Colloid and Surface Science
Aspects of Disinfectants
Reginald Jacques
Garret Lau
Carla Ng
Pintu Saha
University at Buffalo, Department of Chemical Engineering
INTRODUCTION
3
PRODUCT AND CONSUMER CONSIDERATIONS
4
MARKETING
5
COMPONENTS AND COMPOSITIONS OF DISINFECTANTS FOR
HOUSEHOLD USE
6
General Components of Cleaning Solutions
6
Common Disinfecting Chemicals
9
COLLOIDS IN DISINFECTANTS: SURFACTANTS
13
STRUCTURE-PROPERTY RELATIONSHIPS
18
DISINFECTANTS OF THE FUTURE: CURRENT RESEARCH
23
2
Introduction
Disinfectants represent a wide range of substances that are used in various
applications. The food industry requires the use of disinfectants to sanitize food
preparation areas, and serve preservative functions. Chlorine and other organic oxidizers
are employed for the purification of drinking water. Hospitals and clinics rely on
disinfectants to sanitize their medical facilities. Disinfectants are even used for their
preservative abilities in paints, inks, cosmetics, and other industries. And of course, the
disinfectants most people are familiar with, household disinfectants, serve to help us with
controlling germ and bacteria levels in our kitchens, bathrooms, and bodies. Despite the
variety in disinfectant materials, they all strive for one desired characteristic: selective
toxicity. Disinfectants are engineered to kill bacteria, viruses, and mildew, yet be safe to
possible human contact.
In the United States, the primary regulations that disinfectants must abide by are
established by the Environmental Protection Agency (EPA) and the Food and Drug
Administration (FDA). The EPA regulates drinking water purification, finding ways to
limit or replace chlorine as a disinfectant, fearing the biological contamination of organic
chlorinated byproducts (w4). Household disinfectants found in soaps and other cleaners
are regulated by the FDA, where products are tested and examined for public health and
3
safety (w6). While many disinfectants pass through government agencies for safety
approval, we chose to focus our scope on common household disinfectants.
Product and Consumer Considerations
Household disinfectants must meet several criteria. Besides having anti-microbial
properties and being safe to use around humans and the environment, household
disinfectants are almost exclusively incorporated into a cleaner that provides
multipurpose capabilities, aside from just killing germs. A 1996 Hard Surface Cleaner
Market Study determined that consumers desire cleaners that disinfect, cut grease,
deodorize, and at the same time be cost effective (14). Bathroom cleaners were expected
to remove soap scum and stains while leaving no film or residue (14). Cleaners must
possess a dispersive quality – the ability to be sprayed or spread onto a surface for the
necessary time required for disinfection and cleaning. This often means the incorporation
of surfactants and the use of colloidal properties. Soaps and detergents frequently contain
moisturizers to alleviate the harsh conditions on the skin. Despite these many
considerations in household cleaners, disinfectant and antibacterial properties are among
the most important aspects of cleaners consumers use most often.
While consumers worry about the sterilization capability of cleaners, a distinction
must be made between the degrees of sterilization. Many common household cleaners
are simply antibacterial. Hand soaps and liquid dish detergents contain triclosan, also
known by its trade name Microban, which is strictly an antibacterial (5). Salmonella, E.
coli, and bacteria that cause strep throat and staph infections are typically the common
targets of triclosan. A true disinfectant also kills viruses and other pathogens along with
4
bacteria. Alcohols, bleach (sodium hypochlorite), quaternary ammonium compounds,
and certain oils comprise the most familiar household disinfectants. All disinfectants
used in household cleaners must meet EPA or FDA approval. Regulations outlined by
the EPA include stringent tests against Salmonella choleraesuis, Staphylococcus aureus
and other bacteria, along with a performance mandate that in order to be termed a
disinfectant for use on hard materials, the disinfectant must kill on 59 out of each set of
60 carriers and is required to provide effectiveness at the 95% confidence level (w5).
