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FF2 > colloids > Flashcards

colloids Flashcards

1
Q

types of disperse systems based on size

A

molecular dispersions - less than 1nm
colloidal systems - 1nm-1um
coarse dispersions more than 1um

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2
Q

molecular dispersions

A
  • particles invisible in electron microscope

-pass through semipermeable membrane

-rapid diffusion

ex - ordinary molecules, oxygen molecules

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3
Q

colloidal systems

A

-particles detected under ultra microscope, electron microscope.

-pass through filter paper, but not through semi permeable membrane.

-diffuse very slowly

ex- natural and synthetic polymers

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4
Q

coarse dispersions

A

-visible under microscope
-dont pass through normal filter paper nor semi p. membrane

-particles dont diffuse

ex - normal emulsions and suspensions

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5
Q

a liquid in a liquid dispersion system can be

A

a coarse dispersion if its conventional meaning size is more than 1 nm

or a colloidal system if the dispersed phase particle size is in the range of 1nm-1um (micro/nano)

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6
Q

dispersed phase of solid in liquid in the colloidal range is known as

A

sol (present in liquid state)

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7
Q

What distinguishes sol from solutions

A

the particle size of the dispersed phase

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8
Q

sol gel transition
liquid to?

A

under specific pH/temp or addition of ions colloidal particles that are separated can join together to form a network forming a gel

conversion from sol to gel
liquid to semisolid

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9
Q

benefits of colloidal drug carriers

A

-modify the distribution of drug in body

-improve therapeutic index of drugs either thru increasing efficacy or reducing toxicity (reducing distribution to some parts)

-Extending the therapeutic potential (control the release of dosage forms)

-Reach sites of inflammation, infection and solid tumors by EPR effect. (enhanced permeation and retention)

-targeting specific cell types by attaching ligands

-protect drugs derived from biotechnology (PEPTIDES, PROTEINS, OLIGONUCLEOTIDES) from degradation in biological fluids and enhance their delivery into cells

-improve bioavailability by increasing diffusion through biological membrane

-protect against degradation and enzyme inactivation

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10
Q

types of colloids based on the interaction of the dispersed particles with dispersion medium

A

1- Lyophilic colloids- loves dispersion medium (solvent) - basically both are on good terms

ex if water is the continuous phase then is hydrophilic

2- Lyophobic- not on good terms

ex if water is continuous phase then its hydrophobic colloid

3- association colloids- amphiphilic

ex- surfactant micelles

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11
Q

a liquid in liquid colloid system is

A

an emulsion ex - microemulsion or nanoemulsion

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12
Q

result of solvent interaction/bonding

A

solvent sheath forms

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13
Q

type of molecules that are lyophilic

A

organic molecules

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14
Q

type of molecules that are lyophobic

A

inorganic molecules

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15
Q

types of molecules in association colloids

A

aggregates of small organic molecules or ions aka MICELLES

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16
Q

viscosity of dispersion medium on lyophilic

A

increases with increase of concentration of polymer (the dispersed phase)

therefore gel forms due to the networks of polymers increasing
-solvated and asymmetric

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17
Q

viscosity of dispersion medium on lyophobic

A

it is not changed
not solvated and symmetric

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18
Q

viscosity of dispersion medium on association colloids

A

increases with increase concentration of surfactants until cmc reached and micelles concentration also increases
unsymmetric

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19
Q

effect of lyophilic stability with added electrolytes

A

theyre stable , due to solvent sheath which avoids coalescence and formation of coarse dispersion.

lyophilic colloids exert a protective effect

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20
Q

effect of lyophobic stability with added electrolytes

A

unstable due to neutralization

21
Q

effect of association stability with added electrolytes

A

micelle concentration is reduced
salting out occurs

22
Q

preparation of colloids

A

lyophilic - happen spontaneously

lyophobic - need manipulation of procedures - not spontaneously

association - colloidal aggregates are formed spontaneously when the conc is above the CMC

23
Q

methods of prep for lyophobic

A

1) dispersion method - reducing coarse particle size to colloidal size

-peptization - addition of ions that will be adsorbed on surface thereby causing repulsion , separating aggregates so they form colloids

