Colloid and Surface Science Aspects in Disinfectants

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Colloid and Surface ScienceAspects in
Disinfectants

• Reginald Jacques
• Garret Lau
• Carla Ng
• Pintu Saha
• University at Buffalo, Department of Chemical
  Engineering

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Overview

• Major Uses
• The Disinfectant Market
• Product Considerations
• Disinfecting Agents
• Colloids in Disinfectants
• Interactions and Structure-Property Relationships
• Disinfectants of the Future

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What is a disinfectant?

• Agent that kills actively growing micro-organisms
  (bacteria, viruses, fungi, etc.) but does not
  kill their spores.
• Purpose prevention of sickness caused by these
  microorganisms.

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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)

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Product Specifications

• Selective toxicity want to kill bacteria,
  viruses, other pathogens remain safe to humans
  and general environment
• Government regulations must abide by rules and
  regulations imposed by EPA, FDA
• Household considerations
• 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)

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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)

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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

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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.

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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 includebutylated hydroxy
  toluene, glutaraldehyde and so on.
• Organic solvent Help in removing spots without
  leaving any residue.

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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 Colloidsis 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

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Association Colloids

• Mainly used in the fabrication of disinfectant
• Examples of this type of colloid micelles,
  reverse micelles, vesicles, micro-emulsions.

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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.

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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(2-ethylhexyl) Sulfosuccinate
  (Aerosol-OT)
• Long term exposure can lead to skin irritation

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Main Components and Compositions of Disinfectants
for Household

• Alcohol Compounds
• Chlorine Compounds
• Iodine Compounds
• Quaternary Ammonium Compounds

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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

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Chlorine Compounds

• Antibacterial action of chlorine compounds
  dependent upon their capacity for releasing
  active chlorine
• Sodium Hypochlorite
• Chlorine Dioxide
• Products
• Drinking Water
• Cleaners

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Iodine Compounds

• Aqueous Solutions
• Alcoholic Solutions
• Iodophric Preparations
• Products
• Drinking Water
• Health Care Products Antiseptic

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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

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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

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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

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Mechanism of Antibacterial Activity

• Adsorption onto cell surface
• Diffusion through cell wall
• Binding to the cytoplasmic membrane
• Disruption of the cytoplasmic membrane
• Release of cytoplasmic constituents
• Cell death

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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.

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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.

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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.

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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

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QUESTIONS?