Marketing
The increasing popularity of disinfectants in common household products is a
recent trend. Between 1997 and 1999, manufacturers introduced 700 everyday products
claiming antibacterial or disinfectant properties (5). Disinfectant cleaners make up half of
the $2.1 billion cleanser market in the United States (15). Marketing household
disinfectants is not about convincing consumers to sterilize their homes – studies show
consumers already have this fear. Rather, the effectiveness of the cleaner in cleaning and
disinfecting as compared to other brands is important, along with its relative price
compared to other brands. Brand name cleaners may not necessarily provide a better
product – often generic brands contain the same concentration of active ingredients.
Final product considerations reside in packaging and sales factors. Typical
cleaners sell for $2-$4 for 32 ounces, representing the smaller sample size for household
use (5). Packaging of disinfectants mostly involves the chemically inert plastic bottles
that cleaners are supplied in. Variations exist in the aluminum spray cans for aerosol
cleaners, and now technology is finding ways to introduce disinfectants into other
5
mediums. N-halamine structures have been polymerized with a grafting process into
cellulose containing and nylon fabrics, giving everyday materials anti-microbial
properties within themselves (16). Triclosan is also being incorporated into a polymer for
use in fabric seat covers, tables, chairs, and clothing sanitation (9). With so many
methods of incorporating disinfectants into the household and the relative
inexpensiveness of processing these materials, there seems no immediate decline to the
increasing market of disinfectant products.
Components and Compositions of Disinfectants for Household Use
General Components of Cleaning Solutions
There are seven main ingredients found in most household cleansers. These are (in order
of decreasing amount) (w12):
(1) Surfactants: these are amphiphilic molecules which serve several purposes in a
disinfecting cleaner:
a) they adsorb to surfaces, where they aid in loosening and removing soils
b) they hold particles in suspension and prevent redeposition on the surface
c) they cause “wetting” be reducing the surface tension of water and allows it
to spread over the surface
d) anionic (negatively charged) surfactants are best against particulate dirt
and oily soils, but can react with minerals in hard water to form scum
e) cationic (positively charged) surfactants are effective as germicides on
hard surfaces
6
f) nonionic surfactants have no charge and therefore are able to work even in
hard water, are low foaming and well-suited for no-rinse applications ().
Surfactants will be treated in greater detail in later sections of this report.
(2) Builders: these compounds are primarily responsible for reacting with hardness
chemicals (such as calcium and magnesium) to keep them from interfering with
surfactant action; in other words, they are water softeners. They can also aid in
keeping soil particles in suspension, and are especially useful in all-purpose
cleaners. These are found in three types:
(a) sequestering builders form tightly-bound, water-soluble
complexes with Ca and Mg ions
(b) precipitating builders form insoluble calcium compounds, which
will then need to be removed from the surface as it is cleaned
(c) ion exchange builders “neutralize” hardness mineral through
electrical charge exchange.
(3) Abrasives: these particles are added to increase the mechanical cleaning ability of
a product. They usually consist of small hard particles. Some examples are silica,
calcite and feldspar.
(4) Acids: these are used to dissolve calcium and metal salts. They are common in
“tub-and-tile” type cleaners used in the bathroom.
(5) Alkalis: these chemicals give cleaning solutions a high pH and help remove solid
grease, as well as providing some building action. Mild alkaline chemicals, such
as baking soda, may be used in products formulated for contact with skin.
7
(6) Antimicrobial agents: these are the focus of our report, and are chemicals that
destroy bacteria and viruses, as well as (in some cases) fungi. These agents must
be registered with the EPA before they can be sold. A description of the most
common disinfecting agents follows this section.
(7) Bleaching agents: these components attack dirt by chemical breakdown, normally
via oxidation. Stains are broken down into smaller, colorless forms that are easier
to remove. The most common bleaching agent is sodium hypochlorite, which is
capable of destroying bacteria, viruses and mold.
