INTERFACIAL PHENOMENA Flashcards
1
Q
a boundary between two states of matter
A
INTERFACE
2
Q
Pharmaceutical dispersions having 2 or more phases
A
heterogenous system
3
Q
gas-gas interface is ___
A
impossible
4
Q
Boundary of gas-solid or gas-liquid
A
SURFACE
5
Q
solid particles dispersed into a liquid
A
SUSPENSION
6
Q
drug-containing liquid is dispersed as droplets into an immiscible liquid
A
EMULSIONS
7
Q
every surface is an ____
A
INTERFACE
8
Q
significant factors that affect adsorption of drugs
A
Interfacial phenomena in pharmacy & medicine
9
Q
formed between two phases
A
INTERFACIAL PHASE
10
Q
affect drug delivery systems
A
INTERFACIAL PHENOMENA
11
Q
The force per unit length that must be applied parallel to the surface so as to counterbalance the inward pull
A
SURFACE TENSION
12
Q
Units of surface & interfacial tension
A
dynes/cm or N/m
13
Q
Force per unit length existing at the interface of two immiscible liquids
A
INTERFACIAL TENSION
14
Q
γ
A
suface tension
15
Q
γLL γLS γSS
A
interfacial tension
16
Q
- Most accurate method (liquid is undisturbed)
- For surface tension ONLY
A
CAPILLARY RISE METHOD
17
Q
formula for capillary rise method
A
γ = 1/2 rℎρg
18
Q
Principle:
* The force necessary to detach a Platinum-Iridium ring immersed at the surface or interface
A
Du Noűy Ring Method
19
Q
- Widely used for measuring surface and interfacial tensions
A
DuNoűy Tensiometer
20
Q
particle size between greater than 500 nm (0.5 μm)
A
coarse dispersions
21
Q
when the size of the dispersed particles is 1 to 500 nm
A
colloidal dispersion
22
Q
dispersion medium
A
External or continuous phase
23
Q
dispersed phase
A
internal phase
24
Q
Basic objective in the formulation
A
stable interfaces
25
The condition in which the particles **do not aggregate** and which they **remain uniformly distributed** throughout the dispersion.
PHYSICAL STABILITY
26
A **bounded space** or an **exact quantity** of a material
system
27
Consists of at least two phases with one or more **dispersed phase (internal)** contained in a single **continuous (external) phase**
DISPERSION
28
A distinct **homogenous part** of a system
phase
29
**oil** and **water** interface
liquid-liquid
30
interface between the **suspended** **solid particle** and the **suspending medium**
solid-liquid
31
Attraction between **like** molecules
COHESIVE FORCES
32
Attraction between **unlike** molecules
ADHESIVE FORCES
33
**what happens to the interfacial tension & surface tension** when the **cohesive attraction** between molecules of like phases is **greater** than the **adhesive attraction** of unlike molecules **found in the bulk phase**
INTERFACIAL & SURFACE TENSION INCREASES
34
**what happens to the interfacial tension & surface tension** when the **adhesive** attraction is **greater** than the **cohesive** attraction
interfacial & surface tensions decreases
35
# PHASE
Liquid surface, body of **water** **exposed** to atmosphere
GAS-LIQUID
36
# PHASE
Solid surface, **table top**
gas-solid
37
# PHASE
**emulsion**
liquid-liquid
38
# PHASE
**suspension**
liquid-solid
39
# PHASE
powder particles **in contact**
solid-solid
40
occurs due to **unbalanced cohesive forces** at the interface of a **liquid** and a **gas** or at the interface of **two liquids**
SURFACE TENSION
41
must be done **against** the **force of surface tension** to **move** a molecule from the **inner layers to the surface**
WORK
42
the molecules ____ of a liquid possess an **excess of potential energy** compared to the molecules in the bulk
near the surface
43
Molecules **near the surface** of liquids possess ____ as compared to molecules located at the bulk of the liquid
excess potential energy
44
Molecules **near the surface** of liquids **possess excess potential energy** as compared to molecules located at the bulk of the liquid
SURFACE FREE ENERGY
45
**energy** is ____ to the **size** of the **free
surface**
PROPORTIONAL
46
energy is proportional to the size of the free surface
SURFACE FREE ENERGY
47
**more molecules** will have this **excessive potential energy** if the **surface** of the liquid is ____
HIGHER
48
if the **surface** of the liquid **increases**, what will happen to the **energy** of the liquid
increases
49
Are **surface active agents** or **surfactants** (emulsifying agents)
AMPHIPHILES
50
**head** of amphiphiles
hydrophilic, polar
51
**tail** of amphiphiles
lipophilic, nonpolar
52
materials that **increase surface area** of dispersed phase with the dispersion medium by:
* **Lower** the **surface tension** or **interfacial** between two liquids or between a liquid and a solid
* **Lower surface free energy**
SURFACTANTS
53
causes **immiscible** phases to **resist** **mixing** and **shrink** their surfaces
interfacial or surface tension
54
Which is **higher**, surface tension or interface tension?
