The document discusses interfaces and surface/interfacial phenomena. It defines an interface as the boundary between two phases and notes that interfacial molecules have different properties than bulk molecules. It discusses different types of interfaces that can exist depending on whether the adjacent phases are solid, liquid, or gas. It then discusses several important interfacial phenomena in pharmacy, including drug adsorption, membrane penetration, emulsion formation/stability, and particle dispersion in liquids to form suspensions.
In this presentation:
Surface Tension
Interfacial Tension
Definition of inerfacial tension in different ways
Measurement of interfacial and surface tesion
State of matter and properties of matter (Part-6)(Relative humidity, Liquid ...Ms. Pooja Bhandare
RELATIVE HUMIDITY, Humidity, Wet and Dry Hygrometer, LIQUID COMPLEX, LIQUID CRYSTALS, Types of liquid crystals, GLASSY STATES, Characteristics glassy state, Types of glassy state, What is the Glass Transition Temperature?
State of matter and properties of matter (Part-2) (Latent Heat, Vapour pressu...Ms. Pooja Bhandare
Latent Heat, Vapour pressure, Factor affecting vapour pressure, Surface area, Types of molecule, Temperature and Intermolecular forces, Sublimation Critical point
In this presentation:
Surface Tension
Interfacial Tension
Definition of inerfacial tension in different ways
Measurement of interfacial and surface tesion
State of matter and properties of matter (Part-6)(Relative humidity, Liquid ...Ms. Pooja Bhandare
RELATIVE HUMIDITY, Humidity, Wet and Dry Hygrometer, LIQUID COMPLEX, LIQUID CRYSTALS, Types of liquid crystals, GLASSY STATES, Characteristics glassy state, Types of glassy state, What is the Glass Transition Temperature?
State of matter and properties of matter (Part-2) (Latent Heat, Vapour pressu...Ms. Pooja Bhandare
Latent Heat, Vapour pressure, Factor affecting vapour pressure, Surface area, Types of molecule, Temperature and Intermolecular forces, Sublimation Critical point
INCLUDES SPREADING COEFFICIENT AND ITS THEORY AND ALSO FEW OF ITS APPLICATION IN PHARMACEUTICAL FIELD
WILL BE HELPFUL FOR B PHARMACY STUDENTS
INCLUDES HOW IT IS DERIVED AND ALSO HOW IT IS RELATED TO SPREADING OF A CREAM OR OINTMENT ON OUR SKIN
IMPORTANCE OF SPREADING COEFFICIENT
Quantitative approach to the to the factor influcing solubility of drug; (Sol...Ms. Pooja Bhandare
Quantitative approach to the to the factor influcing solubility of drugs, Temperature,Nature of solvent, The boiling point of the liquids and the melting point of solids,Crystal properties:
Particle size (surface area ) of drug particles: The influence of substituent’s in molecular structures, Molecular size:
. pH :
Surface Tension is defined as the tension of the surface film of a liquid caused by the attraction of the particles in the surface layer by the bulk of the liquid, which tends to minimize surface area.
It is due to the phenomena of surface tension that the drops of water tend to assume a spherical shape to attain minimum surface area. the presentation gives a brief description of the methods to measue this important property of the interface of two fluid.
Solubility of liquids in liquids, The term miscibility refers to the mutual solubility of the component of liquid - liquid system, Raoult’s Law, Raoult’s law may be mathematically expressed as: Ideal solution, Real solution
Surface and Interfacial tension [Part-3(a)](Measurement of Surface and Inter...Ms. Pooja Bhandare
MEASUREMENT OF SURFACE AND INTERFACIAL TENSION
Capillary Rise Method, Drop Count and Weight Method.
Wilhelmy Plate Methods ,The DuNouy Ring Method.
