Presentation include chapter solubility of drugs from second yr B-Pharm
Solubility, solubility expression, solute solvent interactions, solubility parameters, solvation and dissolution, factors affecting solubility, solubility of gases in liquids, liquids in liquids, fractional distillation, azeotropes, dissolution and drug release and diffusion.
PHYSICAL PHARMACEUTICS II COARSE DISPERSION VijayaKumarR28
R. VIJAYAKUMAR., M Pharm,
Research Scholar
department of Pharmaceutical Technology.
Anna university- BIT
Tiruchirappalli.
As per PCI syllabus for B Pharm / 2nd Year ,III Semester.
UNIT-III / Coarse dispersion
Tablets are solid dosage forms usually obtained by single or multiple compression of powders or granules. In certain cases tablets may be obtained by molding or extrusion techniques. They are uncoated or coated. Tablets are normally right circular solid cylinders, the end surfaces of which are flat or convex and the edges of which may be bevelled. They may have lines or break-marks (scoring), symbols or other markings.Tablets contain one or more active ingredients. They may contain excipients such as diluents, binders, disintegrating agents, glidants, lubricants, substances capable of modifying the behaviour of the dosage forms and the active ingredient(s) in the gastrointestinal tract, colouring matter authorized by the appropriate national or regional authority and flavouring substances. When such excipients are used it is necessary to ensure that they do not adversely affect the stability, dissolution rate, bioavailability, safety or efficacy of the active ingredient(s); there must be no incompatibility between any of the components of the dosage form.
Tablets are single-dose preparations intended for oral administration. Some are intended to be swallowed whole, some after being chewed and some after being crushed, some are intended to be dissolved or dispersed in water before being taken and some are intended to be retained in the mouth where the active ingredient(s) is/are liberated.
Solubility of Drugs (PHYSICAL PHARMACEUTICS-I)Rakesh Mishra
Solubility expressions, mechanisms of solute solvent interactions,solubility parameters, factors influencing
solubility of drugs, diffusion principles in biological systems, Raoult’s law, real solutions. Partially miscible
liquids(Phase equilibria, Phase rule, One , two and three component systems, ternary phase
diagram, Critical solution temperature and applications). Distribution law, its limitations and
applications
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
Suspension, interfacial properties of suspended particles, settling in suspensions, formulation of flocculated and deflocculated suspensions. Emulsions and theories of emulsification, microemulsion and multiple emulsions; Stability of emulsions, preservation of emulsions, rheological properties of emulsions.
A detailed study on every aspects of parenteral :- introduction, preformulation factors, essential requirements, vehicles and additives, isotonicity, production procedure, facilities, and controls, container and closure selection and finally the quality control evaluation of parenterals.
Presentation include chapter solubility of drugs from second yr B-Pharm
Solubility, solubility expression, solute solvent interactions, solubility parameters, solvation and dissolution, factors affecting solubility, solubility of gases in liquids, liquids in liquids, fractional distillation, azeotropes, dissolution and drug release and diffusion.
PHYSICAL PHARMACEUTICS II COARSE DISPERSION VijayaKumarR28
R. VIJAYAKUMAR., M Pharm,
Research Scholar
department of Pharmaceutical Technology.
Anna university- BIT
Tiruchirappalli.
As per PCI syllabus for B Pharm / 2nd Year ,III Semester.
UNIT-III / Coarse dispersion
Tablets are solid dosage forms usually obtained by single or multiple compression of powders or granules. In certain cases tablets may be obtained by molding or extrusion techniques. They are uncoated or coated. Tablets are normally right circular solid cylinders, the end surfaces of which are flat or convex and the edges of which may be bevelled. They may have lines or break-marks (scoring), symbols or other markings.Tablets contain one or more active ingredients. They may contain excipients such as diluents, binders, disintegrating agents, glidants, lubricants, substances capable of modifying the behaviour of the dosage forms and the active ingredient(s) in the gastrointestinal tract, colouring matter authorized by the appropriate national or regional authority and flavouring substances. When such excipients are used it is necessary to ensure that they do not adversely affect the stability, dissolution rate, bioavailability, safety or efficacy of the active ingredient(s); there must be no incompatibility between any of the components of the dosage form.
