CEE 2. PhyPharm Quiz 2

pH

a measure of the acidity and alkalinity of a solution 

neutral

pH is numerically equal to 7 for ___ solutions

Ionization

complete separation of ions in a crystal lattice when salt is dissolved

Dissociation

separation of ions in solution when the ions are associated by interionic interaction

increasing

pH is ___ with increasing alkalinity

decreasing

pH is ___ with increasing acidity

Buffers

Solutions that have the property of resisting changes in pH when acids or bases are added to them

Buffers results from the presence of a buffer pair which consists of either:

1. Weak acid and some salt of a weak acid and/or its conjugate base
2. Weak base and some salt of a weak base and/or its conjugate acid

Buffer capacity

Refers to the ability of a buffer solution to resist changes in pH upon addition of acid/alkali

pH = pKa

Maximum buffer capacity occurs when ___

Interfacial phenomenon

Attributed to the effects of molecules found at the interface (boundary between two phases)

Tension

force which resists in contact area between two phases resulting in immiscibility of phases.

Surfactants

Substances acting on the interface which lower the surface-free energy or lower surface tension

Griffin-HLB system

1. ↑HLB – hydrophilic
2. ↓HLB – hydrophobic or lipophobic

1–3

Anti-foaming (HLB VALUE)

3-8

Water-in-oil (HLB VALUE)

7-9

Wetting Agent (HLB VALUE)

* 8 – 16
* 9 – 12

Oil-in-water (HLB VALUE)

13-16

Detergent (HLB VALUE)

16 – 19

\
Solubilizer (HLB VALUE)

Cohesion

Attraction among SIMILAR molecules

Adhesion

Attraction among DIFFERENT molecules

Capillarity

Tendency of a liquid to rise up a normal tube

Capillarity

result of surface or interfacial forces

True

The rise of water in a thin tube inserted in water is caused by forces of attraction between the molecules of water and the glass walls and among the water molecules.

True

↑adhesive force - ↑capillarity

False

↑adhesive force - ↓capillarity

Colloidal dispersions

A system in which solid particles of colloidal size (1 nm – 0.5 μm) are dispersed in a continuous phase of a different composition.

1. lyophilic
2. lyophobic
3. association colloids

Colloidal dispersion classes (3)

Lyophilic colloids

spontaneous; thermodynamically stable

Lyophobic colloids

non-spontaneous; thermodynamically unstable

aka “amphiphilic colloids”

Association colloids

Association colloids

having both hydrophilic and lipophilic regions in the same molecule; preparation involves surfactants which can accumulate and form a micelle.

1. Optical: Faraday-Tyndall effect
2. Kinetic: Brownian movement
3. Electric: Nernst potential (Electrothermodynamic potential)

PROPERTIES OF COLLOIDS (3)

Optical

Faraday-Tyndall effect

Kinetic

Brownian movement

Electric

Nernst potential (Electrothermodynamic potential)

Optical: Faraday-Tyndall effect

ability to scatter or disperse light

Kinetic: Brownian movement

colloidal particles appear as tiny points of light in constant motion when examined under an ultramicroscope

Diffusion

spontaneous movement of particles from a region of higher concentration to one of lower concentration until equilibrium is achieved

Electric: Nernst potential (Electrothermodynamic potential)

difference between the actual surface of the particle and the electroneutral region of the dispersion; 

Zeta potential (Electrokinetic potential)

difference in potential between the surface of the tightly-bound layers and the electroneutral region of the dispersion, has more application in pharmacy

0\.5 μm

Coarse dispersion particle size 

Phase inversion

o/w to w/o or vice-versa

Cracking

total separation of the 2 phases

Creaming

upward or downward movement of the internal phase of the emulsion

Sedimentation

downward movement

Aggregation

globules come together but do not fuse

Coalescence

globules come together and fuse

Rheology

Study of flow

Rheology

Scientific study of the deformation and flow properties of matter

Greek *rheos*

“to flow”

*logos*

“study”

Viscosity

resistance to flow

Viscosity

reciprocal of fluidity

shear stress (F) to the shear rate (G)

Viscosity ratio

1. Absolute viscosity
2. Kinematic viscosity
3. Relative viscosity

Classes of viscosity (3)

\

1. Newtonian flow
2. Non-newtonian flow

Flow systems (2)

Plastic / Bingham Bodies

Simplest type of non-Newtonian behavior in which the curve is linear only at values of F, beyond the yield value.