Capillary Rise Method: Upward force due to surface tension: Drop count and Weight method Downward Force: Drop weight method: Drop count method
INCLUDES SPREADING COEFFICIENT AND ITS THEORY AND ALSO FEW OF ITS APPLICATION IN PHARMACEUTICAL FIELD
WILL BE HELPFUL FOR B PHARMACY STUDENTS
INCLUDES HOW IT IS DERIVED AND ALSO HOW IT IS RELATED TO SPREADING OF A CREAM OR OINTMENT ON OUR SKIN
IMPORTANCE OF SPREADING COEFFICIENT
Quantitative approach to the to the factor influcing solubility of drug; (Sol...Ms. Pooja Bhandare
Quantitative approach to the to the factor influcing solubility of drugs, Temperature,Nature of solvent, The boiling point of the liquids and the melting point of solids,Crystal properties:
Particle size (surface area ) of drug particles: The influence of substituent’s in molecular structures, Molecular size:
. pH :
Surface Tension is defined as the tension of the surface film of a liquid caused by the attraction of the particles in the surface layer by the bulk of the liquid, which tends to minimize surface area.
It is due to the phenomena of surface tension that the drops of water tend to assume a spherical shape to attain minimum surface area. the presentation gives a brief description of the methods to measue this important property of the interface of two fluid.
Solubility of liquids in liquids, The term miscibility refers to the mutual solubility of the component of liquid - liquid system, Raoult’s Law, Raoult’s law may be mathematically expressed as: Ideal solution, Real solution
Surface and Interfacial tension [Part-3(a)](Measurement of Surface and Inter...Ms. Pooja Bhandare
MEASUREMENT OF SURFACE AND INTERFACIAL TENSION
Capillary Rise Method, Drop Count and Weight Method.
Wilhelmy Plate Methods ,The DuNouy Ring Method.
Capillary Rise Method: Upward force due to surface tension: Drop count and Weight method Downward Force: Drop weight method: Drop count method
SURFACE TENSION, INTERFACIAL TENSION, SURFACE FREE ENERGY, Measurement of surface and interfacial tension-capillary rise method, drop number method, drop weight method, Du Nuoy tensiometer method, Spreading of liquids, spreading coefficient, surface active agents, hydrophilic-lipophilic balance, soluble monolayers, Adsorption on solid surface, Isotherms
When phases exist together, the boundary between two of them is known as interface.
When the phase is in contact with atmosphere it is termed as surface.
Cancer cell metabolism: special Reference to Lactate PathwayAADYARAJPANDEY1
Normal Cell Metabolism:
Cellular respiration describes the series of steps that cells use to break down sugar and other chemicals to get the energy we need to function.
Energy is stored in the bonds of glucose and when glucose is broken down, much of that energy is released.
Cell utilize energy in the form of ATP.
The first step of respiration is called glycolysis. In a series of steps, glycolysis breaks glucose into two smaller molecules - a chemical called pyruvate. A small amount of ATP is formed during this process.
Most healthy cells continue the breakdown in a second process, called the Kreb's cycle. The Kreb's cycle allows cells to “burn” the pyruvates made in glycolysis to get more ATP.
The last step in the breakdown of glucose is called oxidative phosphorylation (Ox-Phos).
It takes place in specialized cell structures called mitochondria. This process produces a large amount of ATP. Importantly, cells need oxygen to complete oxidative phosphorylation.
If a cell completes only glycolysis, only 2 molecules of ATP are made per glucose. However, if the cell completes the entire respiration process (glycolysis - Kreb's - oxidative phosphorylation), about 36 molecules of ATP are created, giving it much more energy to use.
IN CANCER CELL:
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
introduction to WARBERG PHENOMENA:
WARBURG EFFECT Usually, cancer cells are highly glycolytic (glucose addiction) and take up more glucose than do normal cells from outside.
Otto Heinrich Warburg (; 8 October 1883 – 1 August 1970) In 1931 was awarded the Nobel Prize in Physiology for his "discovery of the nature and mode of action of the respiratory enzyme.