Tablets are single-dose preparations intended for oral administration. Some are intended to be swallowed whole, some after being chewed and some after being crushed, some are intended to be dissolved or dispersed in water before being taken and some are intended to be retained in the mouth where the active ingredient(s) is/are liberated.
Solubility of Drugs (PHYSICAL PHARMACEUTICS-I)Rakesh Mishra
Solubility expressions, mechanisms of solute solvent interactions,solubility parameters, factors influencing
solubility of drugs, diffusion principles in biological systems, Raoult’s law, real solutions. Partially miscible
liquids(Phase equilibria, Phase rule, One , two and three component systems, ternary phase
diagram, Critical solution temperature and applications). Distribution law, its limitations and
applications
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
Suspension, interfacial properties of suspended particles, settling in suspensions, formulation of flocculated and deflocculated suspensions. Emulsions and theories of emulsification, microemulsion and multiple emulsions; Stability of emulsions, preservation of emulsions, rheological properties of emulsions.
A detailed study on every aspects of parenteral :- introduction, preformulation factors, essential requirements, vehicles and additives, isotonicity, production procedure, facilities, and controls, container and closure selection and finally the quality control evaluation of parenterals.
Introduction
Definition
Features desired in pharmaceutical suspension
Advantage/Disadvantages of pharmaceutical suspension
Flocculated and deflocculated suspension
Interfacial properties of suspending particles
Settling in suspensions
Effect of Brownian movement,
Sedimentation of flocculated particles,
Sedimentation parameters
Formulation of suspensions
Wetting of Particles,
Controlled flocculation,
Flocculation in structured vehicle
Pharmaceutical Suspension, Coarse dispersion, Classification of dispersions, properties of coarse, colloidal and molecular dispersions
Thermodynamic and kinetic stability of dispersed systems
Electric Properties of Interfaces: Nernst and zeta potential, effect of electrolytes
Suspensions: DLVO theory, flocculated and deflocculated systems, controlled flocculation, physical stability of suspensions
The following presentation is only for quick reference. I would advise you to read the theoretical aspects of the respective topic and then use this presentation for your last minute revision. I hope it helps you..!!
Mayur D. Chauhan
Electro osmosis ,colligative propertries of colloids ,electrokinetic properti...Anand P P
electro osmosis.that topics deals with colloids and their one of the colligative properties that is electro kinetic property.under the electrokinetic colligative property of colloids consist 2 properties mainly electrophoresis and elecoosmosis.the electro osmosis have several application properties.the electroosmosis is mainly deals with the charge of colloidal system and their movements opposite charges.electrical double layer theory.
A pharmaceutical suspension is a coarse dispersion of insoluble solid particles in a liquid medium. ... However, it is difficult and also impractical to impose a sharp boundary between the suspensions and the dispersions having finer particles. Suspensions are an important class of pharmaceutical dosage forms
Zeta potential is a scientific term for electrokinetic potential (Zeta) in colloidal dispersions.
• Electrokinetic potential refers to a potential difference in a liquid characterizing electrochemical equilibrium on interfaces.
• Zeta potential is the charge that is located at the slipping point of a particle in the shear plane.
• Zeta potential is the Colloidal chemistry.
• It is usually denoted using the Greek letter zeta (ζ) hence ζ-potential.
• (ζ), is the potential difference between the dispersion medium and the stationary layer of fluid attached to the dispersed particle.
• Zeta Potential is the potential difference across an electrostatic double layer of ions that surround a solid particle dispersed in a polar liquid. In short, it is a measure of the surface charge of a particle.
• The electric potential at the boundary of the double layer is known as the Zeta potential of the particles and has values that typically range from +100 mV to - 100 mV
Download and play it my friends it contain VIDEO
The technique of ion exchange chromatography is based upon the interaction between charged solute molecules and oppositely charged moieties covalently linked to chromatographic matrix.
