An emulsion is a dispersion of one immiscible liquid within another. Emulsions are thermodynamically unstable but can exist in a metastable state. The stability of an emulsion depends on factors like interfacial tension, temperature, and entropy of mixing. Common emulsion types include water-in-oil and oil-in-water. Emulsifiers help stabilize emulsions by reducing interfacial tension and protecting newly formed droplets. Emulsion stability can be improved through techniques like charge stabilization, increasing viscosity, reducing droplet size, and using emulsifier blends or polymers at the interface.
This will help in find out the difference between micro and nano emulsions. Contain good explanations of their thermdynamic and kinetic stability also ternary phase diagram.
This will help in find out the difference between micro and nano emulsions. Contain good explanations of their thermdynamic and kinetic stability also ternary phase diagram.
Emulsification enables the pharmacist to prepare relatively stable and homogeneous mixtures of two immiscible liquids.
Emulsification enables the pharmacist to prepare relatively stable and homogeneous mixtures of two immiscible liquids.
Emulsions
Definition
These are homogenous, transparent and thermodynamically stable dispersion of water and oil stabilized by surfactant and co-surfactants
Consists of globules less than 0.1 μm in diameter
Types
Oil dispersed in water (o/w) - oil fraction low
Water dispersed in oil (w/o) - water fraction low
Bicontinuous (amount of oil and water are same)
Advantages
Thermodynamically stable, long shelf life
Potential reservoir of lipophilic or hydrophilic drug
Enhance the absorption and permeation of drugs through biological membranes
Increased solubility and stability of drugs
Ease and economical scale-up
Greater effect at lower concentration
Enhances the bioavailability of poorly soluble drugs
Theories of microemulsion
Interfacial or mixed film theory
Microemulsions are formed spontaneously due to formation of complex film at the interface by a mixture of surfactant and co-surfactant, As a result of which the interfacial tension reduces
Solubilization theory
Microemulsions are considered to be thermodynamically stable solutions of water swollen (w/o) or oil swollen (o/w) spherical micelles
Thermodynamic theory
The free energy of microemulsion formation is dependent on the role of surfactant in lowering the surface tension at the interface and increasing the entropy of the system
Multiple emulsions are complex polydispersed systems where both oil in water and water in oil emulsion exists simultaneously which are stabilized by lipophilic and hydrophilic surfactants respectively
The ratio of these surfactants is important in achieving stable multiple emulsions
They are also known as “Double emulsion” or “emulsion-within-emulsion”
Types
Oil-in-water-in-oil (O/W/O)
An o/w emulsion is dispersed in an oil continuous phase
Water-in-oil-in-water (W/O/W)
a w/o emulsion is dispersed in a water-continuous phase
MONOMOLECULAR ADSORPTION THEORY
MULTIMOLECULAR ADSORPTION THEORY
SOLID PARTICLE ADSORPTION THEORY
ELECTRICAL DOUBLE LAYER THEORY
ORIENTED WEDGE THEORY
Surfactants adsorb at the oil-water interface and form a monomolecular film
This film rapidly envelopes the droplets
They are very compact, elastic, flexible, strong and cannot be easily broken
For getting better stable emulsions combination of surfactants [surfactant blend] are used rather than a single one
The surfactant blend consists of both water soluble and oil soluble surfactants in order to approach the interface from aqueous and oil phase sides
At interface the surfactant blend interact to form a complex and condense a monomolecular film
Ex: A combination of Sodium cetyl sulfate (hydrophilic) and Cholesterol (lipophilic) forms a close packed complex film at the interface that produces an excellent emulsion
This document explains on emulsion and emulsifiers ad their application in industry. Emulsifiers are used in cosmetic, personal care, pharma preparations, food applications, paints, oilfiled applications, defoamers, agricultural applications and cleaning compositions
Introduction to Stability Testing of Drugs and Cosmetics. Includes the 3 types of stability test methods (Real time studies, Accelerated studies and Stress tests). Contains the WHO and ICH Climatic Zones for Real time, Intermediate and Accelerated tests). Classification of Packaging materials. Container- Closure Systems.
Biphasic system
emulsions
Classification of emulsion
Theories of emulsification
The HLB system
Stability of Emulsion
Emulsion Manufacturing
Test for emulsions
Pharmaceutical applications of emulsions
Packaging of emulsions
To prepare relatively stable and homogeneous mixtures of two immiscible liquids.
Permits administration of a liquid drug in the form of minute globules rather than in bulk.
Palatable administration of an otherwise distasteful oil by dispersing it in a sweetened, flavored aqueous vehicle.
Emulsification enables the pharmacist to prepare relatively stable and homogeneous mixtures of two immiscible liquids.
Emulsification enables the pharmacist to prepare relatively stable and homogeneous mixtures of two immiscible liquids.