WARNBURG EFFECT : cancer cells under aerobic (well-oxygenated) conditions to metabolize glucose to lactate (aerobic glycolysis) is known as the Warburg effect. Warburg made the observation that tumor slices consume glucose and secrete lactate at a higher rate than normal tissues.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Richard's aventures in two entangled wonderlandsRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
Seminar of U.V. Spectroscopy by SAMIR PANDASAMIR PANDA
Spectroscopy is a branch of science dealing the study of interaction of electromagnetic radiation with matter.
Ultraviolet-visible spectroscopy refers to absorption spectroscopy or reflect spectroscopy in the UV-VIS spectral region.
Ultraviolet-visible spectroscopy is an analytical method that can measure the amount of light received by the analyte.
Slide 1: Title Slide
Extrachromosomal Inheritance
Slide 2: Introduction to Extrachromosomal Inheritance
Definition: Extrachromosomal inheritance refers to the transmission of genetic material that is not found within the nucleus.
Key Components: Involves genes located in mitochondria, chloroplasts, and plasmids.
Slide 3: Mitochondrial Inheritance
Mitochondria: Organelles responsible for energy production.
Mitochondrial DNA (mtDNA): Circular DNA molecule found in mitochondria.
Inheritance Pattern: Maternally inherited, meaning it is passed from mothers to all their offspring.
Diseases: Examples include Leber’s hereditary optic neuropathy (LHON) and mitochondrial myopathy.
Slide 4: Chloroplast Inheritance
Chloroplasts: Organelles responsible for photosynthesis in plants.
Chloroplast DNA (cpDNA): Circular DNA molecule found in chloroplasts.
Inheritance Pattern: Often maternally inherited in most plants, but can vary in some species.
Examples: Variegation in plants, where leaf color patterns are determined by chloroplast DNA.
Slide 5: Plasmid Inheritance
Plasmids: Small, circular DNA molecules found in bacteria and some eukaryotes.
Features: Can carry antibiotic resistance genes and can be transferred between cells through processes like conjugation.
Significance: Important in biotechnology for gene cloning and genetic engineering.
Slide 6: Mechanisms of Extrachromosomal Inheritance
Non-Mendelian Patterns: Do not follow Mendel’s laws of inheritance.
Cytoplasmic Segregation: During cell division, organelles like mitochondria and chloroplasts are randomly distributed to daughter cells.
Heteroplasmy: Presence of more than one type of organellar genome within a cell, leading to variation in expression.
Slide 7: Examples of Extrachromosomal Inheritance
Four O’clock Plant (Mirabilis jalapa): Shows variegated leaves due to different cpDNA in leaf cells.
Petite Mutants in Yeast: Result from mutations in mitochondrial DNA affecting respiration.
Slide 8: Importance of Extrachromosomal Inheritance
Evolution: Provides insight into the evolution of eukaryotic cells.
Medicine: Understanding mitochondrial inheritance helps in diagnosing and treating mitochondrial diseases.
Agriculture: Chloroplast inheritance can be used in plant breeding and genetic modification.
Slide 9: Recent Research and Advances
Gene Editing: Techniques like CRISPR-Cas9 are being used to edit mitochondrial and chloroplast DNA.
Therapies: Development of mitochondrial replacement therapy (MRT) for preventing mitochondrial diseases.
Slide 10: Conclusion
Summary: Extrachromosomal inheritance involves the transmission of genetic material outside the nucleus and plays a crucial role in genetics, medicine, and biotechnology.
Future Directions: Continued research and technological advancements hold promise for new treatments and applications.
Slide 11: Questions and Discussion
Invite Audience: Open the floor for any questions or further discussion on the topic.
2. Interface is the boundary between two or more phases
exist together
The properties of the molecules forming the interface are
different from those in the bulk that these molecules are
forming an interfacial phase.
Several types of interface can exist depending on whether
the two adjacent phases are in solid, liquid or gaseous state.
Important of Interfacial phenomena in pharmacy:
Adsorption of drugs onto solid adjuncts in dosage forms
Penetration of molecules through biological membranes
Emulsion formation and stability
The dispersion of insoluble particles in liquid media to form
suspensions.