The reasons for its widespread success is its applicability, high resolving power, high capacity and simplicity of the technique.
Separation in ion exchange chromatography depends upon the reversible adsorption of charged solute molecules to immobilized ion exchange groups of opposite charge. Most experiments are performed by following : Video For Understanding Play It
surface & interfacial tension, surface free energy, Gibb’s equation, thermodynamic & kinetic stability of disperse systems
Definition, advantages and disadvantages, desirable features and pharmaceutical dispersions
Solubility of drugs: Solubility expressions, mechanisms of solute solvent interactions, ideal solubility parameters, solvation & association, quantitative approach to the factors
influencing solubility of drugs, diffusion principles in biological systems. Solubility
of gas in liquids, solubility of liquids in liquids, (Binary solutions, ideal solutions)
Raoult’s law, real solutions. Partially miscible liquids, Critical solution temperature . Distribution law, its limitations and applications
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
Explore the innovative world of trenchless pipe repair with our comprehensive guide, "The Benefits and Techniques of Trenchless Pipe Repair." This document delves into the modern methods of repairing underground pipes without the need for extensive excavation, highlighting the numerous advantages and the latest techniques used in the industry.
Learn about the cost savings, reduced environmental impact, and minimal disruption associated with trenchless technology. Discover detailed explanations of popular techniques such as pipe bursting, cured-in-place pipe (CIPP) lining, and directional drilling. Understand how these methods can be applied to various types of infrastructure, from residential plumbing to large-scale municipal systems.
Ideal for homeowners, contractors, engineers, and anyone interested in modern plumbing solutions, this guide provides valuable insights into why trenchless pipe repair is becoming the preferred choice for pipe rehabilitation. Stay informed about the latest advancements and best practices in the field.
Overview of the fundamental roles in Hydropower generation and the components involved in wider Electrical Engineering.
This paper presents the design and construction of hydroelectric dams from the hydrologist’s survey of the valley before construction, all aspects and involved disciplines, fluid dynamics, structural engineering, generation and mains frequency regulation to the very transmission of power through the network in the United Kingdom.
Author: Robbie Edward Sayers
Collaborators and co editors: Charlie Sims and Connor Healey.
(C) 2024 Robbie E. Sayers
CFD Simulation of By-pass Flow in a HRSG module by R&R Consult.pptxR&R Consult
CFD analysis is incredibly effective at solving mysteries and improving the performance of complex systems!
Here's a great example: At a large natural gas-fired power plant, where they use waste heat to generate steam and energy, they were puzzled that their boiler wasn't producing as much steam as expected.
R&R and Tetra Engineering Group Inc. were asked to solve the issue with reduced steam production.
An inspection had shown that a significant amount of hot flue gas was bypassing the boiler tubes, where the heat was supposed to be transferred.
R&R Consult conducted a CFD analysis, which revealed that 6.3% of the flue gas was bypassing the boiler tubes without transferring heat. The analysis also showed that the flue gas was instead being directed along the sides of the boiler and between the modules that were supposed to capture the heat. This was the cause of the reduced performance.
Based on our results, Tetra Engineering installed covering plates to reduce the bypass flow. This improved the boiler's performance and increased electricity production.
It is always satisfying when we can help solve complex challenges like this. Do your systems also need a check-up or optimization? Give us a call!
Work done in cooperation with James Malloy and David Moelling from Tetra Engineering.