Emulsions
Definition
These are homogenous, transparent and thermodynamically stable dispersion of water and oil stabilized by surfactant and co-surfactants
Consists of globules less than 0.1 μm in diameter
Types
Oil dispersed in water (o/w) - oil fraction low
Water dispersed in oil (w/o) - water fraction low
Bicontinuous (amount of oil and water are same)
Advantages
Thermodynamically stable, long shelf life
Potential reservoir of lipophilic or hydrophilic drug
Enhance the absorption and permeation of drugs through biological membranes
Increased solubility and stability of drugs
Ease and economical scale-up
Greater effect at lower concentration
Enhances the bioavailability of poorly soluble drugs
Theories of microemulsion
Interfacial or mixed film theory
Microemulsions are formed spontaneously due to formation of complex film at the interface by a mixture of surfactant and co-surfactant, As a result of which the interfacial tension reduces
Solubilization theory
Microemulsions are considered to be thermodynamically stable solutions of water swollen (w/o) or oil swollen (o/w) spherical micelles
Thermodynamic theory
The free energy of microemulsion formation is dependent on the role of surfactant in lowering the surface tension at the interface and increasing the entropy of the system
Multiple emulsions are complex polydispersed systems where both oil in water and water in oil emulsion exists simultaneously which are stabilized by lipophilic and hydrophilic surfactants respectively
The ratio of these surfactants is important in achieving stable multiple emulsions
They are also known as “Double emulsion” or “emulsion-within-emulsion”
Types
Oil-in-water-in-oil (O/W/O)
An o/w emulsion is dispersed in an oil continuous phase
Water-in-oil-in-water (W/O/W)
a w/o emulsion is dispersed in a water-continuous phase
MONOMOLECULAR ADSORPTION THEORY
MULTIMOLECULAR ADSORPTION THEORY
SOLID PARTICLE ADSORPTION THEORY
ELECTRICAL DOUBLE LAYER THEORY
ORIENTED WEDGE THEORY
Surfactants adsorb at the oil-water interface and form a monomolecular film
This film rapidly envelopes the droplets
They are very compact, elastic, flexible, strong and cannot be easily broken
For getting better stable emulsions combination of surfactants [surfactant blend] are used rather than a single one
The surfactant blend consists of both water soluble and oil soluble surfactants in order to approach the interface from aqueous and oil phase sides
At interface the surfactant blend interact to form a complex and condense a monomolecular film
Ex: A combination of Sodium cetyl sulfate (hydrophilic) and Cholesterol (lipophilic) forms a close packed complex film at the interface that produces an excellent emulsion
This document explains on emulsion and emulsifiers ad their application in industry. Emulsifiers are used in cosmetic, personal care, pharma preparations, food applications, paints, oilfiled applications, defoamers, agricultural applications and cleaning compositions
Introduction to Stability Testing of Drugs and Cosmetics. Includes the 3 types of stability test methods (Real time studies, Accelerated studies and Stress tests). Contains the WHO and ICH Climatic Zones for Real time, Intermediate and Accelerated tests). Classification of Packaging materials. Container- Closure Systems.
Biphasic system
emulsions
Classification of emulsion
Theories of emulsification
The HLB system
Stability of Emulsion
Emulsion Manufacturing
Test for emulsions
Pharmaceutical applications of emulsions
Packaging of emulsions
To prepare relatively stable and homogeneous mixtures of two immiscible liquids.
Permits administration of a liquid drug in the form of minute globules rather than in bulk.
Palatable administration of an otherwise distasteful oil by dispersing it in a sweetened, flavored aqueous vehicle.
aqueous one known as a direct emulsion. Stabilization of O/W emulsion is often performed with hydrophilic-hydrophobic particles. The hydrophilic end of the emulsifier molecule has an affinity for water, and the hydrophobic end is drawn to the fat/oil. Vigorously mixing the emulsifier with the water and oil creates a stable emulsion. For example, milk is oil in the water type of emulsion. In this mixture, fat globules are dispersed in the water.
Emulsion water in oil (W/O) is composed of an aqueous phase dispersed in the oil phase. A water-in-oil emulsion is much fattier than a direct emulsion. Margarine is a water-in-oil emulsion.
Other emulsions, such as oil in water in oil, or water in oil in water, exist as well. Blood is also an emulsion consisting of negatively charged colloidal particles, which are albuminoid substances.
Go to:
Issues of Concern
Emulsions are a sub-class of colloids, which are two-phase systems of matter.
Although the terms colloid and emulsion are sometimes used indistinctly, emulsion applies only when both dispersed, and continuous phases are liquids. A colloid is a mixture of a compound that is in a solid, liquid, or gas state and a liquid. The critical difference between a colloid and an emulsion is that colloid can form when any state of matter (solid, gas, or liquid) combine with a liquid. In contrast, the emulsion has two liquid components that are initially immiscible with each other.
