Detergents and Surfactants.docx

7/28/2019 Detergents and Surfactants.docx

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Detergents and SurfactantsIntroduction:

Synthetic detergents have similar

molecular structures and properties assoap. Although the cleansing action issimilar, the detergents do not react as

readily with hard water ions of calcium

and magnesium. There are over athousand synthetic detergents available

in the United States. Detergent

molecular structures consist of a long

hydrocarbon chain and a water solubleionic group. Most detergents have a

negative ionic group and are called

anionic detergents. The majority are alkysulfates. Others are "surfactants" (from

surface active agents) which are

generally known as alkyl benzene

sulfonates.

Quiz: Whic

h part of themolecule is

soluble in

water?

Answ er

Which partof the

molecule is

insoluble inwater?

Answ er

Which part

of the

molecule isinteracts

with dirt or

oil?

Answ er


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Cationic Detergents:

Another class of detergents have a positive

ionic charge and are called "cationic"

detergents. In addition to being good

cleansing agents, they also possessgermicidal properties which makes them

useful in hospitals. Most of thesedetergents are derivatives of ammonia.

A cationic detergent is most likely to befound in a shampoo or clothes "rinse". The

purpose is to neutralize the static electrical

charges from residual anionic (negative

ions) detergent molecules. Since thenegative charges repel each other, the

positive cationic detergent neutralizes thischarge.

It may be surprising that it even works

because the ammonium (+1) nitrogen isburied under the methyl groups as can be

seen in the space filling model.

Neutral or non-ionic detergents:

Nonionic detergents are used in dish

washing liquids. Since the detergent doesnot have any ionic groups, it does notreact with hard water ions. In addition,

nonionic detergents foam less than ionic

detergents. The detergent molecules musthave some polar parts to provide the

necessary water solubility.

In the graphic on the left, the polar part

of the molecule consists of three alcoholgroups and an ester group. The non-polarpart is the usual long hydrocarbon chain.


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Detergent Properties and ApplicationsBy: Vicki Caligur, BioFiles 2008, 3.3, 14.

The key to detergent function is an amphipathic structure. All detergents are characterized as containinga hydrophilic head region and a hydrophobic tail region (seeFigure 1).

Figure 1. Structure of the anionic detergent sodium dodecyl sulfate (SDS), showing the hydrophilic andhydrophobic regions.

These structural characteristics allow detergents to aggregate in aqueous media. At a sufficiently highconcentration, the polar hydrophilic region of each molecule is oriented toward the polar solute (water)while the hydrophobic regions are grouped together to form thermodynamically stable micelles withhydrophobic cores. The hydrophobic core region of the detergent micelle associates with the hydrophobicsurfaces of proteins and results in soluble protein-detergent complexes. Figure 2 is a simple illustration of


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a micelle to demonstrate the orientation concept. Actual micelle structures are more complex anddynamic, and can change due to detergent concentration and solution composition.1

Figure 2. Simple illustration of a sodium dodecyl sulfate micelle.

Biological detergents are commonly used to disrupt the bipolar lipid membrane of cells in order to releaseand solubilize membrane-bound proteins. Some detergents can be used to solubilize recombinantproteins, while others are recommended for the stabilization, crystallization, or denaturation of proteins.Detergents can align at aqueous/non-aqueous interfaces, resulting in reduced surface tension, increasedmiscibility, and stabilization of emulsions. Additional detergent applications include:

Extraction of DNA and RNA

Solubilization of specimens for diagnostic applications

Cell lysis

Liposome preparation

Prevention of reagent and analyte precipitation from solution

Prevention of non-specific binding in immunoassays

Detergent Physical Characteristics

The concentration at which micelles begin to form is the critical micelle concentration (CMC). The CMCis the maximum monomer concentration and constitutes a measure of the free energy of micelleformation. The lower the CMC, the more stable the micelle and the more slowly molecules areincorporated into or removed from the micelle. The structure of the hydrophobic region of the detergentcan affect the micelle structure. An increase in the length of the hydrophobic hydrocarbon chain of ionic
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detergents results in an increased micelle size and a lower CMC, as fewer molecules are needed toconstruct a micelle.

The average number of monomers in a micelle is the aggregation number. The CMC and aggregationnumber values are highly dependent on factors such as temperature, pH, ionic strength, and detergenthomogeneity and purity. Slight discrepancies in reported values for CMC and aggregation number maybe the result of variations in the analytical methods used to determine the values. Aggregation number

values are also shifted by concentration, since the number of detergent molecules per micelle mayincrease if the concentration is above the CMC.