3. LIQUID INTERFACES
Surface and Interfacial Tensions
In the liquid state, the cohesive forces between
adjacent molecules are well developed.
For the molecules in the bulk of a liquid
They are surrounded in all directions by other molecules for
which they have an equal attraction.
For the molecules at the surface (at the liquid/air interface)
Only attractive cohesive forces with other liquid molecules
which are situated below and adjacent to them.
They can develop adhesive forces of attraction with the
molecules of the other phase in the interface
The net effect is that the molecules at the surface of the
liquid experience an inward force towards the bulk of the
liquid and pull the molecules and contract the surface with
a force F .
4. To keep the equilibrium, an equal force must be applied to
oppose the inward tension in the surface.
Thus SURFACE TENSION [γ ] is the force per unit length that must
be applied parallel to the surface so as to counterbalance the net
inward pull and has the units of dyne/cm
INTERFACIAL TENSION is the force per unit length existing at the
interface between two immiscible liquid phases and has the units
of dyne/cm.
Invariably, interfacial tensions are less than surface tensions
because an adhesive forces, between the two liquid phases
forming the interface are greater than when a liquid and a gas
phase exist together.
If two liquids are completely miscible, no interfacial tension exists
between them.
Greater surface tension reflects higher intermolecular force of
attraction, thus, increase in hydrogen bonds or molecular weight
cause increase in ST
5. The work W required to create a unit area of surface is
known as SURFACE FREE ENERGY/UNIT AREA (ergs/cm2)
erg = dyne . cm
Its equivalent to the surface tension γ
Thus the greater the area A of interfacial
contact between the phases, the greater the free energy.
W = γ ∆ A
For equilibrium, the surface free energy
of a system must be at a minimum.
Thus Liquid droplets tend to assume a
spherical shape since a sphere has the
smallest surface area per unit volume.
6. Methods for measuring surface and interfacial tension
1- Capillary rise method
2- Ring (Du Nouy) tensiometer
3- Drop weight method (Stalagmometer)
The choice of the method for measuring surface
and interfacial tension depend on:
Whether surface or interfacial tension is to be determined.
The accuracy desired
The size of sample.
7. Capillary Rise Method
When a capillary tube is placed in a liquid, it
rises up the tube a certain distance. By measuring
this rise, it is possible to determine the surface
tension of the liquid. It is not possible, to obtain
interfacial tensions using the capillary rise
method.
Cohesive force is the force existing between like
mole-cules in the surface of a liquid
Adhesive force is the force existing between
unlike molecules, such as that between a liquid
and the wall of a glass capillary tube
When the force of Adhesion is greater than the
cohesion, the liquid is said to wet the capillary
wall, spreading over it, and rising in the tube.
The Principle
8. If a capillary tube of inside radius =r immersed in a liquid
that wet its surface, the liquid continues to rise in the tube
due to the surface tension, until the upward movement is
just balanced by the downward force of gravity due to the
weight of the liquid
a = γ cos Ө
a = 2 π r γ cos Ө
The upward component of the force resulting from
the surface tension of the liquid at any point on the
circumference is given by:
Thus the total upward force around the inside
circumference of the tube is
Where
Ө = the contact angle between the surface of the
liquid and the capillary wall
2 π r = the inside circumference of the capillary.
For water the angle Ө is insignificant, i.e. the liquid
wets the capillary wall so that cos Ө = unity
Cont. angle
water and glass
Cont. angle
Mercury and glass
9. The downward force of gravity
(mass x acceleration) is given by
Where:
π r 2 = the cross-sectional area
h = the height of the liquid column to
the lowest point of the meniscus
(p – p o) = the difference in the density of the
liquid p and its vapor po
g = the acceleration of gravity
w = the weight of the upper part of the meniscus.
At Maximum height, the opposing forces are in equilibrium
p o, Ө and w can usually be disregarded
Hence the surface tension can be calculated.
