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COLLOIDAL SOLUTIONS
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Solutions vs Colloids
The solution - this is a mixture of one or more substances
which are dispersed in solvent (e.g. water).
The true solution is a one phase system because it has
dispersed particles below 1nm:
• particles can not be detected by optical means, like
microscopes, including an ultra microscope.
• solution is homogeneous, as one-phase liquid (e.g. one
solvent or pure water).
• does not show the Brownian movement.
• may pass throug dialitic membrane
10-9 m = 1 nm
= 0.001 micron
10-7 m = 100 nm = 0.1micron
10-6 m = 1000 nm = 1 micron
(Hair diameter 17 to 180 microns )
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Solutions vs Colloids
Solutions:
•
•
•
Transparent to ordinary light
Stable unless solvent evaporated
May pass through dialytic, but not true osmotic,
membranes
10-9 m = 1 nm =
0.001 micron
Colloids:
•
•
•
•
10-7 m = 100 nm =
0.1 micron
10-6 m = 1000 nm = 1 micron
Typically 1-100 nm or more per particle
Not totally transparent – Tyndall Effect
May separate out
Particles are to large to pass through most
membranes
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COLLOIDAL SOLUTIONS
COLLOIDAL SOLUTION – HETEROGENEOUS system with particle size of 10-9-10-7 m in diameter (1 – 100 nm,
up to 500 nm)
10-9 m = 1
nm = 0.001 micron
10-7 m = 100 nm = 0.1 micron
10-6 m = 1000 nm = 1
micron
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The colloidal system [synonyms: colloidal state,
colloid, sol or colloid ] solution –
are heterogeneous dispersive (mostly two phase )
configuration, in which we can distinguish two phases:
• continues - dispersing phase - solvent(s) or bulk
material which is relatively very small in size particles
(e.g. water particles are about 0.1 by 0.2 nm)
• not continues - dispersed phase which particles
diameter are relatively large, 1-100 nm (10-9 – 10–7 m),
and in case of biopolymers – up to 500 nm.
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Properties of colloids:
1. They can be seen in ultra–microscope.
Attention: the difference between an ultra-microscope and
ordinary one is that in the former the light falls laterally on the
liquid under study, instead of “from below”. The ordinary
microscope with x400 magnifications has limitations for
particles below 1 micron, but it is still able to show “general
structures of colloid system”.
2. They are not dialyzed –> Colloidal particles will not be
separated by membranes (like bladder or parchment paper),
because they will not diffuse through a membrane.
3. They show permanent Brownian motions – mostly particles
smaller than 100nm are able to make strong Brownian motion.
4. They show Tyndall effect – visible scattering light by the
colloidal particles.
5. They may coagulate –> colloid particles become agglomerated.
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Types of solutions depending on size of
disspersed phase in dispersive medium
TYPE OF SOLUTION
DIAMETER OF PARTICLES OF
DISPERSED PHASE
True solution
(homogeneous)
< 10-9 m (<1nm)
Colloidal
(heterogeneous)
10-9 - 10-7 m (1-100 nm)
Suspension
> 10-7 m (>100 nm)
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•Colloidal systems are wide spread in nature in organic
or inorganic form.
•All cells in human body are some kind of colloidal
system with different concentration
(proteins, peptides, hydrocarbons, skin,hair)
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Tyndall Effect
This is light scattering by colloidal
example by dust, fog, milk,etc.).
solution
(for
When light beam passes through the colloidal dispersion it
is scatter and therefore is visible.
When light beam passes through the solution, like water,
does not scatter and therefore it can not be seen.
Intensity of this phenomena is larger when difference
between light scattering of dispersive medium is larger
then light scattering of dispersed phase.