More examples of our work https://www.r-r-consult.dk/en/cases-en/
Hybrid optimization of pumped hydro system and solar- Engr. Abdul-Azeez.pdffxintegritypublishin
Advancements in technology unveil a myriad of electrical and electronic breakthroughs geared towards efficiently harnessing limited resources to meet human energy demands. The optimization of hybrid solar PV panels and pumped hydro energy supply systems plays a pivotal role in utilizing natural resources effectively. This initiative not only benefits humanity but also fosters environmental sustainability. The study investigated the design optimization of these hybrid systems, focusing on understanding solar radiation patterns, identifying geographical influences on solar radiation, formulating a mathematical model for system optimization, and determining the optimal configuration of PV panels and pumped hydro storage. Through a comparative analysis approach and eight weeks of data collection, the study addressed key research questions related to solar radiation patterns and optimal system design. The findings highlighted regions with heightened solar radiation levels, showcasing substantial potential for power generation and emphasizing the system's efficiency. Optimizing system design significantly boosted power generation, promoted renewable energy utilization, and enhanced energy storage capacity. The study underscored the benefits of optimizing hybrid solar PV panels and pumped hydro energy supply systems for sustainable energy usage. Optimizing the design of solar PV panels and pumped hydro energy supply systems as examined across diverse climatic conditions in a developing country, not only enhances power generation but also improves the integration of renewable energy sources and boosts energy storage capacities, particularly beneficial for less economically prosperous regions. Additionally, the study provides valuable insights for advancing energy research in economically viable areas. Recommendations included conducting site-specific assessments, utilizing advanced modeling tools, implementing regular maintenance protocols, and enhancing communication among system components.
Student information management system project report ii.pdfKamal Acharya
Our project explains about the student management. This project mainly explains the various actions related to student details. This project shows some ease in adding, editing and deleting the student details. It also provides a less time consuming process for viewing, adding, editing and deleting the marks of the students.
Automobile Management System Project Report.pdfKamal Acharya
The proposed project is developed to manage the automobile in the automobile dealer company. The main module in this project is login, automobile management, customer management, sales, complaints and reports. The first module is the login. The automobile showroom owner should login to the project for usage. The username and password are verified and if it is correct, next form opens. If the username and password are not correct, it shows the error message.
When a customer search for a automobile, if the automobile is available, they will be taken to a page that shows the details of the automobile including automobile name, automobile ID, quantity, price etc. “Automobile Management System” is useful for maintaining automobiles, customers effectively and hence helps for establishing good relation between customer and automobile organization. It contains various customized modules for effectively maintaining automobiles and stock information accurately and safely.
When the automobile is sold to the customer, stock will be reduced automatically. When a new purchase is made, stock will be increased automatically. While selecting automobiles for sale, the proposed software will automatically check for total number of available stock of that particular item, if the total stock of that particular item is less than 5, software will notify the user to purchase the particular item.
Also when the user tries to sale items which are not in stock, the system will prompt the user that the stock is not enough. Customers of this system can search for a automobile; can purchase a automobile easily by selecting fast. On the other hand the stock of automobiles can be maintained perfectly by the automobile shop manager overcoming the drawbacks of existing system.
Water scarcity is the lack of fresh water resources to meet the standard water demand. There are two type of water scarcity. One is physical. The other is economic water scarcity.
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Courier management system project report.pdfKamal Acharya
It is now-a-days very important for the people to send or receive articles like imported furniture, electronic items, gifts, business goods and the like. People depend vastly on different transport systems which mostly use the manual way of receiving and delivering the articles. There is no way to track the articles till they are received and there is no way to let the customer know what happened in transit, once he booked some articles. In such a situation, we need a system which completely computerizes the cargo activities including time to time tracking of the articles sent. This need is fulfilled by Courier Management System software which is online software for the cargo management people that enables them to receive the goods from a source and send them to a required destination and track their status from time to time.
3. Definition
• Suspension is heterogeneous system and Suspension is
biphasic liquid dosage form.
• Dispersion medium is liquid and dispersion medium is solid
(suspension)
3
4. Features desired in Pharmaceutical Suspension
• Particles should settle slowly and should be readily
re-dispersed upon shaking of the container.
• The particle size of the suspensoid should remain
fairly constant throughout long periods of
undisturbed standing.
• The suspension should pour readily and evenly
from its container.
4
5. Applications of suspensions
• Drugs which degrade in aqueous solution may be suspended in a
non-aqueous phase. eg. Tetracycline hydrochloride is suspended
in a fractionated coconut oil for ophthalmic use.
• Lotions containing insoluble solids are formulated to leave a thin
coating of medicament on the skin. As the vehicle evaporates, it
gives a cooling effect and leaves the solid behind.eg calamine
lotion and sulphur lotion compound.