Emulsions, as liquids, do not demonstrate a static internal structure. Emulsions are thermodynamically unstable as both the dispersed and continuous phases can revert as separate phases, oil, and water, by fusion or the coalescing of droplets. Industries use emulsifying agents, eg, surfactants, to maintain a static structure.[1]
Usually, the phase in which the surfactant exhibits the greatest solubility is the continuous phase. Thus, hydrophilic surfactants foster O/W emulsions, whereas lipophilic surfactants promote W/O emulsions.
Go to:
Clinical Significance
Emulsions are frequently used in pharmaceuticals, personal hygiene products, and cosmetics. These are usually oil and water emulsions, albeit dispersed. These emulsions are called creams, ointments, balms, pastes, films, or liquids, depending on their oil-to-water ratios, the addition of other additives, and their intended administration route. Emulsions allow the encapsulation of an active ingredient in the dispersed phase to protect it from degradation and preserve its activity in a sustained manner. They are used to make medications more palatable, to improve their effectiveness via dosage control of active ingredients, and to provide better aesthetics for topical drugs such as ointments.
Intravenous and parenteral emulsions may be used for nutritive therapy applications when a patient is unable to consume food or receive nutrition. Fat emulsions serve as dietary complements for patients who cannot get the required fat solely from their diet. The compound may be given as
Emulsion process and physical details of pharmaceuticalRubaetToha1
Demystifying Emulsions: A Journey into the World of Mixtures"
Brief Overview: Welcome to our SlideShare presentation on emulsions, a fascinating realm where oil and water come together in perfect harmony. Join us as we unravel the science, applications, and benefits of emulsions.
Slide 2: What Are Emulsions?
Definition: An emulsion is a colloidal dispersion of two immiscible liquids, typically oil and water, stabilized by an emulsifying agent.
Visual: Diagram showcasing the structure of emulsions with oil droplets dispersed in water and vice versa.
Slide 3: The Science Behind Emulsions
Key Concepts: Explore the principles of emulsification, including the role of emulsifiers, surfactants, and stability.
Visual: Molecular representation illustrating the interaction between emulsifying agents and oil-water interfaces.
Slide 4: Types of Emulsions
Classification: Overview of different emulsion types, such as oil-in-water (O/W) and water-in-oil (W/O), with examples.
Visual: Images representing common products for each type, like mayonnaise (O/W) and butter (W/O).
Slide 5: Emulsions in Everyday Life
Applications: Showcase how emulsions play a crucial role in various industries, including food, cosmetics, pharmaceuticals, and paints.
Visual: Collage of everyday products containing emulsions, from salad dressings to moisturizing creams.
Slide 6: Formulation and Stability
Factors Influencing Stability: Discuss the importance of formulation, temperature, pH, and shear forces in maintaining emulsion stability.
Visual: Graphs and charts depicting the impact of different factors on emulsion stability over time.
Slide 7: Challenges in Emulsion Technology
Common Issues: Address challenges like creaming, coalescence, and phase separation, along with strategies to overcome them.
Visual: Before-and-after images illustrating the effects of common challenges and successful solutions.
Slide 8: Innovations in Emulsion Science
Emerging Trends: Highlight recent advancements, such as nanoemulsions and green emulsifiers, shaping the future of emulsion technology.
Visual: Infographics showcasing cutting-edge developments in the field.
Slide 9: Conclusion
Key Takeaways: Summarize the essential points covered in the presentation.
Call to Action: Encourage the audience to explore further, experiment, and share their insights into the diverse world of emulsions.
Slide 10: Q&A and Discussion
Invite the audience to participate in a question-and-answer session, fostering engagement and collaboration.
Closing Note:
Thank your audience for their time and attention, and provide links or references for additional resources on emulsion science and applications.
Emulsions
Colloidal dispersion
Emulsifying agents
Surfactants
Stability
Oil-in-water (O/W)
Water-in-oil (W/O)
Formulation
Interfacial tension
Applications in food
Applications in cosmetics
Applications in pharmaceuticals
Applications in paints
Creaming
Coalescence
Phase separation
Nanoemulsions
Green emulsifiers
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.
This presentation explores a brief idea about the structural and functional attributes of nucleotides, the structure and function of genetic materials along with the impact of UV rays and pH upon them.
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.
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.
This pdf is about the Schizophrenia.
For more details visit on YouTube; @SELF-EXPLANATORY;
https://www.youtube.com/channel/UCAiarMZDNhe1A3Rnpr_WkzA/videos
Thanks...!
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.