Ease of removal or exchange is an important factor in the selection of a detergent. Some of the morecommon detergent removal methods include:

Dialysis

Gel filtration chromatography

Hydrophobic adsorption chromatography

Protein precipitation

The CMC value associated with the detergent is a useful guide to hydrophobic binding strength.Detergents with higher CMC values have weaker binding and are subsequently easier to remove bydialysis or displacement methods. Detergents with low CMC values require less detergent in order to formmicelles and solubilize proteins or lipids.

Another useful parameter when evaluating detergents for downstream removal is the micelle molecularweight, which indicates relative micelle size. Smaller micelles are more easily removed and are usuallydesirable when protein-detergent complexes are to be separated based on the molecular size of theprotein. The micelle molecular weight may be calculated by multiplying the aggregation number by themonomer molecular weight.

The cloud point is the temperature at which the detergent solution near or above its CMC separates intotwo phases. The micelles aggregate, typically forming a cloudy phase with high detergent concentration,while the balance of the solution becomes detergent-depleted. The resulting two-phase solution can be

separated, with the extracted protein being located in the detergent-rich phase. Detergents with low cloudpoint temperatures, such as TRITON X-114 (cloud point ~23 C) are recommended for use with proteinssince high cloud point temperatures may denature solubilized proteins. The cloud point can be affectedby changes in detergent concentration, temperature, and the addition of salt or polymers such as dextranand polyethylene glycol. Note that the detergent-rich phase is also contingent on the specific detergent(s)and salt concentration; under some conditions the phase may be clear rather than cloudy and be locatedas either the upper or lower phase of the solution. In non-ionic detergents, this behavior has been appliedin the phase separation and purification of membrane proteins.2

Detergent Types and Selection

When selecting a detergent, the first consideration is usually the form of the hydrophilic group:

Anionic

Cationic

Non-ionic

Zwitterionic (ampholytic)
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Anionic and cationic detergentsare considered biologically harsh detergents because they typicallymodify protein structure to a greater extent than neutrally charged detergents. The degree of denaturationvaries with the individual protein and the particular detergent and concentration. Ionic detergents aremore sensitive to pH, ionic strength, and the nature of the counter ion, and can interfere with downstreamcharge-based analytical methods.

Non-ionic detergentsare considered to be mild detergents because they are less likely th an ionic

detergents to denature proteins. By not separating protein-protein bonds, non-ionic detergents allow theprotein to retain its native structure and functionality, although detergents with shorter hydrophobic chainlengths are more likely to cause protein deactivation. Many nonionic detergents can be classified intothree structure types:

Poly(oxyethylene) ethers and related polymers

Bile salts

Glycosidic detergents

Poly(oxyethylene) ethers and related detergents have a neutral, polar head and hydrophobic tails that areoxyethylene polymers (e.g. Brij and TWEEN) or ethyleneglycoether polymers (e.g. TRITON). The tert-

octylphenol poly(ethyleneglycoether) series of detergents, which includes TRITON X-100 andIGEPAL CA-630, have an aromatic head that interferes with downstream UV analysis techniques.

Bile salts have a steroid core structure with a polar and apolar orientation, rather than the more obviousnonpolar tail structure of other detergents. Bile salts may be less denaturing than linear chain detergentswith the same polar head group.

Glycosidic detergents have a carbohydrate, typically glucose or maltose, as the polar head and an alkylchain length of 7-14 carbons as the polar tail.

Zwitterionic detergents have characteristics of both ionic and non-ionic detergent types. Zwitterionicdetergents are less denaturing than ionic detergents and have a net neutral charge, similar to non-ionicdetergents. They are more efficient than non-ionic detergents at disrupting protein-protein bonds andreducing aggregation. These properties have been used for chromatography, mass spectrometry, and

electrophoresis methods, and solubilization of organelles and inclusion bodies.Non-detergent sulfobetaines (NDSB), although not detergents, possess hydrophilic groups similar tothose of zwitterionic detergents but with shorter hydrophobic chains. Sulfobetaines do not form micelles.They have been reported to improve the yield of membrane proteins when used with detergents andprevent aggregation of denatured proteins.