surface tension
## Footnote
**adhesive** attraction between **liquid and gas** interface or surface is **weaker** than the **adhesive** attraction between l**iquid and liquid** interface
55
what is **necessary** to **control** in the system when carrying out surface and interfacial tension **determination**
TEMPERATURE
55
56
At the **critical temperature**, surface tension becomes
zero
57
**surface tensions** of most liquids ____ within an **increase** in **temperature**
decrease
58
**work** that **must be done** to **increase surface area**
Surface free energy
59
What should be to **increase surface area**?
**Reduce** surface **free energy** and surface/interfacial **tension**
60
the addition of molecules that **moves** to the **interface**.
positive adsorption
61
the addition of molecules that **moves** to the **bulk** portion
negative adsorption
62
* a surfactant with a **negative charge**
* an example is **sodium lauryl sulfate**
* These surfactants are widely used in **cosmetics** and **pharmaceutical industries**; though they have an **unpleasant taste** and some have **skin irritation** properties.
**anionic** surfactants
63
* a surfactant with a **positive charge**
* an example is **dodecyl ammonium chloride**
* Most widely used are the **quaternary ammonium compounds**.
**Cationic** surfactants
64
* **not** electrolytes
* their surface-active portion has **no charge**
* an example is the **sorbitan fatty esters**.
**nonionic** surfactants
65
* are **zwitterions** that have **both** positive and negative charges
* an example is **alkyl betaines**.
**amphoteric** surfactants
66
In the **general** sense, **any material** that **affects** the **interfacial surface tension** can be considered a
surfactant
67
in the **practical** sense, ____ may act as wetting agents, emulsifiers, foaming agents, and dispersant
surfactants
68
Used to **classify surfactants**
HLB system
69
* Classifies the **non-polar** and **polar nature** of the **emulsifier**
* The **balance** of the **hydrophilic** and **lipophilic** properties of an **emulsifying** agent or emulsifier determines whether an **O/W** or **W/O emulsion will result**.
hydrophile-lipophile balance
70
the **presence** of a **greater concentration** of a material **at the surface** than is present at the bulk
ADSORPTION
71
* involves **strong bonds**
* typically **irreversible**
* can only form **monolayers**
chemisorption
72
* involves the **penetration** of the substance into the inner structure
* involves the **passage** of a drug **across a barrier membrane**
ABSORPTION
73
it is called ____ if a substance is **adsorbed** to the **surface** and **absorbed** into the **bulk**
SORPTION
74
Substances with part of their molecule lipophilic and part hydrophilic **move on their own** to the **surfaces** or **interfaces** of the liquid.
surface active ingredients
75
amphiphiles having **high** HLB values
HYDROPHILIC
76
water-loving
HYDROPHILIC
77
amphiphiles are having **low** HLB values
LIPOPHILIC
78
The **type of emulsion** is a **function of the relative solubility** of the surfactant, the **phase** in which it is **more soluble** being the **continuous phase**.
BANCROFT RULE
79
Emulsifier with a ____ HLB value is **soluble in water** and **results** in the formation of an **o/w** emulsion
HIGH
80
Emulsifier with a **high** HLB value is **soluble in water** and **results** in the formation of an ____ emulsion
O/W
81
emulsifier with **high** HLB value is soluble in
WATER
82
Emulsifier with ____ HLB value are **soluble in oil** and forms a **w/o** emulsions
LOW
83
Emulsifier **low** HLB value are **soluble in oil** and forms a ____ emulsions
w/o
84
Emulsifier with **Low** HLB value are **soluble** in
OIL
85
**high** HLB values
| HYDROPHILIC SURFACTANTS
9-12
86
**low** HLB values
| LIPOPHILIC SURFACTANTS
2-6
87
what do u call **low** HLB values (3-6) that forms **W/O** emulsifying agents
SPAN
88
what do u call **HIGH** HLB values (8-16) that forms **O/W** emulsifying agents
tween
89
HLB formula
HLB = 20 (1-S/A)
| s = saponification no (ester)
a = acid number (fatty acid ester)
90
Takes place from either **adjacent** liquid or gas phase
ADSORPTION AT SOLID INTERFACES
91
concerned with the following:
● Removal of **objectionable odor** from room and food
● Operation of a **gas mask**
● Measurement of **particle dimension** of powders
adsorption of **GASES** at the **SOLID**
92
concerned with the following:
● **Decolorizing** solution
● Absorption **chromatography**
● **Detergency** and **wetting**
Adsorption of **liquid** at **solid interfaces**
93
# The **Solid-Gas Interface** depends on:
the material used to **adsorb the gas**
ADSORBENT
94
# The **Solid-Gas Interface** depends on:
the substance **being adsorbed**
ADSORBATE
95
# TYPES OF ADSORPTION
➢ this adsorption is **reversible**, is the **removal** of the **adsorbate** from the **adsorbent** known as **desorption** (an **increase** of **temperature** and **reduced pressure**).