In addition to these major components, household disinfectant products may contain:
colorants, which provide a purely aesthetic effect; enzymes, which are capable of
breaking down specific organic soils; fragrances, to cover the base odor of the cleaning
solution as well as leave a pleasant, “clean” scent behind; polymers, which can be used in
floor cleaners to provide a shiny, dirt-repelling film after drying, or in more general
cleaners as building or thickening agents; processing aids, which keep the product from
separating during storage and helps give it the desired dispensing characteristics;
preservatives, which protect against bacterial attack; and solvents, which are particularly
useful in the removal of grease without leaving a residue, such as is desired with glass
cleaners.
In the following sections we will describe in greater detail disinfecting chemicals
and surfactants, the two key components in household disinfectants.
8
Common Disinfecting Chemicals
Disinfectants for household use are divided into four main subcategories, as
follows: alcohol, chlorine compounds, iodine compounds and quaternary ammonium
compounds. These disinfectants are active at many pH levels. Iodines, for example, are
most effective in the lower pH ranges, from ~2-6, whereas chlorines work best at the
higher end, from 6-10. Quaternary ammonium compounds are the most versatile, with a
working range between 3 and 10.5 (2, Fig 23.1, p.477). For this reason, household products
containing disinfectants are similarly solutions at various pH levels.
Alcohols
One of the most common chemicals present in
the average person’s medicine cabinet is rubbing alcohol.
It is often used as an antiseptic to clean minor wounds,
and also as a hard surface cleaner. Like many chemical
disinfectants, alcohols are generally considered to be
nonspecific antimicrobials. They show a multiplicity of toxic effect mechanisms. This
has important implications for the spectrum, speed and overall effectiveness of alcohol as
a disinfectant. Not all alcohols show bactericidal effect; the amount of inhibition
increases with the chain length of the alcohol (see 10, Table1, p.800).
Chlorine Compounds
9
Chlorine compounds are some of the most active ingredients in disinfectants. Use
of chlorinated lime as a deodorant for sewage goes as far back as 1854 in Great Britain.
Calcium hypochlorite has now largely replaced the older chlorinated lime, and sodium
hypochlorite is th emost active principle of many household products. Various types of
algae, bacteria, fungi, protozoa and viruses have shown resistance to hypochlorites (2,
Table 7.1, p.143).
The bactericidal action of hypochlorites is caused by the release of
hypochlorous acid and contributions of hypochlorite ions (OCl-). Hypochlorites are
subject to gradual deterioration over a period of time, which depends on three main
factors. The most important factors are the pH and temperature of the environment. The
lower the pH, the less stable the solution, but the more germicidal its action.
Chlorine dioxide is used a great deal for drinking water and wastewater treatment
(2).
It has the ability to break down phenolic compounds and removes phenolic tastes and
odors from water. There are numerous antimicrobial chlorine compounds, but a major
advantage of this particular formulation is that is does not form trihalomethanes (THMs)
or chlorophenols, which are both harmful to the environment and have been coming
under scrutiny by environmentalists making groundwater studies.
The major advantages of chlorine compounds are that they have very fast reaction
times and are effective biocides for a broad spectrum of microorganisms. They are
inexpensive compounds that do not foam, are not temperature dependent, and can be used
in liquid or powder form. The main disadvantages are that chlorine is unstable in
concentrate. It reacts strongly with organic materials and is corrosive to metals. More
importantly, it is unfriendly to the environment.
10
Iodines
Iodine, the heaviest of the common halogens (126.9 g.mol),
melts at 113.5ºC to a black liquid, and is a valuable ingreadient in
antiseptics. Iodine is a highly reactive substance combining with
proteins partly by chemical reations and adsorption. Iodine-based
disinfectants can be divided into three main groups according to the
solvent and substances interacting with the iodine species: pure
aqueous solutions, alcoholic solutions and iodophoric preparations.
They exhibit essential differences in their chemical and microbiocidal properties. The
iodine compounds not only kill microorganisms but also interact with the materials to be
disinfected. To understand these interactions, knowledge about the particular species,
solvent, equilibrium concentrations and individual reactivity is essential.