• Bulky, insoluble powders can be formulated as a suspension so
that they are easier to take eg Kaolin or chalk.
5
6. Advantages of suspensions
• Suspension can improve chemical stability of certain drug. E.g.
Procaine penicillin G
• Drug in suspension exhibits higher rate of bioavailability than
other dosage forms. bioavailability is in following order,
•
Solution > Suspension > Capsule > Compressed Tablet > Coated
tablet
• Duration and onset of action can be controlled. E.g. Protamine
Zinc-Insulin suspension
• Suspension can mask the unpleasant/ bitter taste of drug. E.g.
Chloramphenicol palmitate
6
7. Disadvantages of suspension
• Physical stability, sedimentation and compaction can causes
problems.
• It is bulky, therefore sufficient care must be taken during
handling and transport.
• It is difficult to formulate
• Uniform and accurate dose can not be achieved unless
suspension are packed in unit dosage form
7
8. Diffusible / in diffusible solid
1.DIFFUSIBLE SOLIDS– these sediment sufficiently slowly to enable
satisfactory dose removal after redispersion. eg. Light kaoline,
magnesium tricilicate
2.INDIFFUSIBLE SOLIDS- eg. sulphadimidine and chalk. These sediment
too rapidly and require the addition of other materials to reduce
sedimentation rate to an acceptable level.
8
9. Wetting phenomenon
• Force of attraction between solid and liquid play important role
• Angle of contact range (0° to 180 °)
10. Wetting phenomenon
• Contact angle is the angle between liquid droplet and surface over which it
spreads.
• Important action of wetting is to reduce angle of contact
11. Wetting phenomenon
Two types of solids
Lyophilic (wetting)
• Not sensitive to electrolytes in
medium
• Readily wettable
Lyophobic (non-wetting)
• Sensitive to electrolytes in
medium
• No aggregation
11
13. Strategies for wetting of hydrophobic solids
• Surfactant
• Hydrophilic polymers
• Water insoluble hydrophilic material (bentonite)
13
14. Methods to evaluate wetting property of
wetting agent
• Wet point method
• Amount of vehicle needed to just wet given amount of solid powder
• Flow point method
• Amount of liquid needed to produce pourability
• Unit (mL/100gm)
14
15. Methods to evaluate wetting property of
wetting agent
• Low wet point and low flow point
• Also, small difference between wet point and flow point
• This indicate good dispersion of solid particles in liquid medium.
15
17. Particle-particle interactions
(Zeta Potential)
Zeta potential is defined as the
difference in potential between the
surface of the tightly bound layer
(shear plane) and electroneutral
region of the solution.
17
18. Particle-particle interactions
• Thus electrostatic repulsion set up between adjacent particles
preventing them from adhering to one another.
• Accordingly deflocculation occurs.
• Solvation of particle surfaces also helps to prevent particles
coming together (Physical Barrier)
• Flocculation and deflocculation mechanism dependent on
the presence of surface electrical charges and the distribution
of ions around the particles
18
19. • At high electrolyte conc → Attractive force
predominate and cause coagulation
• At low electrolyte conc → Repulsive force
predominate
Particle-particle interactions
(Attractive forces vs Repulsive forces)
19
21. Interparticle forces
• Van der Waals attractive forces
• Electrostatic repulsive force → Overlapping of diffusion layer.
• Repulsive forces due to hydration → Structuring of water at interface
(Physical barrier)
• Steric repulsive force → Because of adsorbent (Physical barrier)
21
22. Electric double layer
• Regardless of the specific mechanism, the particles will bear either
positive or negative charges.
• Source of the charge on particle may arise from
- ionizable groups on the surfaces or
- adsorption of ions from the surrounding solution
23. 2020/9/19
Electric double layer
• Consider solid surface in contact with solution of electrolyte containing ions
• Some cations (+) adsorb on solid surface
• Adsorb ions that give charge to surface aa' (in this case cations +) known as
potential determining ions.