➢ The **adsorbate** can be **removed** from the **adsorbent** by **increasing** the **temperature**
(**Desorption**)
Physical adsorption or van der Waals adsorption
96
**Physical adsorption** is also known as
van der waals adsorption
97
removal of adsorbate from the adsorbent
DESORPTION
98
➢ **adsorbate is attached to the adsorbent** by primary chemical bonds, is **irreversible** unless the **bonds are broken**.
➢ **Activated charcoal** – a substance that can **absorb enormous amounts of gases or liquids**. It is the **residue** from the **destructive distillation** of various organic materials, treated to **increase its adsorptive powers**.
Chemical adsorption or chemisorption
99
# FACTORS AFFECTING ADSORPTION
The extent of **adsorption** of a solute is **inversely proportional** to its **solubility** in the solvent from which adsorption occurs.
SOLUBILITY OF THE ADSORBATE
100
# FACTORS AFFECTING ADSORPTION
Adsorption **increases** as the **ionization** of the drug is **suppressed**.
pH
101
# FACTORS AFFECTING ADSORPTION
The extent of adsorption is **proportional** to the **specific surface area**.
NATURE OF ADSORBENT
102
# FACTORS AFFECTING ADSORPTION
An **increase** in **temperature** **decreases** the **amount of adsorbed**
TEMPERATURE
103
# Principles that uses solid/liquid adsorption
A **complex process** involving the **removal of foreign matter** from surfaces.
DETERGENCY
104
are **surfactants** that are **used** for the **removal of dirt**.
DETERGENTS
105
a **surfactant** that when **dissolved in water**, **lowers** the **advancing contact angle** and aids in **displacing an air phase** at the surface and **replacing it with a liquid phase**.
WETTING AGENT
106
the **angle** between a **liquid droplet** and the **surface** over which it **spreads**.
CONTACT ANGLE
107
**Detergents** and **soaps** have the property called ____ which is a **complex process of removing dirt**.
DETERGENCY
108
a **stable structure** consisting of **air pockets enclosed within thin films of liquid**
FOAM
109
the **gas-in-liquid dispersion** being **stabilized** by a
FOAMING AGENT
110
**break foam**, examples are alcohol, ether, castor oil, and some surfactants.
ANTIFOAMING AGENTS
111
**potential at the solid surface** due to potential determining ion. It is the **difference in potential** between the **surface** and the **electroneutral region** of the solution
Electrothermodynamic (Nernst) potential, E
112
is the **difference in potential** between the surface of the **tightly bound layer** and the **electroneutral region** of the solution.
Electrokinetic or Zeta potential
113
**Low** zeta potential values lead to ____
FLOCCULATION
114
What is the **dynes per cm** existing at the interface between **oil** and **water**?
INTERFACIAL TENSION
115
# TRUE OR FALSE
Spans and tweens **increase** surface free energy
FALSE
116
# TRUE OR FALSE
**Hydrophilic** surfactants have **low** HLB values while **lipophilic** surfactants are having **high** HLB values
FALSE
117
# TRUE OR FALSE
The **greater** is the **adhesive attraction** between 2 **immiscible** liquids, the **lesser** is the **interfacial tension**
TRUE
118
# TRUE OR FALSE
**Amphiphiles** in **oil-in-water** emulsion will have **polar heads out** and in **water-in-oil** emulsion will have **polar heads in**
TRUE
119
# TRUE OR FALSE
Emulsifier with a **high** HLB value is **soluble** in **water** and **results** in the formation of an **o/w** emulsion
TRUE
120
The **addition** of these particles will **reduce** the **interfacial tension** and **produce** a **more stable** heterogeneous mixture
AMPHIPHILES /
SURFACTANTS /
SURFACE ACTIVE INGREDIENTS
121