π r 2 h (p – p o) g + w
2 π r γ cos Ө = π r 2 h (p – p o) g + w
2 π r γ = π r 2 h p g γ = 1/2 r h p g
10. Ring (Du Nouy) Tensiometer
the principle of the instrument depends on the fact that:
the force necessary to detach a platinum-iridium ring
immersed at the surface or interface is proportional to the
surface or interfacial tension.
The force of detachment is recorded in dynes
on a calibrated dial
The surface tension is given by:
Where:
F = the detachment force
R1 and R 2= the inner and outer radii of the ring.
γ = F / 2 π (R1 + R2)
For measuring surface and interfacial tensions.
The principle
11. If the volume or weight of a drop as it is detached
from a tip of known radius is determined, the surface
and interfacial tension can be calculated from
Where m = the mass of the drop
V = the volume of the drop
p = the density of the liquid
r = the radius of the tip
g = the acceleration due to gravity
Φ = a correction factor
The correction factor is required as not all
the drop leaves the tip on detachment
The tip must be wetted by the liquid so as
the drop doesn’t climb the outside of the tube.
Φ V pg=Φ mgγ =
2 π r 2 π r
Drop Weight and drop volume method
12. A surfactant molecule is depicted schematically as a cylinder
representing the hydrocarbon (hydrophobic) portion with a
sphere representing the polar (hydrophilic) group attached
at one end.
The hydrocarbon chains are straight because rotation around
carbon-carbon bonds bends, coils and twists them.
Sodium Lauryl
Sulfate molecule
13. Molecules and ions that are adsorbed at interfaces are
termed surface active agents, surfactants or amphiphile
The molecule or ion has a certain affinity for both polar and
nonpolar solvents.
Depending on the number and nature of the polar and
nonpolar groups present, the amphiphile may be hydrophilic,
lipophilic or be reasonably well-balanced between these two
extremes.
It is the amphiphilic nature of surface active agents which
causes them to be adsorbed at interfaces, whether these be
liquid/gas or liquid/liquid.
14. A scale showing classification of
surfactant function on the basis of
HLB values of surfactants.
The higher the HLB of a surfactant
the more hydrophilic it is.
Example: Spans with low HLB are
lipophilic. Tweens with high HLB are
hydrophilic.
15. Determination of HLB
Polyhydric Alcohol Fatty Acid Esters (Ex. Glyceryl monostearate)
HLB = 20 ( 1 – S / A )
Surfactants with no Saponification no (Ex. Bees wax and lanolin)
S = Saponification number of the ester
A = Acid number of the fatty acid
HLB =E + P / 5
E = The percent by weight of ethylene oxide
P=The percent by weight of polyhydric alcohol group in the molecules
Surfactants with hydrophilic portion have only oxyethylene groups
HLB =E / 5
16. When a liquid is placed on the surface of other liquid, it will
spread as a film if the adhesion force is greater than the
cohesive forces.
17. As surface or interfacial work is equal to surface
tension multiplied by the area increment.
The work of cohesion, which is the energy required to
separate the molecules of the spreading liquid so as it can
flow over the sub-layer=
Where 2 surfaces each with a surface tension = γ L
The work of adhesion, which is the energy required to break
the attraction between the unlike molecules=
Where: γ L =the surface tension of the spreading liquid
γ S =the surface tension of the sub-layer liquid
γ LS =the interfacial tension between the two liquids.
Spreading occurs if the work of adhesion is greater than the
work of cohesion, i.e. Wa > Wc or Wa - Wc > 0
Wc = 2 γ L
Wa = γ L + γ S - γ LS
18. Spreading Coefficient is The difference between
the work of adhesion and the work of cohesion
S = Wa - Wc = (γ L + γ S - γ LS ) - 2 γ L
S = γ S - γ L - γ LS
S = γ S – (γ L + γ LS )
Spreading occurs (S is positive) when the surface tension
of the sub-layer liquid is greater than the sum of the surface
tension of the spreading liquid and the interfacial tension
between the sub-layer and the spreading liquid.