-Colloid mill
-Electric dispersion
-Ultrasonic irradiation

2) condensation method - chemical reactions

3) changing the solvent

Decreasing solubility by adding a solvent, this will cause precipitation and then we get the colloid

24
Q

purpose of purification of colloid methods

A

to get rid of impurities and obtain pure colloid by using a semipermeable membrane where only the solutes pass thru simple diffusion and the colloid remains

speed up the process of diffusion

25
Q

purification of colloids

A

1)Dialysis

2)Electrodialysis -application of electric potential across the semi membrane

3) Ultrafiltration - Application of a pressure or suction across a filter semimembrane

26
Q

Brownian movement is a

A

kinetic property of colloids

-bombardment of colloidal particles (dispersed phase) by the molecules of the dispersion medium - random movement

27
Q

why dont suspensions have brownian movement

A

because brownian movement decreases with increase in size

and suspensions are coarse dispersions therefore they are the largest in size

28
Q

Consequences of Brownian movement

A

1- Stability of colloids

2- Diffusion

3- Colligative properties

29
Q

types of colloid properties

A

1- Kinetic properties
2-Optical properties
3) Electric properties

30
Q

osmotic pressure

A

movement of solvent from diluted area to a concentrated area across a semipermeable membrane to make concentrations on both sides equal

31
Q

oncotic pressure

A

osmotic pressure exerted by colloids (proteins) in a solution

basically it’s induced by proteins ex albumin , in plasma or lymph fluid

pulling effect back into the capillaries

32
Q

when does oedema occur

A

it occurs when osmotic pressure decreases , therefore the ability of the fluids to move or enter from diluted to concentrated decreases, thus the fluids inside that are concentrated start to escape and accumulate causing fluid build up in surrounding tissues

33
Q

how can we differentiate between solutions and colloidal sols?

A

Through tyndall effect

where we,d pass a beam of light across them and if light scattering occurs meaning

if light is reflected back then it’s colloid sol since it would indicate that its size is big enough to do that

34
Q

why are particles in liquid charged?

A

1- Selective adsorption by colloid surface of a particular ionic species present in solution

2- Ionization of surface groups as COOH or NH2 and charge depends on pH

35
Q

in acidic medium what happens to amine on the surface of colloid

A

it becomes positive NH3+

36
Q

if protein in acid medium

A

the solution will be cationic

bc the amine group will ionized while acid is unionized

37
Q

Forces of interaction between colloidal particles

A

Electrostatic - charges on colloidal surface

  • particles having the same charge the electrons tic forces will result in repulsion therefore its stable

Van der Waals

strong when distance between particles is small

38
Q

zeta potential relationship with repulsion

A

the higher the zeta potential of magnitude regardless of the sign the stronger repulsion

39
Q

zeta potential

A

measure degree of electric charge on particles relative to bulk medium in which they are suspended

40
Q

what is the most important stability factor for lyophobic colloids

A

the electric charges on the particles

-zeta potential (REPULSION)

41
Q

consequences of small zeta potential

A

less repulsion
less stable
thin diffuse layer
small charge difference

42
Q

high concentration of electrolytes

A

1- compresses the double layer

2- Decreases the magnitude of the zeta potential therefore decrease in repulsion = unstable

43
Q

how do solvent sweat advantage to lyophilic

A

it prevents molecules to come close to eachother due to van deer waal forces

44
Q

why are colloidal dispersions more physically stable than suspensions

A

Bc they have lower sedimentation rate due to:

-smaller particle size

-brownian movement

45
Q

what is aggregation

A

collection of particles into groups

46
Q

types of aggregation

A

1- coagulation

-particles are closely aggregated and difficult to redisperse

-destructive and permanent

  • attractive forces very strong

2-flocculation

-particles are loosely aggregated in open structures

-reversible and temporary

-weak attractive forces

47
Q

coalescence

A

occurs in emulsions/micro emulsion and nanoemulsions

-particle structure is completely lost with formation of a single layer due to combing particles/droplets

IRREVERSIBLE , FAILURE / INSTABILITY

48
Q

WHAT phase do colloid systems form

A

they are non homogenous system

FF2 (4 decks)

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