Deep Behavioral Phenotyping in Systems Neuroscience for Functional Atlasing a...Ana Luísa Pinho
Functional Magnetic Resonance Imaging (fMRI) provides means to characterize brain activations in response to behavior. However, cognitive neuroscience has been limited to group-level effects referring to the performance of specific tasks. To obtain the functional profile of elementary cognitive mechanisms, the combination of brain responses to many tasks is required. Yet, to date, both structural atlases and parcellation-based activations do not fully account for cognitive function and still present several limitations. Further, they do not adapt overall to individual characteristics. In this talk, I will give an account of deep-behavioral phenotyping strategies, namely data-driven methods in large task-fMRI datasets, to optimize functional brain-data collection and improve inference of effects-of-interest related to mental processes. Key to this approach is the employment of fast multi-functional paradigms rich on features that can be well parametrized and, consequently, facilitate the creation of psycho-physiological constructs to be modelled with imaging data. Particular emphasis will be given to music stimuli when studying high-order cognitive mechanisms, due to their ecological nature and quality to enable complex behavior compounded by discrete entities. I will also discuss how deep-behavioral phenotyping and individualized models applied to neuroimaging data can better account for the subject-specific organization of domain-general cognitive systems in the human brain. Finally, the accumulation of functional brain signatures brings the possibility to clarify relationships among tasks and create a univocal link between brain systems and mental functions through: (1) the development of ontologies proposing an organization of cognitive processes; and (2) brain-network taxonomies describing functional specialization. To this end, tools to improve commensurability in cognitive science are necessary, such as public repositories, ontology-based platforms and automated meta-analysis tools. I will thus discuss some brain-atlasing resources currently under development, and their applicability in cognitive as well as clinical neuroscience.
(May 29th, 2024) Advancements in Intravital Microscopy- Insights for Preclini...Scintica Instrumentation
Intravital microscopy (IVM) is a powerful tool utilized to study cellular behavior over time and space in vivo. Much of our understanding of cell biology has been accomplished using various in vitro and ex vivo methods; however, these studies do not necessarily reflect the natural dynamics of biological processes. Unlike traditional cell culture or fixed tissue imaging, IVM allows for the ultra-fast high-resolution imaging of cellular processes over time and space and were studied in its natural environment. Real-time visualization of biological processes in the context of an intact organism helps maintain physiological relevance and provide insights into the progression of disease, response to treatments or developmental processes.
In this webinar we give an overview of advanced applications of the IVM system in preclinical research. IVIM technology is a provider of all-in-one intravital microscopy systems and solutions optimized for in vivo imaging of live animal models at sub-micron resolution. The system’s unique features and user-friendly software enables researchers to probe fast dynamic biological processes such as immune cell tracking, cell-cell interaction as well as vascularization and tumor metastasis with exceptional detail. This webinar will also give an overview of IVM being utilized in drug development, offering a view into the intricate interaction between drugs/nanoparticles and tissues in vivo and allows for the evaluation of therapeutic intervention in a variety of tissues and organs. This interdisciplinary collaboration continues to drive the advancements of novel therapeutic strategies.
Introduction:
RNA interference (RNAi) or Post-Transcriptional Gene Silencing (PTGS) is an important biological process for modulating eukaryotic gene expression.
It is highly conserved process of posttranscriptional gene silencing by which double stranded RNA (dsRNA) causes sequence-specific degradation of mRNA sequences.
dsRNA-induced gene silencing (RNAi) is reported in a wide range of eukaryotes ranging from worms, insects, mammals and plants.
This process mediates resistance to both endogenous parasitic and exogenous pathogenic nucleic acids, and regulates the expression of protein-coding genes.
What are small ncRNAs?
micro RNA (miRNA)
short interfering RNA (siRNA)
Properties of small non-coding RNA:
Involved in silencing mRNA transcripts.
Called “small” because they are usually only about 21-24 nucleotides long.
Synthesized by first cutting up longer precursor sequences (like the 61nt one that Lee discovered).
Silence an mRNA by base pairing with some sequence on the mRNA.
Discovery of siRNA?
The first small RNA:
In 1993 Rosalind Lee (Victor Ambros lab) was studying a non- coding gene in C. elegans, lin-4, that was involved in silencing of another gene, lin-14, at the appropriate time in the
development of the worm C. elegans.
Two small transcripts of lin-4 (22nt and 61nt) were found to be complementary to a sequence in the 3' UTR of lin-14.
Because lin-4 encoded no protein, she deduced that it must be these transcripts that are causing the silencing by RNA-RNA interactions.
Types of RNAi ( non coding RNA)
MiRNA
Length (23-25 nt)
Trans acting
Binds with target MRNA in mismatch
Translation inhibition
Si RNA
Length 21 nt.
Cis acting
Bind with target Mrna in perfect complementary sequence
Piwi-RNA
Length ; 25 to 36 nt.