Iodine ions are often added to increase the solubility of iodine in water. This
increase takes place by the formation of triiodide, I3-. Pure aqueous solutions, for the
iodine-water system, produce at least ten iodine species:
I-, I2, I3-, I5-, I6-, HOI, OI-, HI2O-, I2O2-, H2OI+, and IO3-.
The ratio of their formation depends on the concentration of iodine.
Iodophors are polymeric organic molecules, such as alcohols, amides and sugar,
which are capable of forming iodine species. This results in reduced equilibrium
concentrations of species compared with those of pure aqueous solutions with the same
total iodine and iodide concentrations. Since iodophoric preparation always contains
appreciable iodide, the relevant species tat must be considered are restricted to I-, I2 and
I3-, for the following simplified reactions (2, p.168):
I2 + R  R.I2
11
I3- + RR.I3I-+ R R.IR represents the structural regions of the iodophor molecule capable of forming
complexes by electronic effects.
An important solubilizing agent and carrier for iodine is poly(vinylpoyrrolidinone)
(PVP). PVP-iodine is externally used on humans as an antiseptic. Some commercial
brands are Betadine and Isodine.
Quaternary Ammonium Compounds
Quaternary ammonium compounds are often used in
contact lens solutions for cleaning and preservative purposes.
The antibacterial precursors of the quaternary ammonium compounds (“quats”)
are aliphatic long-chain ammonium salts. The direct counter part of soap may be
considered as a primary ammonium salt. Both are surface-active substances. In soap, the
anion contributes the hydrophobic part and the primary ammonium salt (the cation) is
hydrophobic.
The primary long-chain ammonium salts are derived from the weakly basic
aliphatic amines. Their aqueous solutions require a pH low enough to counteract
hydrolysis and partial liberation of the amine base. Because quats ae salt bases, they
remain in solution in acidic as well as in basic media. Quaternary ammonium salts
produce bacteriostasis in very high dilutions. This property is associated with the
12
inhibition of certain bacterial enzymes, especially those involved in respiration and
glycolysis.
Among the many quaternary ammonium salts available, only a small number are
of interest as antibacterial agents. Among them are: benzalkonium chloride,
alkylbenzyldimethylammonium chloride, methydimethyl ammonium chloride,
methylbenzethonium chloride, hexadecylpyridinium chloride, and alkylisoquinolinium
bromide (10).
It is evident from the varied examples of disinfectant chemicals above that we as
consumers have a wide range of products to choose from when it comes to ridding our
homes of germs. Each has specific properties, advantages and disadvantages and it is
important to keep this in mind, as well as the intended use, when choosing an appropriate
cleaning product.
Colloids in Disinfectants: Surfactants
Colloid science is concerned with the study of materials that exist as dispersions
in a medium of some other material. They are sometimes defined as particles that would
remain suspended in water for an extended amount of time. A colloid differs from a true
solution in that the dispersed particles are larger than normal molecules, though they are
too small to be seen with a regular microscope. The typical size of a dispersed particle is
from a few nanometers to several micrometers. One consequence of this small size is a
high surface area, so that the properties of the interfaces may become important. The
common element among all the types of colloids is the fact that they are held in
13
suspension by electrostatic interaction with water molecules. Another important
parameter is the thermal motion, which dominates the dynamic properties. Crucial
examples include, food, paint, and household products (12).
Colloids in which the continuous phase is water are classified as follows:
hydrophilic colloids, hydrophobic colloids and association colloids. The first two types
differ from each other by their chemical configuration and/or composition.
Hydrophilic colloids are large molecules that contain functional groups as an
integral part of their structure. The functional groups form hydrogen bonds with water
molecules. Common examples of hydrophilic colloids are proteins and synthetic
polymers. Two examples of hydrophilic colloids are depicted below (11):
Figure 1: Hydrophilic colloids
Hydrophobic colloids are substances that have charged surfaces in water, and
form an electrical "double layer" that holds them in suspension. Clays form a negative
charge on their surface when placed in water, and remain in suspension by the
electrostatic interaction between the negative surface charge and positive charges from
14
cations in the water. The figure below depicts the colloidal clay particles that are
suspended in solution by electrostatic
interaction (11).