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Solutions vs Colloids
The Tyndall Effect
True Solution e.g. water
Colloidal mixture, e.g. milk
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The Tyndall Effect
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CLASSIFICATION OF COLLOIDAL SYSTEMS
DEPENDING ON :
I. STATE OF DISPERSSING AND DISPERSSED PHASE
Disperssed
phase
Disperssing phase
COLLOID
EXAMPLE
Gas
Liquid
Solid
Gas
Gas
Gas
Aerosol liquid
Aerosol solid
Fog, clouds, vapors
Smoke, dust
Gas
Liquid
Liquid
Liquid
Foam
Emulsion
Solid
Liquid
Zol
Foam: soap, beer
Creams, nail polish, milk,
mayonese, butter
Polymer solutions
Gas
Liquid
Solid
Solid
Solid
Solid
Foam
Emulsion solid
Zol solid
Pumice, styrofoam
Gels, opal
Glass rubin, colour cristals
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The most common and important colloidal system are solutions
of liquid in liquid and solid in liquid – called respectively emulsions and sol.
There are following examples of emulsions:
• Water in oil such as cream, butter - they do not conduct
electrical current.
• Oil in water such as milk (colloid of protein and fat in water) –
they conduct electrical current.
Colloids depending on temperature and concentration can exist in
liquid form as a sol, or as a elastic solid - called gel.
• Soles are often transparent and look like true solution.
Dispersed particles are separated from each other by dispersive phase.
• In gels dispersed particles are connected with each other
and create spherical structures in which some of the area is filled
with solvent. This structure gives characteristic “jelly” constituency.
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CLASSIFICATION OF COLLOIDAL SYSTEM
DEPENDS ON:
II. Size of colloidal particles:
monodispersive (particles of dispersed phase have the same
dimensions)
polidyspersive (particles of dispersed phase have the different
dimensions)
III. Ratio of dispersed phase to dispersing medium :
liophilic colloids – they have large affinity to solvent particules;
colloidal particles are serrunded by solvents particles
liophobic colloids – they have small affinity to solvent and
absorb on the particles surface large quantities of one type of
ions
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CLASSIFICATION OF COLLOIDAL SYSTEM
DEPENDS ON (cont.)
IV. Quality of dispersive phase:
Emulsions –
the dispersed phase solutions of nonpolar
substances (e.g. lipids) which do not have affinity with
dispersing phase (e.g. water).
Emulsions have hydrophobic character and are also called
suspenssions or not-reverse colloids.
• In living organisms example of emulssions are lipids.
Small particles of lipids can be dispersed in water thanks to the
compounds called emulsifiers.
Emulsifier – this is compund which can be „dissolved” in both dispersed and dispersing phase.
For example consumed fats are emulsified by bile acids included in bile.
They have ability to decrease surface tension, like soap in water.
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DIFFUSION
COATING
AgI micell structure precipitated with excess of KI
Nuclei of colloidal molecule
+adsorbing layer
core
micell
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COLLOIDS STRUCTURE
Hydrophobic micell are mostly built by oxides,
sulphates, hydroxides of heavy metals
Hydrophilic colloids are built usually from large
molecules such as : proteins.
Their stability are due to the presence of water
molecules adsorbed on their surface.
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Coagulation (1)
COAGULATION – it is ability of colloid particles to combine with
each other and form larger structures called agregates.
After reaching appropriate size they loose ability „to flow” and
they sediment on the bottom.
Coagulation can be caused by:
1.
2.
3.
4.
5.
radioactivity– beta ray
heating – coagulation of protein (egg)
evaporation or freezing of dispersive medium
dehydration, for example by using acetone, alcohol
addition of electrolite to colloid
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Coagulation (2)
Peptization – process reverse to coagulation – breaking
coagulate and return from coagulate to colloid.
SOL
coagulation
GEL
peptization
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Coagulation (3)
Hydrophilic colloid (reversible) – takes place when water coat has
been removed
Hydrophobic colloids (irreversible) – takes palce when electrical
charge present on the surface become neutralized.