DETERGENTS

DEFINITION www.citycollegiate.comDetergents are soap-like compounds which are used for cleaning purpose. They are

sodium salts of long chain alkyl benzene sulphonic acids or sodium salts of long chain

alkyl hydrogen sulphate, whereas, soaps are sodium salts of long chain carboxylic

acids. The general formulae of soaps and detergents are:


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Detergents may be used in hard water without the formation of scum. This is the

advantage of a detergent over soap which gives curdles when used with hard water.STRUCTURE OF

DETERGENTS www.citycollegiate.com

A detergent consists of two parts:

Hydrophilic part (water soluble)

Hydrophobic part (oil soluble)Hydrophilic partHydrophilic part is sodium salt which is readily soluble in water. e.g. SO3

-,OSO3

-,OH- or NR4.

This part of a detergent is ionic and is attracted by polar water molecules.Hydrophobic part

hydrocarbon part of detergent is called hydrophobic part. It is non-polar .

Hydrophobic part is insoluble in water but it is soluble in oil.This part consists of ahydrocarbon segment and can dissolve oil or grease.

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:www.citycollegiate.comCLEANING ACTION

When a greasy cloth is put into aqueous solution of a detergent, The hydrophilic partof detergent is dissolved in water while hydrophobic part dissolves grease or oil like

substances on the cloth. On slight agitation grease is readily removed from the cloth.ADVANTAGE OF

DETERGENT www.citycollegiate.com

See difference between soap and detergent.DISADVANTAGE OF

DETERGENTHydrocarbon chain of detergent does not broken by bacteria and bacteria remain in

the solution.DIFFERENCE BETWEEN SOAP AND DETERGENT

SOAP DETERGENT

Soaps are sodium salts of longchain carboxylic acids.

Detergents are sodium salts of longchain alkyl benzene sulphonic acids or

alkyl sulphate.

It is obtained by natural resources

i.e. fats and oils.Detergents are synthetic materials.

Calcium and magnesium salts ofsoaps are insoluble in water.

Calcium and magnesium salts ofdetergents are soluble in water.

In hard water it produces scumwhich affect its cleaning action.

Hard water does not affect its cleaningaction.

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Properties
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Nonionic detergents, which form electrically neutral colloidal particles in solution, contain non-ionic

emulsifiers, amplifying the ability to remove oily residues. These nonionic surfactants are low-foaming and

have defoaming properties that improve wetting, rinsing and particle removal while not hindering with

mechanical labor. A common nonionic detergent is Liquinox used to clean glassware and does not react

with hard water ions; this is due to the fact that no ionic groups exist to do so. In addition, it foams less

than ionic detergents but has some polar portions to provide necessary water solubility.

Cationic detergents often come in powder foam and have a long cationic chain that is responsible for

surfactant properties. However, cationic detergents are poor detergents even though they have adequate

emulsifying properties. Instead, there are often used in bacterica/germ free environments due to their

antiseptic properties.

Anionic detergents are based on sulfate or carboxylate anions and are of the most common modern

synthetic detergents producing negative charged colloidal ions in solution.

Bile salts in the stomach have emulsifying properties in the digestive system, reacting with fats and oils

as a detergent to form smaller particles of the consumed compounds. In addition, the same amphipathicproperties that allow bile acids to emulsify using lipids also make them membrane-disruptive mediums.

The structure of detergent

For soapy detergent: the ionic head should be

For soapless detergent: the ionic head may be


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DetergentsTechnical Centre

Technical Support

Detergents are chemicals designed to assist in the removal of soil from a surface and are available as powders,

liquids, foams or gels. Detergents have two modes of action (physical & chemical) depending on their makeup and

the soil they are acting upon.

When selecting a detergent, the following points should be considered:

Type of soil to be removed

Cleaning method required

Cleaning equipment available

Will disinfection be required Time window

Water hardness

Chemical concentration required

Water temperature

Materials of construction

Operator safety

Risk to food safety

Cost


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Detergent Components

Surfactants (Surface Active Agents) are an important part of any detergent as they enable the detergent to

increase the wetting power of water by reducing its surface tension. This ability increases the contact between

the soil and the detergent solution and allows it to penetrate the minute irregularities of the dirt more effectively.

Four types of surfactants are available, which are:

Anionic - the active part is negatively charged and generally is a good foamer and has good wetting properties.

Cationic - the active part is positively charged and generally is biocidal.

Amphoteric - which is cationic in acid medium and anionic in alkaline medium. Can sometimes be biocidal.

Non-ionic surfactant, these have no overall charge but are very good emulsifying agents.