Figure2: Hydrophobic Colloid
The third type of colloid is an
"association" colloid. These are
molecules that have two parts to their molecular structure, a hydrophobic part and a
hydrophilic part. They are also known as surfactants. As they are often the most
important component present in a cleaning solution, they will be considered here in more
detail.
Soaps and detergents form association colloids in water. Their molecular structure
is similar to the illustration below, where the carboxylic acid group is the hydrophilic
portion and the hydrocarbon chain is the hydrophobic part of the molecule (w8).
Figure3: 'association Colloid
Association colloids are the type that is used in the fabrication of disinfectants
because they possess some germicidal properties. They are also used in cationic
detergents. Association colloids form self-assembly systems. Some examples of these
15
systems are micelles, reverse micelles, vesicles, micro-emulsions and the monolayers and
bilayers of some cell membranes. These monolayers and bilayers represent the building
blocks of biomembranes (w2).
The word surfactant describes the activity of the molecule. They are SURFace
ACTive AgeNTs; in other words a surfactant is a molecule that tends to align itself at a
surface or interface. Surfactants fall into four broad categories: anionic, nonionic,
cationic and amphoteric. They are described as being amphiphilic, in a sense that they
have strong attraction towards both polar solvents (hydrophilic) and non-polar solvents
(hydrophobic), and as a result they will concentrate at the interface between the two (11).
Surfactants are often portrayed as having a head and a tail. The head is said to be
hydrophilic, it can either be ionic or non-ionic, and it is usually depicted as a circle. The
tail is said to be hydrophobic and it is generally represented as a long hydrocarbon chain.
The hydrocarbon is “water-hating” which thus means it is “oil-loving”. Normally
surfactants lower the surface tension of water. Schematics commonly used to depict
surfactants are shown below, along with the formula for an actual surfactant (11):
Figure 4: Anionic Surfactant
16
Surfactants are often characterized by their configurations. Sodium Oleate is an
example of a molecule that can be classified as surfactant. It is a type of surfactant that is
commonly used in the fabrication of disinfectants. The oleate ion is derived from triolein,
(a triglyceride), by the hydrolization process. It consists of a glycerol with three ester
linkages. Overall, anionic surfactants are the most used in household cleaners, often in
conjunction with non-anionic ones, in order to yield even greater stability in solutions.
Some types of surfactants that are used in disinfectants are:
Sodium palmitate
Sodium myristate
Sodium stearate
Note that the main difference between these surfactants is the carbon chain length. The
implications of this will be discussed in greater detail in the next section.
17
Structure-Property Relationships
There are certain characteristics that a disinfectant must possess in order to be
effective. Soiled surfaces, from kitchen counters to bathroom sinks to skin often contain
oily residues. Germs are trapped within these residues, where they are impervious to
washing by water. The presence of organic matter may also impede the disinfectant itself.
Two of the most commonly used disinfecting chemicals are chlorine and glutaraldehyde.
While they have excellent germicidal properties, both are susceptible to inactivation by
organic material (w10). Such organic materials may be part of the “dirt” itself that one is
trying to clean off a surface, or it may be in the form of a biofilm, such as forms inside of
toilets and septic systems.
In order to design an effective disinfectant, one must understand how the
germicide will work in the environment where it will be used. This means that the
interaction between each component of the cleansing agent and the “target” must be
understood. Although the mechanism of germicide action has not been extensively
studied, most scientists hypothesize that the interaction of the chemical agent with the
cell membrane of the microbial species is key. The following an accepted sequence of
events for biocidal activity(19):
(1) adsorption onto cell surface
(2) diffusion through cell wall
(3) binding to the cytoplasmic membrane
(4) disruption of the cytoplasmic membrane
(5) release of cytoplasmic constituents
(6) cell death
18
Taking this as a model for the way common germicides act, we would like to understand
how this mechanism is aided by the addition of colloidal components to disinfectant
solutions.