• Anions attracted to positive charge by electrical force of attraction known as
counter ions or gegenions .
• Shear plane is bb' rather than aa' because of tightly bound layer (next figure)
• First layer is aa' to bb'
• Second layer is bb' to cc'... more negative charge is present in this layer in this
case.
25. 2020/9/19
Nerst potential
• It is defined as potential difference between actual surface and
electro neutral region
• Potential at solid surface aa’ (above figure) due to potential
determining ions is known as Nerst potential
26. 2020/9/19
Zeta potential
• The zeta potential is defined as the difference in potential between
the surface of the tightly bound layer bb’ (shear plane) and electro-
neutral region of the solution.
• Zeta potential has practical application in the stability of systems
containing dispersed particles .
27. 2727
• If the zeta potential is reduced below a certain value, the attractive
forces exceed the repulsive forces, and the particles come together.
This phenomenon is known as flocculation
• The flocculated suspension is one in which zeta potential of particle
is -20 to +20 mV
• Thus the phenomenon of flocculation and deflocculation depends
on zeta potential carried by particles.
Zeta potential
28. 2020/9/19
• At low electrolyte conc → Repulsive
force predominate
• At high electrolyte conc → Repulsive
force reduce and cause coagulation
Effect of electrolytes
29. 2020/9/19
DLVO theory
• DLVO theory was developed in the 1940s and named after the
• Russian scientists
• B. Derjaguin
• L. Landau,
• Dutch scientists
• E. Verwey
• J. Overbeek
30. DLVO Theory
• It proposed that an energy barrier resulting from the electrostatic
repulsive force prevents two particles approaching one another and
adhering together.
• If the particles collide with sufficient energy to overcome the barrier, the
Van der Waals attractive force will attract them strongly and cause
them adhere together irreversibly.
• If the particles repel each other strongly, the dispersion will resist
coagulation and the dispersed system will be stable.
• If the repulsion is not sufficient then coagulation will take place.
33. Factors affecting repulsion between particles
which influences hydration of particles
• Electric (diffuse) double layer and its thickness
• Ionic strength (ionic concentration)
• Valency, size of ion on surface and in electric double layer
33
34. Swamping
• Increase in ionic strength (concentration of electrolytes) decreases
thickness of electric double layer .. This effect is known as swamping
• Swamping encourage aggregation
34
35. Schulze Hardy rule
• Specific adsorption of ion on solid neutralize surface charge and
allow aggregation
• Concentration of ion need to attain optimum aggregation of particles
depend upon type of interacting ion.
• Addition of more concentration beyond limit causes reversal of
charge → aggregation→ causes caking
• This effect is explained by ‘Schulze Hardy rule’
36. Schulze Hardy Rule
• Statement "valency of ion having charge opposit to that of
hydrophobic particle appears to determine the effectiveness
of the electrolyte in aggregating the particle"
• Aggregating value of ion increase with valency of ion
• Al+++ >> Fe++ >> Na+
• 1000 >>> 10 >> 1
36
37. Schulze Hardy Rule
• This rule is valid only for system in which there is no interaction
between electrolyte and ion of double layer of particle surface.
• Influence of valency of ion on aggregation of lyophobic particle can
be correlated to → Zeta potential and Sedimentation volume
• Hofmeister of lyotropic rule apply to hydrophilic particle
37
39. Classification of suspensions
• Based On General Classes
Oral suspension
Externally applied suspension
Parenteral suspension
• Based On Proportion Of Solid Particles
Dilute suspension (2 to10%w/v solid)
Concentrated suspension (50%w/v solid)
• Based On Electrokinetic Nature Of Solid Particles
Flocculated suspension
Deflocculated suspension
• Based On Size Of Solid Particles
Colloidal suspension (< 1 micron)
Coarse suspension (>1 micron)
Nano suspension (10 ng)
39
41. Types of suspension aggregates
Open Network
aggregate Close network aggregate
Deflocculated 41
42. 42
• In flocculated suspension, formed flocs (loose
aggregates) will cause increase in sedimentation rate
due to increase in size of sedimenting particles.
