T1 - Final Exam: New Material Flashcards
What is a homogenous dispersion?
A molecular dispersion
What is a heterogenous dispersion?
The dispersed phase (usually a particle of some type) is physically distinguishable from the dispersion medium
What is the components of a dispersion?
- Dispersed phase
- Dispersion media
What is dispersed phase?
The internal or continuous phase of a dispersion
What is the dispersion media?
External or continuous phases of a dispersion
How are dispersions classified?
- Phase
- Particle size
What are the dispersions of solid phases?
- Suppositories and medicaition sticks
- Gels
- Solid form
What are the dispersions of liquid phases?
- Crystal suspensions
- Emulsions
- Foams
What are the dispersions of gas phases?
- Smoke, aerosols, spray powder, inhalation dry powder
- Mist, unevaporated liquid sprays
What are the phase categories of dispersions?
- Solid
- Liquid
- Gas
What are the particle size categories of dispersions?
Colloidal dispersion (0.1 – 1000 nm)
Coarse dispersion (1 -200 micrometer)
What are the colloidal dispersion types?
- Lyophillic
- Lyophobic
- Association
What does it mean to be lyophilic?
- Solute has a strong affinity for medium
- Has polar regions from ionizable functional groups
How does having a polar region affect lyophilic colloids?
Enables hydration in aqueous environments
What are examples of lyophilic colloids?
- Proteins: albumin, gelatin
- Polysaccharides: natural gums, cellulose derivatives
What is a colloidal solution?
Macromolecular dispersions that are solvated by the medium
What is crystalloid solution?
Small molecule dispersion that are solvated by the medium
What states are hydrophilic colloids found in?
Solid or gel state
What is the difference between a sol and gel state?
In sol state, molecules move freely in solution
In gel state, molecules form connected networks resulting in increased viscosity
What is lyophobic?
Compounds lack polar groups to give them surface hydrophilicity
What are examples of lyophobic colloids?
Milk, lipid emulsions, nanocrystal suspensions
What is the problem of having hydrophobic colloids?
Tendency to aggregate
What is the predominate plasma protein?
Albumin
What is association colloid?
Formed by association of dissolved particles into a substance in the colloidal size range.
How does physiologic colloids maintain fluid balance in the body through hydrostatic pressure?
capillary hydrostatic pressure
What are examples of association colloids?
- Surfactant micelles
- Liposomes
What is a microemulsions?
Dispersion of oil-in-water or water-in-oil that is smaller than conventional emulsions
Thermodynamically favorable
What is CHP?
- Pressure exerted by blood against the wall of a capillary
- Drives the force that drives fluid out of capillaries to tissues
- As fluid exits a capillary and moves into tissues, the hydrostatic pressure in the interstitial fluid correspondingly rises
How does physiologic colloids maintain fluid balance in the body through colloidal oncotic pressure?
- Form of osmotic pressure induced by the proteins, notably albumin, in a blood vessel’s plasma (blood/liquid) that displaces water molecules
- Opposing effect of both hydrostatic blood pressure pushing water and small molecules out of the blood into the interstitial spaces within the arterial end of capillaries and interstitial colloidal osmotic pressure
What effect will administering hypertonic have on intracellular and extracellular volume?
Administering hypertonic solution will increase extracellular volume and decrease intracellular volume
What effect will administering hyportonic have on intracellular and extracellular volume?
Administering hypotonic solutions will increase both extracellular and intracellular volume
What effect will administering isotonic have on intracellular and extracellular volume?
Administering isotonic solutions will increase extracellular volume while not affecting intracellular volume
What effect will administering colloidal dispersions have on intravascular, interstitial and intracellular volume?
Administering colloidal dispersions will increase the intravascular volume and not intracellular or interstitial volume
What are the 3 association colloids?
- Surfactant micelle
- Microemulsions
- Liposome
What are surfactant micelles?
Form spontaneously when CMC is reached 2-5 nm
What is a liposome?
More complex bilayer structures 50-100 nm may become large enough to exceed colloidal size range
What is Brownian motion?
Random, irregular movement of particles
What causes Brownian motion?
Bombardment of particles by the molecules of the dispersion media
What is particle movement affected by?
- Particle size
- Viscosity of medium
- Temperature
What are the major factors affecting distribution uniformity
- Brownian motion
- Gravitational forces
- Dispersion particle growth
What does bombardment by medium molecules?
- The higher the energy, the more particle movement is observed.
- Brownian motion stops at Absolute Zero
What decreases the effect of Brownian motion?
- Decrease temp
- Increase viscosity
- Increase particle size
What are colloidal particles?
- Particles are small enough that Brownian Motion keeps particles suspended
- Unique to colloidal dispersion
- Can counteract gravitational forces
How are colloidal aggregates affected by gravitational forces?
Behave in a predictable manner
How would particles sediment according to Stokes Law?
- Course dispersion like suspensions will sediment down
- Oil and water emulsion will sediment up (creaming)
Describe the rate of sedimentation?
- Inversely related to viscosity
- Proportional to density and particle diameter
What is aggregation?
- Particles tend to aggregate together
- Both reversibly and irreversibly
What occurs in a coarse dispersion like suspension or emulsion?