Glover, et al (7) lists several reasons why surfactants are commonly used in
household disinfectants. These include their ability to penetrate soil, solubilise fatty
materials, wet surfaces, and their contribution to the biocidal action of the disinfectant.
We may split these into two broad categories; one, encompassing the first three properties
above, can be termed surface action, the other, increasing germicidal activity. Although
it has been shown by some research groups that there is actually a relationship between
surface properties and germicidal activity (as will be discussed later), this is a convenient
way to separate the two main characteristics of interest.
Although we have made two distinct categories above, little is actually known
about how colloids, and surfactants in particular, act within cleaning solutions. Chen, et
al, showed that three surfactants commonly used in household products—SDS, Tween 20
and Triton X-100—are effective in the removal of biofilms from surfaces (3). The key to
their research was in studying how biofilms are removed, regardless of whether the
bacteria present within the film were killed. They conclude that biofilm cohesion is
governed by multiple forces, and suggest that the efficacy of surfactants to film removal
might be due to “the disruption of hydrophobic interactions involved in crosslinking the
biofilm matrix”(3). In addition, it was noted that the removal of a biofilm is distinct from
the killing of bacteria.
Chen’s findings are important in that they elucidate one important role a
surfactant can play in cleaning: the presence of organic residue or biofilms may make
19
bacteria impervious to many disinfecting chemicals, but by adding surfactants to these
chemicals the residues can be more easily penetrated or removed altogether.
Glover, et al (7), tackled the other side of the problem by studying how surfactants
affect bacterial cells. They looked at several classes of surfactants—cationic, anionic,
non-ionic and amphoteric—to try and determine how the surfactant structure affects its
interaction with microbes. Their hypothesis stemmed from knowledge about the action
of cationic surfactants. Quaternary ammonium compounds, which are extensively
researched surfactants with known bactericidal effects (7), are cationic. It has been
proposed that they kill cells by changing the permeability of the cell membrane. Starting
from this hypothesis, Glover sought to correlate changes in the cytoplasmic membrane to
the biocidal activity of surfactants.
As expected, it was found that all four types of surfactant increased the fluidity of
the cell membrane by a significant amount. However, they could find no correlation
between this increased fluidity and biocidal activity, which they found varied depending
on the type of organism involved (7). This led them to conclude: “perturbing the fluidity
of the cell membrane is not immediately responsible for cell death.” Therefore, when a
surfactant used in a disinfecting solution greatly increases the bactericidal activity of the
solution it is not necessarily because the surfactant is killing microbes. More likely,
when the surfactant disrupts the membrane of the cell, it makes it vulnerable to the action
of the accompanying disinfectant. This is in agreement with Glover’s conclusion that
amphoteric and non-ionic surfactants, which showed high membrane disruption but little
germicide activity, would show great adjutant ability with disinfectants.
20
In addition to their conclusions about how surfactants disrupt cell function,
Glover et al made an important mechanistic conclusion about how the surfactant disrupts
the cell membrane structure; they proposed that the increase in membrane fluidity was
caused by the surfactant interfering with the packing of the phospholipid hydrocarbons
that form the membrane’s lipid bilayer. This conclusion is supported by Oros, et al (13),
who studied in much greater detail the structure-property relationship governing the
interaction of surfactants with cells.
It is believed that both the length of the polar chain and the type of hydrophobic
group affect the activity of surfactants in cell disruption (13). Oros, et al, sought to
explore this more thoroughly, noting that a large range of activity could be seen in
surfactants even when the hydrophobic group was the same. This would imply that the
chain length was as or more important to cell interaction than the hydrophobic moiety.