• Hence, flocculated suspensions sediment more
rapidly.
• Here, the sedimentation depends not only on the
size of the flocs but also on the porosity of flocs.
Flocculated Suspensions
43. Deflocculated suspensions
• In deflocculated suspension, individual particles
are settling.
• Rate of sedimentation is slow , which prevents
entrapping of liquid medium which makes it
difficult to re-disperse by agitation.
• This phenomenon called ‘caking’
• In deflocculated suspension larger particles settle
fast and smaller remain in supernatant liquid so
supernatant appears cloudy.
4343
44. Sedimentation
• This is a phenomenon which occurs in dispersed system where the
dispersed particles settle to the bottom of the container because of
gravitational force.
• This occurs because the particles are too large to remain
permanently suspended in the vehicle.
• Therefore suitable suspending agents are added to retard this
process.
44
45. Velocity of sedimentation
(Stoke’s Law of sedimentation)
V = D2 (ρ1-ρ2)/18η
• V= Velocity of sedimentation
• D= Diameter of particle
• ρ1 and ρ2 =Density of particle and liquid
• η = viscosity of liquid
• Pharmaceutical suspension containing less than 2% (w/v) of solid follow
Stoke’s Law.
• If solid content increase viscosity increases
45
46. Sedimentation Volume (F)
• Sedimentation volume is ratio of
ultimate height (height at time t) of
sediment to total height of suspension
when sedimentation occur in standard
condition
• F=Hu/Ho
• Higher value is desirable
46
48. F has values ranging from less than one to greater than one.
When F < 1 Vu < Vo
When F =1 Vu = Vo
The system (F =1) is said to be in flocculation equilibrium and
show no clear supernatant on standing.
When F > 1 Vu > Vo
Sediment volume is greater than the original volume due to the
network of flocs formed in the suspension and so loose and fluffy
sediment and extra vehicle is needed (added) to contain sediment
49. 49
Degree of flocculation (β)
"It is the ratio of the sedimentation volume of the flocculated
suspension ,F , to the sedimentation volume of the
deflocculated suspension, F∞ "
β = F / F∞
(Vu/Vo) flocculated
β = --------------------
(V∞/Vo) deflocculated
Vu
β = ------
V∞
The value of β is 1,when
flocculated suspension’s
sedimentation volume is
equal to the sedimentation
volume of deflocculated
suspension.
50. Need of Controlled Flocculation
• Assume powder is properly wetted and dispersed
• In order to prevent compact sediment (hard cake) we need
controlled flocculation
51. Controlled Flocculation
Controlled Flocculation can be achieved through following methods
• Effect of Electrolytes (ionic substance): It act as flocculating agents by
reducing electrical barrier between particles... by decresing zeta
potential and forming bridge between adjacent particles
• Effect of Surfactant
• Effect of Polymer
52. • At low electrolyte conc --Repulsive
force predominate
• At high electrolyte conc --
Repulsive force reduce and cause
coagulation
Effect of electrolytes
53. Effect of electrolytes
(Bismuth subnitrate suspension)
• Bismuth sub nitrate particles posses
+ve charge
• If we add monobasic potassium
phosphate (KH2PO4) then positive zeta
potential decrease to zero because of
adsorption of -ve phosphate ions then
increase in negative direction
• At certain +ve zeta potential, maximum
flocculation occur
• Onset of flocculation coincide with
maximum sedimentation volume
• When zeta potential become
sufficiently -ve repeptization
(deflocculation) occur once again and
sedimentation volume(F) falls
54. Effect of Surfactant
• Concentration of (cationic/anionic) surfactant as flocculating agent is
critical because--
• Act as wetting and deflocculating agent
• Surfactant improve dispersion by reducing surface tension
• Ionic surfactant (SLS) sometime cause flocculation
55. Effect of Polymers
• Hydrophilic polymer act as
protective colloids
• Act as flocculating agent
• Chain of polymer adsorb on
multiple particles
• Ex. Xanthan gum increase
sedimentation volume by
polymer-bridging phenomenon
for bismuth sub-carbonate
Fig. Dissolution and crystallization of drug in presence of polymer
56. Physical stability of suspensions
• Raising temperature leads to flocculation of sterically stabilized (by
non-ionic surfactant) suspension
• Repulsion force depend upon amount of surfactant adsorbed on
particles
• On heating, energy of repulsion reduces because of dehydration of
surfactant, attraction increases and particles flocculate
57. Physical stability of suspensions
• During freezing processes particle overcome repulsive barrier due to
ice formation.