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HYDROPHOBIC
COLLOIDS
HYDROPHILIC
Salts with
multivalance cations
coagulate
Water particles
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Coagulation (4)
Conditions for salting out of protein
• Proteins are easiest to be salt out in isoelectric point (pI)
because they do not posses any electrical charge, they attract
themselves the most and they are aggregate which leads to
precipitation. ( no electrical charge helps molecules to join in
aggregates which allows to precipitate from solution).
• In pH different from pI, protein due to charge presence can
exists in solution despite not having water coat
( they behave similar as hydrophobic colloids)
• Addition of small amount of neutralizing electrical charge ions
leads to protein precipitation. Such as protein do not posses
neither electrical charge or water coat.
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Conditions for salting out protein from solution
Protein ion
Protein cation
Protein in pI
Acid addition
pH increase
pH decrease
dyhadration
dyhadration
dyhadration
Base addition
charge lost due
to anion addition
Charge lost due to
cation addition
precipitate
Protein anion
Protein cation
suspenoid
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Salt-out of proteins
• Proteins are easy to salt-out in isoelectric point (pI)
and in this state they easily sediment as a larger aggregates.
[Isoelctric point it is pH at which proteins are amphoteric
and have no electrical charge].
• In pH different than pI protein can exist in solution despite
having no hydrophilic coat.
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Preparation methods of colloidal systems (1)
Colloids preparation
liophilic
Dissolving
liophobic
Dispersion methods
Condensation
methods
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Preparation methods of colloidal systems (2)
Dispersion methods
Size reduction until obtaining colloids by:
mechanical means (colloidal mill)
electrical means – to obtain sole of metals, metal oxides, etc.
ultrasounds (20000Hz) to obtain e.g. dyes, gypsum.
In this group is also peptization. This tools are separating combined colloidal
molecules.
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Preparation methods of colloidal
systems (3)
Condensation methods
Colloid’s size reduction is obtain by addition of particular chemical
molecules. There are following methods to obtain it:
polymerization
decreasing in solubility (e.g.: receiving of colloidal solution of sulphur
in water by pouring saturated solution if sulphur in alcohol into water)
reduction (e.g. nobel metal ions)
oxidation
ion exchange (e.g.: AgNO3 + KI AgI + KNO3)
hydrolysis (e.g.: metal hydroxyls)
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PROTECTIVE ROLE OF HYDRPHILIC COLLOIDS
ON HYDROPHOBIC COLLOIDS
Hydrophilic colloids show higher stability than hydrophobic colloids,
because of two stabilizing factors:
hydration layer
sometimes particles have the same charge (which can be result of dissotiation of
acidic or basic groups being present in colloidal particle)
Hydrophilic colloids are acting protective on hydrophobic colloids – addition of
hydrophilic colloid to hydrophobic is causing creation of stable system from which it is
difficult to precipitae suspended particles (e.g. small amount of protein added to colloidal
gold suspension are protecting it from coagulation).
Protective role of colliod can be determined quantitatively by providing gold number
( gold number it is the smallest amount of miligrams of protective colloid in respect to
pure substance which is able to protect 10cm3 0,1% of formaldehyde gold zol, against
color change from red to purple after addition 1cm3 10% NaCl )
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Colloids in fluid therapy (1)
Fluid therapy
(1):
treatment consisting of fluid intake (usually intravenous, intraarterial or
subcutaneous)
often used to treat both hospital and emergency
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Colloids in fluid therapy (2)
Fluid therapy
(2):
leveling fluid deficiency is one of the most urgent tasks in the treatment of
critically ill patients with hypovolemia
hypovolemia
-a
decrease in intravascular volume, resulting in insufficient functioning of the
normal mechanisms to hold fluid in the bearing
- may exists as a reduced, normal or increased extracellular volume
- large
hypovolemia is leading to hypovolemic shock
Keeping adequate fluid therapy contributes to the reduction of organ
disfunction and shortens hospitalization.