They compared surfactants containing polar ethylene oxide chains of varying lengths to
those having none. In their study, they found that the polar chain length was the primary
determinant of biocide activity. For surfactants containing no polar chain, the total length
of the surfactant was smaller than the width of the lipid bilayer in the cell, and any
surfactant reaching the membrane was enveloped with no apparent effect to the cell.
When the chain length was too long, it interacted strongly with water outside the cell and
therefore preferentially stayed in the solvent and did not enter the cell. The only
surfactants capable of effectively disrupting the cell membrane were those containing
ethylene oxide chains of the same length order as the membrane bilayer. These
molecules were readily incorporated into the membrane, where the hydrophobic end
21
interacted with the alkyl chains of the fatty acids while the ethylene oxide chain
interacted with the phospholipid head groups (see figures below).
Figure 7a: Schematic of cell membrane showing lipid bilayer.
Figure 7b: Surfactants with small or no polar tail enter the lipid bilayer and are
contained without affecting membrane function.
Figure 7b: Surfactants with an ethylene oxide tail with length on the order of the bilayer interact
strongly with both polar and hydrophobic groups, resulting in membrane function disruption.
22
Viscardi, et al, studied the properties of some novel cationic surfactants based on
glucose (17). Although the impetus for this study was an interest in environmentally
benign surfactants, they elucidated some important structure-property relationships.
They were able to show a correlation between a surface property of the surfactants,
namely, the critical micelle concentrations (cmc), and the biocidal activity. It was shown
that as the cmc decreases, the ability to kill bacteria increases. Their explanation was that
antibacterial activity is closely related to cell adsorption, and therefore to hydrophobicity.
The more hydrophobic the surfactant, the smaller the cmc, and the more “eagerly” it
attaches to the cell wall of the bacteria.
Another interesting property of glucose-containing surfactants is that by
modifying the number of glucose molecules that are added, one can tune the polarity of
the molecule. This will affect the surface properties by affecting the shape the micelle
can take, which in turn affects how the surfactant interacts with microbes.
The papers cited above have shown how surfactants can be important components
in household cleaning products, as the properties they possess due to their amphiphilic
nature can clearly aid the action of disinfectants.
Disinfectants of the Future: Current Research
As the public becomes more concerned with the environmental fate of widely
used household chemicals, the race is on in industry to find cheap, effective and
environmentally benign disinfecting chemicals. This is one reason knowing the
structure-property relations of all the components in a cleaning solution are so important.
In the case of biocide activity, some important research is currently going on to study
polymers as possible substitutes or modifiers of current disinfecting chemicals. The
main problem with disinfectants, from an ecological standpoint, is that they are lowmolecular weight compounds that are easily find their way into the soil and water supply
23
and readily react to form toxic byproducts. Eknoian, et al, and E.R. Kenawy (18, 19) have
both published papers examining the modification of polymers with active groups that
lend the polymer biocidal action. This has two positive effects: first, the ecological
problem is removed. Polymers can be partially or not at all soluble in water, tend to be
non-volatile, chemically stable compounds and are slow to permeate the skin. Secondly,
they show promise in actually improving biocidal activity. Permanently bound bioactive
groups have been shown to be more effective, and polymers with such modifiers have
application not only in cleaning solutions, but also as coatings to various materials that
will act as a shield to prevent colonization by bacterial species. Some of these advances
are already being seen, one example being the “self-cleaning windows” set to go on the
market this year, which employ a polymer coating and photo-biocatalysis to raise the bar
on the ease and effectiveness of home cleaning.
24
References
1. Behrends, Goroncy, Mohr, and Puchstein, United Stated Patent Application: “Washing
disinfectant for hygienic and surgical hand disinfection.” Serial No. 878283, 2001.
2. Block, Seymour S., Disinfection, Sterilization, and Preservation 5th Ed., Lippincott Williams &
Wilkins, Philadelphia, PA, 2001.
3. Chen, X. and P. S. Stewart, “Biofilm removal caused by chemical treatments” Water Research,
2000 Vol. 34, No. 17, pp. 4229-4233
4. Collins, Allwood, Bloomfield, and Fox, Disinfectants: Their Use and Evaluation of
Effectiveness, Academic Press, 1981.
