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

Overview

• 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 micro-organisms (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• 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)

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(2-ethylhexyl) Sulfosuccinate (Aerosol-OT)

• Long term exposure can lead to skin irritation

Main Components and Compositions of Disinfectants

for Household

• 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

ProductsFood

Health Care Products

Chlorine Compounds

Antibacterial action of chlorine compounds dependent upon their capacity for releasing

“active” chlorine • Sodium Hypochlorite

• Chlorine DioxideProducts

Drinking WaterCleaners

Iodine Compounds

• Aqueous Solutions

• Alcoholic Solutions

• Iodophric Preparations

ProductsDrinking 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.

ProductsContact 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

• 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?