colloid and surface science aspects in disinfectants reginald jacques garret lau carla ng pintu saha...
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Colloid and Surface ScienceColloid and Surface ScienceAspects in DisinfectantsAspects 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 include:butylated 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 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
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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
ProductsFood
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 DioxideProducts
Drinking WaterCleaners
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Iodine Compounds
• Aqueous Solutions
• Alcoholic Solutions
• Iodophric Preparations
ProductsDrinking 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.
ProductsContact 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?