If (γ L + γ LS ) is larger than YS , (S is negative) the substance
forms globules or a floating lens and fails to spread over the
surface.
Liquid Substrate
19. Factor affecting Spreading Coefficient
Molecular Structural:
o The greater the polarity of the molecule the more positive [S]
as ethyl alcohol and propionic acid
o Non polar substances as Liquid petrolatum have negative [S] fail
to spread on water
o For organic acids, as Oleic acid,
the longer the carbon chain decrease in polar character decrease [S]
o Some oils can spread over water because they contain polar groups
as COOH and OH
Cohesive forces:
Benzene spreads on water not because it is polar but
because the cohesive forces between its molecules are much
weaker than the adhesion for water.
20. Application of Spreading coefficient in pharmacy
The requirement of film coats to be spreaded over the
tablet surfaces
The requirement of lotions with mineral oils to spread on
the skin by the addition of surfactants
21. Functional Classification
According to their pharmaceutical use, surfactants can be
divided into the following groups:
Wetting agents
Solubilizing agents
Emulsifying agents
Dispersing, Suspending and Defloculating agents
Foaming and antifoaming agents
Detergents
22. Wetting agents
Wetting agent is a surfactant that when dissolved in
water, lower the contact angle and aids in displacing the air
phase at the surface and replacing it with a liquid phase.
Solids will not be wetted if their critical surface tension
is exceeded than the surface tension of the liquid. Thus
water with a value of 72 dynes/cm will not wet polyethylene
with a critical surface tension of 3 1 dynes/cm.
Based on this concept we should expect a good wetting
agent to be one which reduces the surface tension of a liquid
to a value below the solid critical surface tension.
23. According to the nature of the liquid and the solid, a drop
of liquid placed on a solid surface will adhere to it or no. which is
the wettability between liquids and solids.
When the forces of adhesion are greater than the forces
of cohesion, the liquid tends to wet the surface and vice versa.
Place a drop of a liquid on a smooth surface of a solid. According
to the wettability, the drop will make a certain angle of contact
with the solid.
A contact angle is lower than 90°, the solid is called wettable
A contact angle is wider than 90°, the solid is named non-wettable.
A contact angle equal to zero indicates complete wettability.
25. The surface of liquid water (meniscus) has
a concave shape because water wets the
surface and creeps up the side
The surface of Mercury has a convex shape
it does not wet glass because the cohesive
forces within the drops are stronger than
the adhesive forces between the drops and
glass.
26. Micellar Solubilization
Surfactant molecules accumulate in the interfaces between
water and water insoluble compound. Their hydrocarbon
chains penetrate the outermost layer of insoluble compound
which combine with the water-insoluble molecules. Micelles
form around the molecules of the water-insoluble compound
inside the micelles’ cores and bring them into solution in an
aqueous medium. This phenomenon is called micellar
solubilization.
The inverted micelles formed by oil-soluble surfactant which
dissolves in a hydrocarbon solvent can solubilize water-soluble
compound which is located in the center of the micelle, out of
contact with the solvent.
27. Micelles of nonionic surfactants consist of an outer shell
containing their polyethylene glycol moieties mixed with
water and an inner core formed by their hydrocarbon
moieties. Some compounds like phenols and benzoic acid
form complexes with polyethylene glycols by hydrogen
bonding and/or are more soluble in liquids of intermediate
polarity like ethanol or ethyl ether than in liquids of low
polarity like aliphatic hydrocarbons. These compounds locate
in the aqueous polyethylene glycol outer shell of nonionic
micelles on solubilization.
Drugs which are soluble in oils and lipids can be
solubilized by micellar solubilization.
28. As Micellar solubilization depends on the existence of
micelles; it does not take place below the CMC. So
dissolution begins at the CMC. Above the CMC, the amount
solubilized is directly proportional to the surfactant
concentration because all surfactant added to the solution in
excess of the CMC exists in micellar form, and as the number
of micelles increases the extent of solubilization increases .