Expressed in Germ Cells
Regulates trnasposomes activity
MECHANISM OF RNAI:
First the double-stranded RNA teams up with a protein complex named Dicer, which cuts the long RNA into short pieces.
Then another protein complex called RISC (RNA-induced silencing complex) discards one of the two RNA strands.
The RISC-docked, single-stranded RNA then pairs with the homologous mRNA and destroys it.
THE RISC COMPLEX:
RISC is large(>500kD) RNA multi- protein Binding complex which triggers MRNA degradation in response to MRNA
Unwinding of double stranded Si RNA by ATP independent Helicase
Active component of RISC is Ago proteins( ENDONUCLEASE) which cleave target MRNA.
DICER: endonuclease (RNase Family III)
Argonaute: Central Component of the RNA-Induced Silencing Complex (RISC)
One strand of the dsRNA produced by Dicer is retained in the RISC complex in association with Argonaute
ARGONAUTE PROTEIN :
1.PAZ(PIWI/Argonaute/ Zwille)- Recognition of target MRNA
2.PIWI (p-element induced wimpy Testis)- breaks Phosphodiester bond of mRNA.)RNAse H activity.
MiRNA:
The Double-stranded RNAs are naturally produced in eukaryotic cells during development, and they have a key role in regulating gene expression .
2. What is an emulsion?
• A dispersion of one or more immiscible liquid
phases in another, the distribution being in
the form of tiny droplets
3. What is an emulsion?
• Emulsions are metastable –from a
thermodynamic standpoint they can exist in a
form that is not the state of lowest energy
• Gibbs stated that “the only point in time
where an emulsion is stable, is when it is
completely separated”
4. Gibbs free energy equation
∆𝐺 = 𝛾𝐴 − 𝑇∆𝑆
ΔG is free energy of emulsification
γ is the interfacial tension
A is the interfacial area
T is temperature
ΔS is entropy of mixing
If ΔG is positive, the spontaneous emulsification is unlikely
If ΔG is negative, spontaneous emulsification will likely occur
The closer ΔG is to zero, the easier the formation of an
emulsion
6. Emulsion orientation
• The phase that is added tends to become the internal
phase
• The predominant solubility of the emulsifier tends to
determine the external phase (Bancroft’s rule)
• Generally, the phase of the greatest volume tends to
become the external phase
• The phase in which the stirrer is placed tends to become
the external phase
7. Identification of emulsion type
• Feel
• O/W emulsions tend to have a lighter feel than W/O
• Dispersibility
• Tested by dropping a small amount of emulsion in water –
O/W disperses easily while W/O remains whole
• Conductivity
• O/W emulsions conduct electricity well showing high levels
of conductance
• Dye penetration
• Water soluble dye is easily taken up in O/W system but not
in W/O
9. Microscopy
Uses
• Droplet size and size distribution
• Quality of manufacturing process e.g. undispersed
thickener
• Detecting unwanted crystallisation
• Early indications of instability e.g. flocculation,
coalescence, synerisis
• Comparison of different emulsions
• Liquid crystals
14. What is an emulsifier?
Water loving
head
Oil loving
tail
'Hydrophilic'
'Lipophobic'
'Lipophilic'
'Hydrophobic'
15. What is an emulsifier?
• An emulsifier is a surface active agent with an
affinity for both the oil and the water phases on
the same molecule
• An emulsifier reduces the surface tension at the
oil / water interface and protects the newly
formed droplet interfaces from immediate
coalescence
16. Droplet structures
Within a droplet structure the emulsifier forms
a monomolecular layer on the surface of the
droplet
The orientation of the emulsifier depends on
the type of emulsion formed
Oil - in - water
Water - in - oil
17. Improving emulsion stability
Clearly the ability of the emulsifier to completely cover
the surface area of the droplet will be dependent on;
• The concentration of emulsifier in the formulation
• The size of the emulsifier
• The size of the droplet
Good coverage is vital to ensure longer term stability
19. Types of emulsifiers - Anionic
Pros and Cons
• Were very common
• Old fashioned
• Not as versatile
• Cheap
• Limitations for actives due to high pH
• Give negative charge to the oil droplet
20. Types of emulsifiers
Cationic
The emulsifier carries a positive charge e.g.
