1

COLLOIDAL SOLUTIONS

Department of Medical Chemistry

Pomeranian Medical University

2

COMPONENTS OF THE SYSTEM -chemicals which create the system.They create different type of mixtures - which makes the system toexists in various phases.

PHASE – part of the system is separated from other phases withdistinct border where sudden change in physico-chemical changestakes place.• Phase containing one component – pure substance• Phase containing more than one component - solution

SOLUTION – mixture of two or more components dissolved in

solvent (solvent-subtance in quantitative excess over other

componet)

3

HETEROGENOUS –multiplephase (seemingly single-phase),

heterogeneous; eg. water with ice (heterogeneous, two-phase, single-

component system ), water with mercury (heterogeneous, two-phase, two-

component system )

HOMOGENOUS –single-phase, homogeneous throughout the volume,

both chemically and physically; e.g. glucose solution (homogeneous

single phase, two components system)

Systems can be divided due to:

1) number of components: ➢ one-component

➢ multicomponent

2) number of phases :➢ single phase

➢ multiple phase

SYSTEMS:

SYSTEMS

4

Types of solutions depending on size of

dispersed 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)

5

in animate nature (proteins, carbohydrates)

in inanimate nature (clay, fog, volcanic dust)

COLLOIDAL SOLUTIONS – heterogenous dispersive system withdistinguished continuous scattering phase (solvent) and discontinuous dispersed phase with particle diameter of 10-9 - 10-7 m (1 – 100 nm, up to 500nm)

Colloidal systems are widespread :

COLLOIDAL SOLUTIONS

synthetic materials (soap, colorants, colloidal sulphur, metal oxides)

All living cells are sets of various colloidal systems.

6

COLLOIDAL SOLUTION – HETEROGENEOUS system -

with particle size of 10-9-10-7m in diameter (1 – 100 nm,

up to 500 nm)

COLLOIDAL SOLUTIONS

10-9 m = 1 nm = 0.001 micron10-7 m = 100 nm = 0.1 micron10-6 m = 1000 nm = 1 micron

7

Properties of colloids (1):

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 do strong Brownian motion.

4. They show Tyndall effect – visible light scattering by the

colloidal particles.

5. They may coagulate –> colloid particles become agglomerated.

8

Tyndall Effect

This is light scattering by colloidal solution (forexample by dust, fog, milk,etc.).

When light beam passes through the colloidal dispersion itis scattered and therefore is visible.

When light beam passes through the solution, like water,it is not scatter and therefore it cannot be seen.

Intensity of this phenomena is larger when differencebetween light scattering of dispersive medium is largerthen light scattering of dispersed phase.

9

Solutions vs Colloids

Colloidal mixture, e.g. milkTrue Solution e.g. water

The Tyndall Effect

10

The Tyndall Effect

11

CLASSIFICATION OF COLLOIDAL SYSTEMS

DEPENDING ON :

I. STATE OF DISPERSING AND DISPERSED PHASE

Disperssed

phase

Disperssing phase COLLOID EXAMPLE

Gas

Liquid

Solid

Gas

Gas

Gas

-

Aerosol liquid

Aerosol solid

-

Fog, clouds, vapors

Smoke, dust

Gas

Liquid

Solid

Liquid

Liquid

Liquid

Foam

Emulsion

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

12

CLASSIFICATION OF COLLOIDAL SYSTEM :

Size of colloidal particles:

➢monodispersive (particles of dispersed phase have the same dimensions)

➢ polydispersive (particles of dispersed phase have different

dimensions)

Affinity of dispersed phase to dispersing medium :

•liophilic colloids – they have large affinity to solvent particles;colloidal particles are surrounded by solvent particles

• liophobic colloids – they have small affinity to solvent andadsorb on the surface of particles large quantities of one typeof ions

II.

III.

13

CLASSIFICATION OF COLLOIDAL SYSTEM

DEPENDS ON (cont.)

IV. Quality of dispersed phase:

Emulsions – the dispersed phase is of nonpolar character(e.g. lipids) and does not have affinity to dispersion medium(e.g. water).

Emulsions have hydrophobic character and are also calledsuspensions or irreversible colloids.

• In living organisms example of emulssions are lipids.

Small particles of lipids can be dispersed in water thanks to thecompounds called emulsifiers.

Emulsifier – this is compund which can be „dissolved” in both –dispersed phase and dispersion medium.

For example, consumed fats are emulsified by bile acids contained in bile.

They have ability to decrease surface tension, like soap in water.

14

AgI micelle structure precipitated with excess

of KI

micelle

core

Nucleus of colloidal molecule

+adsorbtion layer

DIF

FU

SIO

N L

AY

ER

nucleus

15

COLLOIDS STRUCTURE

Hydrophobic micell are mostly built by oxides,sulphates, hydroxides of heavy metals

Hydrophilic colloids are built usually by largemolecules such as : proteins.Their stability is due to the presence of watermolecules adsorbed on their surface.

16

Coagulation (1)

COAGULATION – it is an 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.

1. radioactivity– beta ray2. heating – coagulation of protein (egg)3. evaporation or freezing of dispersive medium4. dehydration, for example by using acetone, alcohol5. addition of electrolite to colloid

Coagulation can be caused by:

17

Coagulation (2)

Peptization – process opposite to coagulation – breakingcoagulate and return from coagulate to colloid.