Compounds that are extensively solubilized increase the
size of micelles in two ways:
o The micelles swell because their core volume is
augmented by the volume of the solubilizate.
o The number of surfactant molecules per micelle
increases.
29. Foams are dispersion of a gas in a liquid
(liquid foams as that formed by soaps and
detergents ) or in a solid (solid foams as
sponges ).
Foaming and Anti Foaming agents
Foaming agents
Many Surfactants solutions promote the formation of foams
and stabilize them, in pharmacy they are useful in toothpastes
compositions.
Anti Foaming agents
They break foams and reduce frothing that may cause
problems as in foaming of solubilized liquid preparations. in
pharmacy they are useful in aerobic fermentations, steam
boilers.
30. Detergents
Detergents are surfactants used for removal of dirt.
Detergency involves:
•Initial wetting of the dirt and the surface to be
cleaned.
•Deflocculation and suspension, emulsification or
solubilisation of the dirt particles
•Finally washing away the dirt.
31. Structural Classification
A single surfactant molecule contains one or more
hydrophobic portions and one or more hydrophilic
groups.
According to the presence of ions in the surfactant
molecule they may be classified into:
Ionic surfactants
o Anionic surfactants: the surface active part is anion
(negative ion ) e.g. soaps, sodium lauryl sulfate
o Cationic surfactants: the surface active part is cation
(positive ion) e.g. quaternary ammonium salts
o Ampholytic surfactants: contain both positive and
negative ions e.g. dodecyl-B-alanine.
32. Ionic surfactants
They are the metal salts of long - chain fatty acids
as lauric acid.
Sodium dodecyl sulfate or Sodium Lauryl Sulfate is
used in toothpaste and ointments
Triethanolamine dodecyl sulfate is used in shampoos
and other cosmetic preparations.
Sodium dodecyl benzene sulfonate is a detergent and
has germicidal properties.
Sodium dialkvlsulfosuccinates are good wetting
agents.
Anionic surfactants
33. Cationic surfactants
These are chiefly quaternary ammonium compounds.
They have bacteriostatic activity probably because they
combine with the carboxyl groups in the cell walls and of
microorganisms by cation exchange, causing lysis.
Among the most popular antiseptics in this category are
benzalkonium chloride, cetylpyridinium chloride and
cetyltrimethylammonium bromide,
Ampholytic Surfactants
These are the least common, e.g. dodecyl-β-alanine
34. Non-ionic surfactants
Widely used in pharmaceutical formulations e.g.
Tweens, Spans, Brij and Myrj.
They are polyethylene oxide products.
Surfactants based on sorbitan are of pharmaceutical
importance.
Esterification of the primary hydroxyl group with
lauric, palmitic, stearic or oleic acid forms sorbitan
monolaurate, monopalmitate, monostearate or
monooleate
These are water-insoluble surfactants called Span 20,
40, 60 or 80, respectively.
Addition of about 20 ethylene oxide molecules
produces the water-soluble surfactants called
polysorbate or Tween 20, 40. 60 or 80.
35. At water-air interface
Surface-active molecules will
be adsorbed at water-air
interfaces and oriented so
that the hydrocarbon chains of are pushed out of the water and
rest on the surface, while the polar groups are inside the water.
Perhaps the polar groups pull the hydrocarbon chains partly into
the water.
At oil-water interface
Surface-active molecules will be oriented so that the hydrophobic
portion is inside the oil phase and the hydrophilic portion inside
the water phase.
As a Surface active substance contains a hydrophilic and a
hydrophobic portions, it is adsorbed as a monolayer at the
interfaces.
36. At low surfactant concentrations:
The hydrocarbon chains of surfactant molecules adsorbed
in the interface lie nearly flat oh the water surface.
At higher concentrations:
They stand upright because this permits more surfactant
molecules to pack into the interfacial monolayer.
As the number of surfactant molecules adsorbed at the
water-air interface increased, they tend to cover the water
with a layer of hydrocarbon chains. Thus, the water-air
interface is gradually transformed into an non polar-air
interface. This results in a decrease in the surface tension of
water.