Palmitamidopropyl Trimonium Chloride
_
ClCH3(CH2)14C NH(CH2)3
O
CH3
CH3
N CH3
+
21. Types of emulsifiers - Cationic
Pros and Cons
• Usage is not high in Skincare
• Good barrier
• Excellent silky skin feel
• Give positive charge to oil droplet
• Can be used at lower pH
22. Types of emulsifiers
Non-ionic
Emulsifier carries no overall charge and can be
made to form both Water-in-oil or Oil-in-water
emulsifiers e.g. Steareth-2
CH3 (CH2 )16 CH2 (OCH2 CH2)2 OH
23. Types of emulsifiers - Non-ionic
• Most common
• Wide range
• Versatile
• Strengthen the emulsion interface
• HLB system to predict choice
28. • Calculate the water loving portion of the surfactant on
a molecular weight percent basis and then divide that
number by 5
• Dividing by 5 keeps the HLB number scale limited to a
maximum of 20 which makes the scale smaller, thus a
bit more manageable
• Once calculated assign this number to the non-ionic
surfactant
• This assigned number is the HLB VALUE
Determining HLB value
Source: Croda presentation (Croda’s time saving guide to emulsifier selection)1
29. • Run a simple practical test based on nine small
experiments
• Materials needed for this test:
• an HLB “kit”
• about 200 grams of your oil
• eight small jars
• the instructions
• and a little bit of time (actually a lot of time!)
Determining HLB value
Source: Croda presentation (Croda’s time saving guide to emulsifier selection)1
31. • Look at your formula
• Determine which are the oil soluble ingredients
– this does not include the emulsifiers
• Weigh each of the weight percents of the oil phase ingredients
together and divide each by the total
• Multiply these answers times the required HLB of the individual
oils
• Add these together to get the required HLB of your unique
blend
Determining HLB value
Source: Croda presentation (Croda’s time saving guide to emulsifier selection)1
32. • A simple O/W lotion formula
• Mineral oil 8 %
• Caprylic/capric triglyceride 2 %
• Isopropyl isostearate 2 %
• Cetyl alcohol 4 %
• Emulsifiers 4 %
• Polyols 5 %
• Water soluble active 1 %
• Water 74 %
• Perfume q.s.
• Preservative q.s.
Determining HLB value
Source: Croda presentation (Croda’s time saving guide to emulsifier selection)1
34. Determining HLB value
Source: Croda presentation (Croda’s time saving guide to emulsifier selection)1
Oil phase
ingredient
contribution X required
HLB of
ingredient
equals
Mineral oil 50.0% 10.5 5.250
Caprylic cap.
Trig.
12.5% 5 0.625
Isopropyl
isostearate
12.5% 11.5 1.437
Cetyl alcohol 25.0% 15.5 3.875
Total 11.2
35. • Oil phase components can be given required HLB
values
• Required HLB and emulsifier HLB are matched up
• Each oil will have 2 required HLB’s, one for oil-in-water
emulsions, the other for water-in-oil emulsions
• The required HLB is published for some oils
Emulsifier selection using HLB
36. Emulsifier blends
In the HLB system the HLB of the emulsifier blend is
additive for example if an oil system had a required
HLB of 10 you could use either
Emulsifier
HLB 10
Emulsifier
HLB 5
Emulsifier
HLB 15or
37. Emulsifier blends
For a given blend of non-ionic emulsifiers, where
Emulsifier A is more lipophilic than Emulsifier B
Emulsifier A Emulsifier B
Oil Oil
Tighter packing
at interface
38. Considerations when choosing an
emulsifier
Type of emulsion
Oils to be emulsified
Processing - hot or cold
Effect on skin
Properties of the emulsion
Cost
Level of electrolyte
39. Potential irritation
• Emulsifiers, since they are surface
active, may be a factor in increasing the
risk of irritation
therefore
• Excessive levels of emulsifier should be
avoided
40. HLB Summary
• Pros
– Empirical system
giving starting
position
– Can be assessed
practically
• Cons
– Not good for anionics and
cationics
– Need to know HLB of oil
which can vary
– Can be time consuming
working out or measuring
– Does not determine the
amount of emulsifier
needed
42. Nothing can go wrong – can it?
• Emulsions are thermodynamically unstable
• This means that their natural tendency is to
revert to a state of least energy i.e. separated into
two layers
• The process of emulsification is to produce
droplets but also to maintain them in this state
over a reasonable shelf life
• Accelerated stability testing may reveal some of
the following horrors…
44. Factors that contribute to emulsion
instability
Forces of attraction between droplets
Gravity
Random movement of droplets
45. Creaming / Sedimentation
• No change in droplet size
• Reversible
• Driven by density difference
• Usually results from gravitational forces
Creaming Sedimentation
46.