Sequestrants counteract the effect of water hardness salts, preventing the formation of scale drop out. Scale drop

out on surfaces provides a barrier to cleaning and a place where microbes can reside and grow.

Sequestrants bind the calcium/magnesium ions in the hard water to form soluble complexes and thereby prevent

scale formation. The level of sequestrant in the detergent and the detergent concentration must be matched to

the water hardness and mineral salts that may be present in the soil to be removed.

The base of a detergent will determine what type of detergent it is alkaline, acid or neutral. For example in an

alkaline detergent, the base is usually caustic soda (sodium hydroxide).

In some cases, the detergent may have a chlorine donor that is added to assist in protein and stain removal. The

chlorine donor is there primarily for this purpose and not as a biocide.

Inhibitors are sometimes added to detergents to reduce the attack on the metal surface (for instance inhibitors

added to hydrochloric acid formulations - Descaler). Alternatively, the formulation may be designed to prevent

attack on soft metals such as aluminium, tin and brass (Silicated alkaline products - Chlorfoam 2000).

Alkaline and Caustic detergents are probably the most common detergents used throughout the food industry as

they have good fat and protein removal properties and they can be used across a wide spectrum of food

manufacturing environments. Both contain sodium hydroxide boosted with surfactants and sequestrants. Caustic

detergents contain higher levels of Sodium Hydroxide and generally have higher risk classifications than alkaline

detergents. They are corrosive to skin and should always be used in conjunction with the correct PersonalProtective Equipment. They may also attack soft metals such as aluminium, tin, brass etc.

Acid Detergents

These are used mainly for protein, mineral and vegetable deposit removal and typically contain phosphoric acid.

Acids must never be allowed to come into contact with chlorine compounds because of the consequential release

of chlorine gas, which can prove to be fatal.

Neutral Detergents

These are generally blends of surfactants used for manual dishwashing and manual cleaning. They are generally

safe to use and are found predominantly in domestic and light industrial use. Gloves should still be worn to avoid

de-fatting of the skin and to reduce the risk of dermatitis.

Types of Soil

There are essentially two types of soil:

Organic These are derived from living matter and include animal fat, vegetable oils, starch, sugars, and proteins

from milk, egg, meat or blood. Normally they can be removed by using neutral or alkaline detergents, but if

heated, dried or allowed to remain for a prolonged period then caustic detergents may be required to remove

them.


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When removing liquid protein deposits such as egg, blood or meat it is best practice to begin with a cold water

rinse first to prevent cooking of the protein.

When grease or oil is heated it will form a resolute, dark, sticky polymerised deposit, which can generally be

removed with an alkaline detergent. If the polymerised deposit is heated further it results in the formation of

carbon, which generally has to be removed by a more aggressive caustic alkali detergent such as sodium

hydroxide.

Inorganic These include water hardness salts (scale), oxidised metals (rust), uric acid salts (urinal stains),

beerstone and calcium salts deposited from milk (milkstone). These types of soils are usually removed with acids

such as hydrochloric and phosphoric.

Soils are very rarely made up of one component, for example a hard scale in a meat processing area may be a

complex of a mineral scale and protein.

Water Chemistry

All water used for domestic and industrial purposes will have hard water salts (calcium and magnesium ions)

present.

Water hardness is a measurement of the level of these dissolved solids in the water. These solids may come out of

solution and precipitate as a scale under certain conditions; namely:

An increase in water temperature highest effect as water is raised to boiling point.

As the pH of water is increased; e.g. by adding an alkaline detergent.

The level of hard water salts varies from area to area in the UK, for example, water used in some areas of the north

of Scotland will have less than 60ppm (parts per million as CaCO3) hard water salts because the water is generally

surface water held in reservoirs and has not passed through limestone deposits. In areas such as the South East

where the underlying rock is limestone, water hardness can easily be over 600ppm.

1. Alkaline Detergents

It is the main detergent ingredient, able to combine with fats and oils toform soap and dissolves proteins which can be remove by water. Howeverit is corrosive due to its high level of active alkalinity and it is harmful to thehuman body as alkaline dissolves the phospholipid layers on our body.Hence, Alkalinity, corrosiveness, effectiveness in cleaning. Alkaline

detergents are also commonly use in food processing and food serviceindustries. General household detergents are home-grade detergents withmild level of alkaline that is able to remove fresh soil from floors, walls,ceilings, preparation surfaces, most equipment and utensils. Highly alkalinecleaners (Heavy-duty detergents) that remove wax, aged or dried soil, andbaked-on grease.