Yield value

force that should be exceeded for a Bingham body (plastic) to flow

Pseudoplastic

shear THINNING

Increase (↑) G (shear rate): ↓ viscosity (η)

Pseudoplastic (ratio)

Dilatant

shear THICKENING

Increase (↑) G (shear rate): ↑ viscosity (η)

\
Dilatant (ratio)

True

\
When stress is removed a dilatant system returns to its original state of fluidity.

Thixothropy

Breakdown of structure (shear-thinning) that does not reform immediately when stress is removed or reduced.

Thixothropy

Is an isothermal and slow recovery (on standing of a material) of a consistency lost through shearing.

Thixothropy (ratio)

Increase (↑) time; ↓ viscosity (η)

Hysteresis loop

the curve obtained on increasing shear stress is NOT superimposable with that obtained on decreasing shear stress.

Rheopexy

A phenomenon in which a solid forms a gel more readily when gently shaken or otherwise sheared than when allowed to form the gel while the material is kept at rest.

Rheopexy (ratio)

Increase (↑) time; ↑ viscosity (η)

SOLID STATE

* Characterized of having FIXED shapes
* Nearly incompressible
* Having strong intermolecular forces
* Very little kinetic energy
* Their atoms vibrate in fixed positions about an equilibrium position, and so there is very little translational motion.

Crystalline

The molecules or atoms are arranged in repetitious three-dimensional lattice units.

polymorphism

phenomenon wherein a solid may exist in more than one crystalline form

Amorphous

* Glasses
* Non-crystalline, no definite order or arrangement
* Molecules arranged in random manners
* Isotropic

Amorphous is also referred to as

supercooled liquids

Micromeritics

Study of small particles

Fundamental

Inherent in all particles

Derived individual shape

Combination of fundamental properties

OPTICAL MICROSCOPY

Use of microscope to measure individual particle

individual particles can be seen

\
OPTICAL MICROSCOPY advantage

very tedious, 2D-image only

OPTICAL MICROSCOPY disadvantage

**Feret diameter**

2 tangents separated by the longest distants

**Martin diameter**

distance that will bisect the particle into halves

**Projected area of the circle**

diameter of the circle that will enclose the particle

SIEVE ANALYSIS

* USP Method
* Sieve number (Mesh number)
* Number of opening per linear inch

Attrition of particles

SIEVE ANALYSIS disadvantage

SEDIMENTATION METHOD

Sedimentation rate or free fall velocity of particles

Andreasen apparatus or pipet

SEDIMENTATION METHOD Apparatus

Stoke’s Law

SEDIMENTATION METHOD Principle

1. Coulter counter
2. HIAC/Royco instrument
3. Gelman Counter

AUTOMATIC PARTICLE COUNTER (3)

Coulter counter

Measures the change in ER

Coulter counter principle

Electric resistance

Coulter counter (increase/decrease)

↑ Electric resistance; ↑ particle size

HIAC/Royco instrument principle

Light blockade

HIAC/Royco instrument (increase/decrease)

↓ light passed; ↑ particle size

Gelman Counter principle

Faraday-Tyndall effect

PARTICLE VOLUME

space occupied by the powder

POROSITY (ε)

measurement of the total voids/spaces of particle/s

Methods of determining the flow properties of powders:

1. Angle of repose
2. Carr’s compressibility index
3. Hausner’s Ratio