47. Stokes’ Law
Defined as:-
Velocity of droplet (v) = (2a2 g (ρ1 – ρ2)) / 9η
Where
a = Radius of dispersed phase droplet
ρ1= Density of continuous (external) phase
ρ2 = Density of continuous (internal) phase
g = Acceleration due to gravity
η = viscosity of the continuous (external) phase
48. Coalescence
• Not reversible
• May lead from flocculation, creaming /
sedimentation or Brownian motion
• Involves 2 drops coming together
• May lead to complete separation
49. Coalescence
Coalescence increases if:-
• Fat or ice crystals present
• Viscosity of continuous phase is decreased
• Emulsion is agitated
• Interfacial viscosity is decreased
50. Van der Waals forces
Defined as
𝐹 = −
𝐴𝑎
12𝐻
Where
F = Van der Waals forces of attractions
A = Hamaker constant
a = Radius of dispersed phase droplets
H = Distance between two adjacent dispersed phase droplets
51. Improving emulsion stability
• Charge stabilisation
• Interfacial film strengthening
• with powders
• with polymers
• with non-ionic emulsifiers
• Steric stabilisation
• Continuous phase viscosity
• Droplet size
• Co-emulsifiers / polar waxes
• Liquid crystals
53. Improving Emulsion Stability
• In this system
• The negatively charged Stearate groups migrate to
the interface
• The positively charged Sodium ions in solution
(counter ions) are attracted to these now charged
droplets
• A layer is formed where the impact of the charge is
reduced
• This layer, called the Helmholtz double layer, can
reduce the repulsive effect and so stability
55. Improving Emulsion Stability
• The double layer is likely to be more diffuse the further
away from the droplet you go (Gouy and Chapman and
Stern)
• Can the same happen for cationic and non-ionic
emulsifiers?
• The effect is impacted by the presence of electrolytes
• Adding electrolyte increases instability by reducing the
shielding effect
• The extent of this depends on the amount of
electrolyte added and the valency of the electrolyte
56. Improving emulsion stability
• Interfacial film strengthening
• Reduces the probability of coalescence when
droplets collide
57. Interfacial film strengthening
• with powders
Powder particle size must be
very small
Powder must have an affinity for
both the oil and water phase
Improving emulsion stability
58. Interfacial film strengthening
• with polymers
Polymer sits at emulsion interface
Polar groups orient into the water phase
e.g. Cetyl PEG/PPG-10/1 Dimethicone
Acrylates/vinyl isodecanoate
crosspolymer
Improving emulsion stability
59. Interfacial film strengthening
• with non-ionic emulsifiers
Oil
Tighter packing
at interface
Interface strengthening is
dependent
on the number of molecules that
are packed into the interface
Improving emulsion stability
60. • Stabilises both oil-in-water and water-in-oil emulsions
through reducing interfacial forces
– Aids dispersion
– Reduces particle size
• Appropriate blends optimise stabilisation
– Reducing the energy imbalance
– Providing a barrier to coalescence
Interface stabilisation using non-ionic
emulsifiers
61. Steric stabilisation
• Polymer molecules adsorb on
the surface of oil droplets,
leaving tails and loops
extending into the water phase
• Polymer molecules must be
strongly adsorbed at interface
• There must be high coverage of
droplet surface with polymer
• The 'tails and loops' must be
soluble in the water phase
• e.g. Cetyl PEG/PPG-10/1
Dimethicone
62. • Continuous phase viscosity
• Thickening the water phase restricts
movement of oil droplets
• Thickeners with yield points are most
effective
• Droplet size
Increasing stability
Improving emulsion stability
63. • Co-emulsifiers / polar waxes
• e.g. Cetyl alcohol
• Co-emulsifiers have weaker surface activity
than primary emulsifiers
• Adds body and helps prevent coalescence
Improving emulsion stability
64. Stability testing -available tests
• Freeze thaw cycling
• Accelerated stability testing
• Tests at various temperatures
• Good guidance at www.ich.org
• Ultra centrifuge
• High speeds (>25,000 rpm) required
• Visual assessment
• As part of other techniques
• Use microscope
65. Stability testing
• Low shear evaluation
• Use sophisticated rheology machines
• Shake for several days
• Other tests as required
• Light
• Humidity
• Microbiological
66. Stability testing
Examining stability samples
Actual pack and clear container samples
Visual assessment in pack
Microscopic assessment
Viscosity, pH etc
68. How are emulsions formed?
In order to overcome the barrier between the oil
and water we need to add energy
This is derived from two sources:-
For long term stability both forms are needed
Chemical energy + Mechanical energy
(emulsifier) (homogeniser)
69. Two key requirements for creating
a stable emulsion
Apply enough energy to the two phases to
create a dispersion
Stabilise the created dispersion
Maintain a small droplet size
Increase the external phase viscosity to reduce
movement
Reduce phase density difference
70. Two stages of creating an emulsion
Stage 1 – apply energy to the two phases to
create a dispersion
Generally heat to 70 - 75°C
Stage 2 – stabilise the created dispersion
Maintain the small droplet size
Increase the external phase viscosity
Reduce phase density difference
71. Emulsion manufacture
Heating to this temperature can change the
level of the oil phase e.g. Cyclomethicone
If you need to add sensitive ingredients hot e.g.
sunscreens, then do it just prior to
emulsification
Watch out for tea breaks and shift changes and
build these into your considerations!