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Colloids in fluid therapy (3)
Basic conditions requiring fluid therapy :
all forms of shock (usually hypovolemic shock, but also anaphylactic
shock, septic, neurogenic)
dehydration due to increased fluid loss (diarrhea, vomiting)
burns (increase in vascular permeability in the case of burns results
in the loss of fluid to the patient)
deficiency states of other body fluids
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Colloids in fluid therapy (4)
The objectives of conducting fluid therapy :
replenishment of electrolytes and nutrients
replenishing fluids (eg. blood lost as a result of hemorrhage)
supply of drugs in combination with liquid (when the medication
should be administered for several minutes or at high dilution)
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Colloids in fluid therapy (5)
Fluids used for fluid therapy :
Crystalloids (aqueous solutions of electrolytes or glucose, such as
0.9% NaCl, 5% glucose solution, Ringer's solution, polyelectrolitic
isotonic fluid "PWE")
- used for blood loss up to 15% of body weight
indicated in patients who have a deficiency of fluid in the interstitial
space or patients with immunodeficiency electrolyte (burned and
dehydrated)
-
Colloidal solutions (natural and synthetic )
- used
for blood loss exceeding 15% of body weight
- indicated
in situations where there is insufficient supply of crystalloid or
are contraindication for their use (eg. risk of pulmonary edema)
-it
is estimated that administration of 1 liter of colloidal solution
corresponds to the administration of 4 liters of crystalloid
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Colloids in fluid therapy (5) cont.
Blood and blood-related products :
- packed red cells, (RBC, pRBC, PRBC),
- fresh frozen plasma (FFP),
- blood plates concentrate
http://reference.medscape.com/drug/ffp-octaplas-fresh-frozen-plasma-999499
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Colloids in fluid therapy (6)
Colloidal solutions
synthetic
natural
gelatines
- made of collagen obtained
of tendons, skin and bones
- Small molecular weight - 35 kDa
(fast urinary excretion )
- short-term volume effect
Human albumin
- works for 24–36 h,
- reraly cuases allergic reaction
- big quantities may cause coagulopathy
- used in:
severe protein deficiency states ,
extensive burns,
brain edema
ascites
expensive
- A minimal effect on hemostasis
starch hydroxyl (HAES/HES)
-Synthethised from amylopectine
-- HES: Plasmasteril (6% HES 450/0.7) and 3%,
6%, 10% solutions HES:,
HES 200/0.5, HES 200/0.5, HES 130/0.4
- prefered:
show beneficial rheological effect and inhibition of
blood plates aggregation
does not accumulate in plasma and tissues and does
not affect hemostasis and renal function
dextran
- polymers consisting of 200-450 glucose molecules
- have been used in the clinic :
6% i 10% dextran solution 40 (T1/2= 2-3 h)
6% dextran solution 70 (T1/2= 6-8h)
- used to supplement intracellular volume by improving
reological properties of blood, in anticoagulant therapy
- Amoung colloids are the most often causing anaphylactic
reactions
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Colloids in fluid therapy (7)
Colloidal solutions - advantages :
allow for faster replenishment of intravascular space (hemorrhage,
shock)
compared to crystalloids provide faster, stronger and longer-lasting
volume effect
- are causing oncotic pressure increase, which leads to the movement of water into the vessel
- remain
-
long in the intravascular compartment (2-12
hours)
after administration of colloids an increase in intravascular volume is observed –
from 100 % to up to 400%
have a positive impact on hemodynamics, organ perfusion and oxygen
supply
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Colloids in fluid therapy (8)
Colloidal solutions -disadvantages :
can cause allergic reactions
after the administration of large amounts may occur :
- dilution
effect of blood components: proteins, coagulation factors
- decreases
in hematocrit concentration
price
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Colloids in fluid therapy (9)
Ideal colloidal solution:
should not accumulate in the plasma and tissues,
but readily undergo elimination from the body
HES 130/0,4
should not affect hemostasis and renal function
should be suspended in crystaloid solution to avoid dehydration of
extracellular space and impairment of kidney functions
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The End
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