophobic part and a hydrophilic part
Association Colloids
• Mainly used in the fabrication of disinfectant
• Examples of this type of colloid: micelles, reverse
micelles, vesicles, micro-emulsions.
SURFace ACTive AgeNT
• They are often portrayed
as having a head and a
tail.
• Molecule that adsorbs at
the surface and/or
interface.
• They are described as
being amphiphilic.
• Types of surfactants:
anionic, cationic, nonionic,
amphoteric.
Anionic Surfactant
• Are used in the fabrication of disinfectant
• They are used all over the place, and their composition
represent almost half of all the other surfactant are made
of.
• They are sometimes used in conjunction with nonionic to
provide greater stability.
• Type of nonionic surfactants that are used in disinfectant
are :
 Fatty acids (soaps):
 Sodium Oleate, Sodium Palmitate, Sodium Myristate etcetera.
 Alkyl Sulfates:
 Sodium Dodecyl Sulfate (SDS)
 Other commonly used Anionic Surfactant:
 Alkyl Benzene Sulfonates, 2-Alkyl Phosphate, Sodium di(2ethylhexyl) Sulfosuccinate (Aerosol-OT)
• Long term exposure can lead to skin irritation
Main Components and
Compositions of Disinfectants
for Household
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Alcohol Compounds
Chlorine Compounds
Iodine Compounds
Quaternary Ammonium
Compounds
Alcohols
Inhibition increases with the chain length.
• Methyl Alcohol
– Not included in most household goods.
• Ethyl Alcohol
– Effective germicide for vegetative pathogens
• Isopropyl Alcohol
– Effective germicide for an antimicrobial agent
Products
Food
Health Care Products
Chlorine Compounds
Antibacterial action of chlorine compounds
dependent upon their capacity for releasing
“active” chlorine
• Sodium Hypochlorite
• Chlorine Dioxide
Products
Drinking Water
Cleaners
Iodine Compounds
• Aqueous Solutions
• Alcoholic Solutions
• Iodophric Preparations
Products
Drinking Water
Health Care Products {Antiseptic}
Quaternary Ammonium
Compounds
• Aliphatic long-chain ammonium salt
• Owe their surface activity and antibacterial
qualities primarily to the presence of
aliphatic long-chain amino groups.
Products
Contact Lens Solution
Designing an Effective Disinfectant
• Know your dirt
– What type of surface?
• Soil effect on disinfectant action:
– Oily residues are impervious to water and often contain
germs.
– Bacteria can form biofilms to protect against attack.
• Consumer considerations
– Fragrance
– Irritants
– Environmental Concerns
Overcoming Biofilms and Organic
Residues
• Disinfectants disrupt bacterial cell function.
• Many common disinfectants are effective
biocides, but are inactivated by organics.
• Components must be added to aid
disinfectants in reaching and affecting
bacterial cells  Surfactants
Mechanism of Antibacterial
Activity
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Adsorption onto cell surface
Diffusion through cell wall
Binding to the cytoplasmic membrane
Disruption of the cytoplasmic membrane
Release of cytoplasmic constituents
Cell death
How Surfactants Aid Disinfectants
• Surfactants can help by:
– Removing surface residues and biofilms
– Aiding the germicide action of disinfectants
• Some surfactants are biocides themselves.
• Surfactants can facilitate disinfectants by disrupting
the bacterial cell membrane.
Structure-Property Relationship
• Structure of surfactant will dictate how it
interacts with bacteria.
Example:
Surfactants containing polar ethylene oxide chain:
– Chain too small, no disruption
– Chain too long, no disruption
– Chain same order as lipid bilayer, cell
membrane disruption cell death.
Structure-Property (continued)
• Critical Micelle Concentration (CMC) and
germicidal activity are linked:
CMC
antibacterial properties
CMC related to hydrophobicity, charge
distribution, molecule shape.
These characteristics affect the interaction of
surfactant with microbial cell.
Disinfectants of the Future
• Understanding what makes disinfectants
work leads to new improved formulations:
– Environmentally friendly disinfectants
glucose-based cationic surfactants
– Polymers as disinfectants
disinfectant coatings
insoluble disinfectants
QUESTIONS?