Avoid post emulsification addition of
preservatives etc that partition between oil and
water
72. Emulsion manufacture
After cooling the remaining ingredients are
added e.g. heat sensitive preservatives,
perfumes.
For W/O emulsions if you have to add
preservatives these MUST be added prior to
emulsification
Only Oil-in-water emulsions can be made to
weight easily
BUT you must start thinking about scale up
from the first formulation attempt
73. Emulsion manufacture
Laboratory
– Oil phase added with
Silverson mixing
– Beaker placed in
bowl of cold water
and stir cooled
Takes approx 15 min
Factory
– Oil phase added with
gate stirring followed
by homogeniser
mixing
Size and distance
– Cold water passed
through water jacket
with gate stirring
Takes hours!
76. Phase ratio
In simple terms the ratio of one phase to
another
BUT, in order to accurately describe the phase
ratio you need to know the type of emulsion
you are dealing with so
For an o/w emulsion a 30:70 ratio is 30% oil/
70% water
But for a w/o emulsion the opposite is true!
77. Phase inversion
It is possible to influence the orientation of an
emulsion in a number of ways including
Change the phase ratio of the emulsion
Influencing the behaviour of the emulsifier in the
emulsion
Phase inverted emulsions tend to have smaller
particle size and so improved chances of
longer term stability
Often used in wipes systems where low
viscosity is required
78. Phase inversion - phase ratio
In practical terms this could happen if
Phases are mixed opposite to convention
e.g. adding water to oil is expected to give a
water in oil emulsion but could give oil in
water
Deliberately making a water in oil emulsion
then adding water to increase the internal
phase and causing inversion e.g. low
energy emulsification
79. Phase Inversion Temperature
(PIT)
Occurs in some non-ionic emulsifier systems
Linked to solubility of emulsifier in the
respective phases
At different temperatures
In the presence of electrolyte
Mostly used to transition water in oil to oil in water
at a given temperature to produce desired small
particle size
80. Phase Inversion Temperature
(PIT)
Unique for any given emulsifier or blend of
emulsifiers
Useful for explaining behaviour of emulsion
systems
Helps to understand formation of differing types
of emulsion observed for a given blend of
emulsifiers
81. Phase Inversion Temperature
Within the marked band a complex three phase
mixture is found
Above TU a W/O emulsion exists, below TL O/W
This temperature and band will be different for
different systems
0o
75o
0 20% emulsifier blend
Temperatureo
C
TU
T
TL
2 phase
1 phase
2 phase
3 phase
Source: Kahlweit4
82. Phase Inversion Temperature
Why might this be the case?
Solubility of ethoxylated emulsifiers
increases with increasing ethoxylation
8 20
Solubility
Number of ethoxylate groups
83. Phase Inversion Temperature
Bancroft’s rule suggests that the emulsion
formed will depend on where the emulsifier is
most soluble
Oil in water where most water soluble (hydrophilic)
Water in Oil where most lipid soluble (lipophilic)
Consequently changes the effective HLB observed
By correct choice of emulsifier conversion from a
W/O to an O/W is possible
84. Emulsion rheology
Shear Deformation
• Shear deformation
• Is a change due to force
F being applied across
the top surface of area A.
• The ratio of force F to
area,A gives us a shear
stress across the liquid
• The liquid's response to
this applied shear stress
is to flow
85. Shear Deformation
Emulsion rheology
• Shear deformation
• The medium behaves as
a pack of cards
• At velocity V the liquid
spread and thins (T falls)
• It is this velocity gradient
that gives us the shear
rate
• Viscosity is simply the
ratio of the shear stress
to the shear rate
87. Thixotropy
Reduced viscosity when shear applied
Viscosity recovers when shear removed
Dilatancy
Increased viscosity when shear applied
May recover when shear removed
Shear thinning
Complete loss of viscosity when shear or
excess shear applied
Emulsion rheology
88. Emulsion rheology
• A detailed study can yield information about
• Predicted stability
• Flow
• during application
• during pumping
• time dependency
• effect of temperature on
91. Emulsion rheology
Observed rheology is linked to extent of
continuous phase
Large, major continuous phase/ small
dispersed phase
Properties similar to that of continuous
phase
Small continuous phase/ large dispersed
phase
Interparticle reactions more important
High resting viscosity observed
Exhibits yield point
92. Emulsion rheology
Electroviscous effect
The apparent increase in viscosity when
shear is applied to charged particles
Pulling charged particles between two others
requires greater force
-
-
-
93. Sources and further reading
1. “Croda’s time saving guide to emulsifier selection” - training course
available from Croda PLC
2. www.crodalubricants.com/download.aspx?s=133&m=doc&id=267
accessed 22 June 2009
3. Uniqema technology training document (unpublished)
4. Kahlweit M: Microemulsions, Science 29 April 1998, p671-621