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Examples of alkaline detergents

Sodium Hydroxide (NaOH):Known as caustic soda/ lyeStrongest and cheapest alkalineCapable of dissolving protein and turn fat to soapPrecipitate calcium and magnesium in waterUsually use to remove heavy soilsNot suitable for certain meta equipments.

(E.g. Aluminium as NaOH will cause these metals to be integrated into thefood)

Hard to remove by rinsingHighly corrosive on all surfaces (including skin)Wetting agents (Emulsifiers) can be added to improve rinsing properties

while preventing its corrosive abilities

Sodium Metasilicate:Less corrosive and effectiveness than NaOHSafer to handleTo prevent soil detergent mixture from precipitating should be used at water

temp. >62oC

Good rinsing and wetting properties

Sodium Carbonate:Mild alkalisAct as a buffering agentLess effective than NaOH and sodium MetasilicateNon-corrosiveSafe to handleRarely use in industriesUsed for cleaning hands

2. Acid Detergents


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It involves acid as the major component which is used in dissolving mineraldeposits (Calcium and Magnesium precipitates) or hard water depositsfrom equipment surfaces. Removing mineral deposits effectively with aciddetergents as compared to alkaline detergents or other cleaners. Two maingroups of acid detergents: Inorganic (HCL, H

2SO

4) , Organic (Vinegar,

Citric Acid).

Examples of acid detergents

1. Inorganic Acids:Known as mineral acids/ strong acidsExamples: Hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid

(Highly corrosive)Excellent for removing and controlling mineral deposits, rust, alkalineIrritation to skin and extremely corrosive2. Organic Acids:Milder acid than inorganicExamples: Citric, Tartaric( Found in Grapes)Less corrosive to metalsLess irritation to skin as compare to inorganic acids

3. DegreasersConsists surfactants (complex molecule, reduces the surface tension ofwater when added to water to allow closer contact between the soil depositand the cleaning medium). It is use for removing grease and greasy soiland able to penetrate and hydrolyze fats and oils into smaller particles tobe then removed by water.

4. Abrasive Detergents

It is a powder or paste than contains abrasives like pumice, quartz or sand.Abrasive is usually ground into small particles size and is use on equipmentsurfaces that requires scrubbing, scouring or polishing. However, it cancause scratches on metal surfaces and it needs to be washed awaycompletely to prevent contamination of food.


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5. Detergent Sanitizers

Detergent Sanitizers contain a sanitizer/ disinfectants with a detergent and

it cleans and sanitize in one operation which saves time and labour as well.It also function as a detergent for heavy soil and sensitive areas. There are3 major types of detergent sanitizers:

- - Alkaline detergents + Hypochlorite (Assist in removing protein residues) - - Alkaline Detergents (Not containing an anionic surfactant) + Quaternary

Ammonium Coumpound- - Acid Detergent + iodophor (iodine- containing material)

How to choose the most suitabledetergents?

- - Type of soil to be removed- - Type of material to be clean so that the detergent does not damage it - - Type of cleaning technique

- Manual Labour, do not use excessive acid or alkaline

detergents

Detergents

Detergent is a material that helps in cleaning. Detergent contains one of more surfactants which are

capable of reducing the surface tension of liquid such as water. Commonly, detergent consists of long

chain hydrocarbon and ionic group (such as alky sulfate or derivative of ammoniac group).

[edit]Types of Detergents

Anionic

These detergents are man-made and consist of long hydrocarbon chains and a water-soluble ionic group,

which is usually negatively charged. These detergents are commonly known as surfactants, or alkyl

benzene sulfonates

Cationic
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These detergents are also man-made, and they only differ from anionic detergents in that the water-

soluble ionic group is positively charged. These detergents are primarily derivatives of ammonium and

are commonly used as a germicide and in shampoo.

Neutral

These type of detergents contain the same general set up as all other detergents, except its overallcharge is neutral. The head of the detergent is polar due to the presence of three hydroxyl groups and an

ester group.

Natural

Natural detergents such as bile salts (sodiumglycoholate) are made in the liver. These detergents are

derivatives of cholesterol, a type of lipid. Its main function is digestion. The bile salt is capable of

emulsifying fats and oils such that enzymes may break them down further.

[edit]Function and Application
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Detergents and Surfactants.docx