- Molecules at the interface between the particle and the dispersion media are subject to different forces than those molecules within the particle.
- The interfacial molecules will have lower binding energy with interior molecules
- The result of this is a positive surface energy.
- Magnitude of the surface energy depends on the collective cohesive and adhesive forces within a particular system
What occurs when particle size is reduced?
- Surface area is increased
- More molecules are in contact with dispersion media
- Free surface energy rises
- Result is aggregation and dispersion stability is impaired
What causes aggregation to occur or not occur?
Forces surrounding particle interactions
What is the DVLO theory?
2 primary forces that determine whether aggregation in a suspension
What are the 2 potentials of DVLO theory?
- Van der Waals attraction
- Electrostatic repulsion
Describe how Van der Waals and Electrostatic potential can affect aggregation
- Both potentials occur simultaneously to differing degrees within a system
- Each potential approaches zero as distance between particles increases
- Which positive or negative predominate will determine whether aggregation occurs
What are the Non-DVLO forces?
- Hydration
- Steric
What occurs during a hydration force?
- Occurs with hydrophilic colloids
- Water molecules may interact and get much closer than electrostatic forces while competing with van der Waals forces.
- The net result is repulsion which keeps the colloidal particles apart
What occurs during a steric forces?
- Coating of particles with polymeric materials
- Creates a physical barrier which prevents van der Waals attractive forces
What is Ostwald ripening?
Creation of large particles at the expense of smaller ones
According to Ostwald ripening, what happens when particles are added to a solution?
- Smaller particles will undergo dissolution faster the larger particles
- As this occurs, the solutes from smaller particles diffuse toward and deposit on larger particles.
- Growth in particle size results
- As dissolution progresses, the smaller particles continue to get smaller perpetuating the large particle growth.
- Any effect that increases dissolution will increase this ripening.
What is van de waal forces?
- Attractive forces between molecules created from fluctuations in electron density.
- Creates dipole-induced dipole interactions
- These are weak between individual molecules
- With particles, however, the collective forces can create a strong attraction
What is electrostatic forces?
- Depend on the magnitude of surface charge
- Magnitude of surface charge comes from:
Ionizable groups on particle molecules
Adsorption of ions from solution onto uncharged particle surface
What is a shear plane?
Boundary between the diffuse layer and the dispersion medium surrounding the particle
What is difference between the stem and diffuse layer?
- Stem: when particles within the medium, counterions bound
- Dif: Fraction of the ions stay with the particle
What happens to weak bound ions the diffuse layer?
Pulled away with particle movement
What is zeta potential?
The net electric charge at the outer diffuse layer the occurs at the shear plane
What happens if there is an increase in zeta potential?
The more repulsion (electrostatic potential) between particles is present
Describe the magnitudes of particle interactions
Van der Waal is attractive potential that is represented negatively
Electrostatic repulsive potential have positive value
What do the curve of particle interactions represent?
The strength of the attraction as particles come closer together
How is net interaction potential curve produced?
Subtracting the repulsive and attractive potentials as a given distance
What is the difference between net interaction energy and primary minimum?
Net: Positive repulsive energy barrier (electrical repulsion dominates) must be overcome
Prim: As particles get closer, the negative and strong van der Waals attractive potential can create an energy trap
How can salts alter potential energy?
- Add counter ions to the diffuse layer
- Reduce repulsion
- Charge neutralization is closer to the particle
- Van der Waals can become more dominant at distance creating a weak secondary minimum
- Particles weakly coming together to form floccules which are easily resuspended
What are the properties of the flocculated suspensions?
- A suspension in which particles have undergone flocculation
- Has floccules
- The rate of sedimentation is high
- The volume of sediment is high
- Form porous sediments
- The redispersion of sediment can easily by done by agitation
What plays a significant role on adsorption?
Electrical charges on both the solid adsorbent and liquid absorbate
What is responsible for physical adsorption from solution onto the solids?
Hydrogen bonds and van der waals forces that are weak attractive forces
What is responsible to chemisorption?
Ion exchange and other strong attractive forces
What is the relationship between solubility and adsorption?
- Inversely related
- The lower solubility the higher the adsorption
What is the relationship between adsorption and pH?
- Affects the degree of ionization of the drug and its solubility
- Unionized forms will be more adsorbent than ionized species
What is relationship between adsorption and temperature?
Adsorption is an exothermic process, therefore decreasing temp will enhance the adsorption process
What are floccules?
Form loose agglomerations of particles
What is rheology?
The study of flow, addresses the viscosity characteristics of powders, fluids, and semisolids
How does surface area affect adsorbent?
The smaller the particle size or the more porous the solid, the higher the capacity of adsorption
What adsorbents absorb more effectively to non polar compounds?
Non polar
What is an amphiphile?
Have both hydrophobic and lipophilic portions of their molecules
What are examples of zwitterionic surfactants?
Phospholipids
What is the use of zwitterionic surfactants?
Co-surfactant to boost foaming properties
How does pH affect zwitterionic surfactants?
Depending on pH their, they can be anionic, cationic, or zwitterionic