SOL coagulation GEL

peptization

18

Coagulation (3)

Hydrophilic colloid (reversible) – takes place when water coathas been removed

Hydrophobic colloids (irreversible) – takes palce when electricalcharge present on the surface becomes neutralized.

19

COLLOIDSHYDROPHOBIC HYDROPHILIC

Salts with

multivalance cations

coagulate

Water particles

Strongly hydrated salts

20

Coagulation (4)

Conditions for salting out of protein

• Proteins are easiest to be salted out in their isoelectric point(pI) because they do not posses any electrical charge, they attractthemselves strongly and create aggregates, which leads toprecipitation (lack of electrical charge helps molecules toaggregate, which allows them to precipitate from solution).

• In pH different from pI, protein due to presence of the surfacecharge can exist in solution despite not having water coat( they behave similar as hydrophobic colloids)

• Addition of small amount of neutralizing electrical charge ionsleads to protein precipitation. Such protein does not posses eitherelectrical charge or water coat.

21

Conditions for salting out protein from solution

Protein ionProtein in pI

Protein cation

Acid addition

Charge lost due to

cation addition

dyhadra

tion

precipitate

Protein anionProtein cation

suspenoid

Base addition

pH decreasepH increase

charge lost due

to anion addition

22

Salting out of proteins

• Proteins are easy to salt-out in isoelectric point (pI)

and in this state they easily sediment as larger aggregates.

[Isoelctric point it is pH at which proteins have no electrical charge].

• In pH different than pI protein can exist in solution despite having no hydrophilic coat.

http://elte.prompt.hu/sites/default/files/tananyagok/IntroductionToPracticalBiochemistry/ch05s04.

html

23

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 ofdissotiation 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 protects it from coagulation).

Protective role of colloid can be determined quantitatively by providing goldnumber

( gold number it is the smallest amount of miligrams of protective colloid inrespect to pure substance which is able to protect 10cm3 0,1% offormaldehyde gold zol, against color change from red to purple after additionof 1cm3 10% NaCl )

24

Colloids in fluid therapy (1)

Fluid therapy (1):

treatment consisting of fluid intake (usually intravenous, intraarterial or

subcutaneous)

often used in hospital as well as emergency

25

Colloids in fluid therapy (2)

Fluid therapy (2):

compensating 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 vascular bed

- may exists as a reduced, normal or increased extracellular volume

- large hypovolemia leads to hypovolemic shock

Keeping adequate fluid therapy contributes to the reduction of organ

disfunction and shortens hospitalization time.

26

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 case of burns results in

the loss of fluid)

other fluid deficiency states

27

Colloids in fluid therapy (4)

The objectives of conducting fluid therapy :

replenishment of electrolytes and nutrients

replenishing fluids (ex. 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)

28

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")

Colloidal solutions (natural and synthetic )

- used for blood loss up to 15% of body weight

- used for blood loss exceeding 15% of body weight

- indicated in case of patients who have deficiency of fluid in the

interstitial space or patients with deficiency of electrolytes (burned and

dehydrated)

- indicated in situations when supply of crystalloid is insufficient or there

are contraindications 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

29

Blood and blood-related products :

- packed red cells, (RBC, pRBC, PRBC),

- fresh frozen plasma (FFP),

- blood plates concentrate

Colloids in fluid therapy (5) cont.

http://reference.medscape.com/drug/ffp-octaplas-fresh-frozen-plasma-999499

30

Human albumin- has an effect for 24–36 h,

- reraly causes allergic reaction

- big quantities may cause coagulopathy

- used in:

✓ severe protein deficiency states ,

✓extensive burns,

✓ brain edema

✓ ascites

•expensive

gelatines- made of collagen obtained

from tendons, skin and bones

- Small molecular weight - 35 kDa

(fast urinary excretion )

- short-term volume effect

- minimal effect on hemostasis

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 for supplementing intracellular volume, improving

reological properties of blood, and in anticoagulant therapy

- among colloids – the most often cause of anaphylactic

reactions

Hydroxyethyl starch (HAES/HES)-Synthesized 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- preferred:

✓show beneficial rheological effect and inhibition of blood platelets aggregation

✓ does not accumulate in plasma and tissues and does not affect hemostasis and renal function

Colloidal solutions

natural synthetic

Colloids in fluid therapy (6)

31

Colloids in fluid therapy (7)

Colloidal solutions - advantages :

allow for faster replenishment of intravascular fluid (hemorrhage,

shock)

compared to crystalloids provide faster, stronger and longer-lasting

volume effect

- remain for a long time in the intravascular compartment (2-12 hours)

- increase oncotic pressure, which leads to the movement of water into the vessel

have a positive impact on hemodynamics, organ perfusion and oxygensupply

- after administration of colloids an increase in intravascular volume is observed –

from 100 % to up to 400%

32

Colloids in fluid therapy (8)

Colloidal solutions -disadvantages :

can cause allergic reactions

after the administration of large amounts, they may cause:

price

- dilution effect of blood components: proteins, coagulation factors

- decrease in hematocrit level

33

should not accumulate in the plasma and tissues,

but readily undergo elimination from the body

Colloids in fluid therapy (9)

Ideal colloidal solution:

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

34

The End