37. At a given concentration, temperature, and salt content,
all micelles of a given surfactant usually contain the same
number of molecules, i.e. they are usually monodisperse.
For different surfactants in dilute aqueous solutions, this
number ranges approximately from 25 to 100 molecules.
The diameters of micelles are approximately between 30
and 80 Ao. Because of their ability to form aggregates of
colloidal size, surfactants are also called association
colloids.
Micelles are not permanent aggregates. They form and
disperse continually.
39. a- Cone-shaped surfactant resulting in b-normal micelles
c- Hampagne cork shaped surfactant resulting in d-reverse
micelles with control of their size by the water content
e- Interconnected cylinders .
f- Planar lamellar phase .
g- Onion-like lamellar phase.
Surfactant shapes in colloidal solution
40. Normal spherical micelles
In dilute aqueous solutions micelles are approximately spherical.
The polar groups of the surfactants are in the periphery and the
hydrocarbon chains are oriented toward the center, forming the
core of the micelles
Inverted spherical micelles
In solvents of low polarity or oils micelles are inverted.
The polar groups face inward to form the core of the micelle
while the hydrocarbon chains are oriented outward
Cylindrical and lamellar micelles
In more concentrated solutions
of surfactants, micelles change
from spherical either to cylindrical
or lamellar phase.
41. Nonionic surfactants have few incompatibilities with
drugs and are preferred over ionic surfactants. even in
formulations for external use, except when the
germicidal properties of cationic and anionic
surfactants are important.
Nonionic surfactants form weak complexes with
some preservatives as phenols, including esters of
p-hydroxybenzoic acid (Parabenzes) and with acids like
benzoic and salicylic via hydrogen bonds. This reduces
the antibacterial activity of these compounds.
Nonionic surfactants
42. Ionic surfactants
Ionic surfactants capable of reacting with compounds
possessing ions of the opposite charge. These reactions may
bind the surface active ions, sometimes with precipitation.
The compounds which react with the surface active ions are
also changed, and this may be harmful from the physiological
or pharmacological point of view.
Incompatibility of surface active quaternary ammonium
compounds with bentonite, kaolin, talc, and other solids
having cation exchange capacity.
44. Define the following terms:
[solid, liquid, gas, pure substance, compound, mixture, element, heterogeneous mixture, homogeneous mixture,
extensive properties, intensive properties, chemical properties, physical properties, density, color, texture,
conductivity, malleability, ductility, boiling point, melting point, flammability, corrosiveness, volatility, pounding,
tearing, cutting, dissolving, evaporating, fermenting, decomposing, Exothermic, endothermic, mass, density, gravity,
adhesive force, cohesive force, interface, adsorption, catalyst, dipole, physisorption, Chemisorption, hydrophilic,
hydrophobic, detergent, surfactant, surface tension, adsorbate, adsorbent, etc]
Respond to the following questions:
Give a descriptive account of the phases of matter with logical relevance to state of medicines as they are
taken for their respective therapeutical values
What is viscosity and its relation with fluids
What are surface and Inter-facial tension forces and respective association with activities of a substance
material with surface area
Describe some key phase changes of materials substance when exposed to some environmental conditions .
How is a chemical change different from a physical change at the surface of a material
What is contact angle of a substance and its significant role when two materials surface are in contact
Describe the role of contact angle during the wetting process of a material substance
What is a detergent and justified reasons for its variable composition
Differentiate the role of adsorption process of a material substance in surface and interfacial tension
State and explain the factors that have direct adsorptive effect on surface and interfacial tension process
Describe some practical applications of surface and interfacial tension process with some examples
What is the micelle made up of in terms of its physical form and shape
What are some of the practical uses of micellular material
State and explain some of the medical and pharmaceutical applications of named surface active agents.
45. Group work discussional questions:
Give a detailed descriptive account of functional classification of surface active agents
Give a detailed descriptive account of structural classification of surface active agents
Explain the process of micelle formation in a given favourable environment