5. Consumer Reports, July 2000, p. 33-37
6. Felix, Minor, and Sievert, United States Patent Application: “Azeotrope-like compositions
containing fluoroethane.” Serial No. 901239, 2001.
7. Glover, R. E., R. R. Smith, M. V. Jones, S. K. Jackson, C. C. Rowlands, “An EPR
investigation of surfactant action on bacterial membranes” FEMS Microbiology Letters, 1999
pp.57-62
8. E. D. Goddard, Colloids and Surfaces, 1986, 19, 301
9. Kalyon, B D; Olgun, U., American Journal of Infection Control, 2001, 29(2), 124-5
10. Kirk-Othmer, Encyclopedia of Chemical Technology, 3rd Ed., Vol. 7, John Wiley & Sons,
Inc., 1997.
11. T. B. Lindman, Polymer-Surfactant Interactions: Recent Developments in Interactions of
Surfactants with Polymers and Proteins (Chapter 5), ed. E.D. Goddard , 1993
12. I. I. B. Magny, R. Audebert, L. Piculell, B. Lindman, Progress in Colloid and Polymer
Science, 1992, 89, 118.
13. Oros, G, T. Cserhati and E Forgacs, “Inhibitory effect of nonionic surfactants on sunflower
downy mildew. A quantitative structure-activity relationship study” Chemometrics and
intelligent laboratory systems, 1999 Vol 47 pp.149-156
14. Rosenberg, S., Pediatric Infectious Disease Journal, 2000;19(10), S114-6.
15. Spake A., “Losing the battle of the bugs: resistance to antibiotics”, US News and World
Report, May, 1999.8
16. Sun, Y. and Gang, S., Journal of Applied Polymer Science, 2002, v. 84, p. 1592-1599.10
17. Viscardi, G, P. Quagliotto, C. Barolo, P. Savarino, E. Barni and E. Fisicaro, “Synthesis and
Antimicrobial Properties of Novel Cationic Surfactants,” Journal of Organic Chemistry, 2000,
65, 8197-8203.
25
18. Eknonian, M.W., J.H. Putman, and S.D. Worley, “Monomeric and Polymeric H-Halamine
Disinfectants,” Industrial Engineering Chemical Research, 1998, 37, 2873-2877.
19. E. R. Kenawy, “Biologically Active Polymers. IV. Synthesis and Antimicrobial Activity of
Polymers Containing 8-Hydroxyquinoline Moiety,” 2001, Journal of Applied Polymer Science,
Vol. 82, 1364-1374.
Web References:
w1. http://www.epa.gov/oppad001/sciencepolicy.htm
w2. http://ehpnet1.niehs.nih.gov/docs/1995/103-1/focus1.html
w3. http://www.fda.gov/cdrh/ost/reports/fy98/INFECTION.HTM
w4. http://www.messina-oilchem.com/Stimulation/Stimulation-S.html
w5. http://www.ch.kcl.ac.uk/kclchem/staff/arr/abs.htm#Ref_P97
w6. http://jan.ucc.nau.edu/~doetqp-p/courses/env440/env440_2/lectures/lec19/lec19.html
w7. “Biosecurity: Selection and Use of Surface Disinfectants”
www.cdfa.ca.gov
w8. “Clean Smarter, Not Harder”
www.clorox.com/health/cleansmart/cleansmart5.html
w9. www.microcideinc.com/silkyfaq.htm
w10. Biosafety Program, University of Virginia
http://keats.admin.Virginia.edu/bio/disinfectant_summary.html
w11. J. Eliz, “How does chlorine added to drinking water kill bacteria and other harmful
organisms?” Scientific American “Ask the Experts”
www.sciam.com/askexpert/environment/environment22/environment22.html
w12. “Facts About Household Cleaning”
http://www.cleaning101.com/house/fact/houseclean5.html
26
27