• Particles come close enough and experience attractive force like in
primary minimum and form aggregates as per DLVO theory
• When ice melts, particles remain as aggregates unless work is applied
to overcome the primary energy peak
• Aggregate size is directly proportional to rate of freezing
59. Oswald Ripening
• Solubility of large crystal is less than that of smaller crystals
• It is because of more surface energy per unit mass on smaller
crystals.
• Smaller crystals are in a state of unstable equilibrium in a
supersaturated solution.
• As a result larger crystals grow on expense of the small crystals
59
60. What is Ostwald ripening?
• This is a spontaneous process that occurs because larger crystals are
more energetically (thermodynamically) favored than smaller
crystals.
• Large crystals, have lower energy state.
• While the formation of many small crystals is kinetically favored.
• Small crystals have a larger specific surface area (surface area to
volume ratio)
• Thus, many small crystals will attain a lower energy state by getting
transformed into large crystals and this is Ostwald ripening.
60
61. Ostwald ripening and crystal factors
• Fluctuation changes particle size
distribution in suspension.
• Particle growth is common if
solubility is temperature dependent.
• When temperature is high, small
particles dissolve to form saturated
solution.
• When temperature decreases, solute
deposit on large crystals hence →
crystal size increases for large size
crystals
62. Ostwald ripening and crystal factors
• Oswald ripening can be reduced by adding polymer or surfactant
• Polymer (PVP) segment adsorb on drug (e.g. acetaminophen)
• Hydration sheath present around polymer molecule
• Polymer inhibit approach of drug molecule from solution to crystal
surface for deposition
• High molecular wt. polymer (PVA) are more effective because of firm
adsorption on particle surface
63. Crystal structure factors
• No change in crystal habit (physical shape)
• Drug decomposition & Salting out
• pH change & change in particle size distribution
• Effect of temperature
• Change in crystal habit
• Solvation
• polymorphism
63
64. Effect of excipients on suspension stability
• Flocculation by sorbitol depend cloud point, thus lower the cloud point
less sorbitol needed to induce flocculation (cloud point can be lowered
by methyl paraben)
• (Cloud point is the temperature above which an aqueous solution of a
water-soluble surfactant becomes turbid)
• If low cloud point surfactant (low solubility) is used then less amount of
sorbitol is needed to induce flocculation
• Stability of suspension decrease because of interaction with excipients,
(preservative adsorption on particle)
• Amount of preservative (Benzalkonium Cl ) can change zeta potential
65. Rheology
• Viscosity is a measure of a fluid's resistance to flow.
• It describes the internal friction of a moving fluid.
• A fluid with large viscosity resists motion because its molecular
makeup gives it a lot of internal friction.
• A fluid with low viscosity flows easily because its molecular makeup
results in very little friction when it is in motion.
65
67. Rheology
Desirable
• Thixotrophy is a phenomenon or property exhibited by highly
floculated preparation in which a preparation is sem-solid at rest
(in the absence of shearing forces) but becomes fluid when
tapped or shaken and resumes its original structure after only a
few minutes of rest.
• A thixotropic suspension is the one which is viscous during
storage but loses consistency and become fluid upon shaking.
• A well-formulated thixotropic suspension would remain fluid long
enough for the easy dispense of a dose but would slowly regain
its original viscosity within a short time.
67
69. Rheology method
• To study structure achieved on
storage
• T-bar spindle with helipath
• T-bar continually descend to study
undisturbed sample
• Dial reading vs no. of turns of
spindle
69