Pharmaceutical dispersed systems consist of a dispersed particulate phase and a continuous dispersion medium. They are classified based on particle size as molecular, colloidal, or coarse dispersions. Colloidal systems exhibit optical properties like the Tyndall effect and light scattering. They demonstrate kinetic properties including Brownian motion, diffusion, and osmotic pressure. Colloidal particles often carry an electric charge, forming an electric double layer that can electrostatically stabilize the system. The physical stability of colloids depends on a balance of electrical repulsive forces and attractive van der Waals forces between particles.
This document discusses an introduction to rheology and its importance in pharmacy. It begins by outlining the topics to be covered, which include the importance of rheology in pharmacy applications, definitions and fundamentals, types of fluids, viscosity, measurements of viscosity, instrumentation, and viscoelasticity. The first section defines rheology and describes its importance in areas like manufacturing dosage forms, handling drugs for administration, topical applications, and more. The introduction provides definitions of key terms like shear stress and rate of shear. It also describes Newton's laws of viscous flow. The document goes on to classify fluids as Newtonian or non-Newtonian and describes different types of non-Newtonian fluids.
This document provides information about pharmaceutical suspensions. It begins by defining a suspension as a disperse system where an insoluble solid internal phase is uniformly dispersed throughout an external liquid phase. Particle size is important for suspensions to be classified as coarse or colloidal. Suspensions differ from solutions in that particles remain dispersed rather than dissolving. Sedimentation occurs over time due to particle size and density. Suspending agents are added to prevent sedimentation by increasing viscosity. The document discusses formulation, applications, advantages, and disadvantages of suspensions.
This document discusses various techniques to improve the solubility of poorly soluble drugs, which is important for developing effective dosage forms and achieving desired drug concentrations. It defines solubility and discusses the importance of solubility in drug development. Some key techniques covered are co-solvency, use of surfactants, solid dispersions, complexation, changing temperature, hydrotropy, polymorphism, amorphous forms, solvates, salt formation, and micronization/nanonization. The goal is to select the optimal method for a given drug to enhance dissolution and absorption.
1) Solubility is the maximum amount of a substance that dissolves in a solvent to form a saturated solution at a given temperature and pressure.
2) Solubility is ideally measured at 4°C and 37°C to ensure physical stability and support biopharmaceutical evaluation. Solubility below 1 mg/ml indicates poor absorption and need for preformulation studies.
3) Preformulation solubility studies focus on the drug solvent system and include determining properties like intrinsic solubility, pH solubility profiles, effects of surfactants, and temperature dependence to understand a drug's solubility and dissolution behavior.
This document discusses dispersed systems such as emulsions, colloids, and suspensions. It begins by defining dispersed systems as particulate matter distributed throughout a continuous medium and classifies them based on particle size into molecular, colloidal, or coarse dispersions. The document then covers topics such as interfacial phenomenon, wetting, adsorption, surface active agents, micellar solubilization, and the use of these concepts in pharmacy. It provides details on emulsions, including the theories of emulsification, methods to determine emulsion type, emulsifying agents, and emulsion stability.
The document discusses various factors that affect solubility. It defines solubility and explains how the solubility of a substance depends on the solvent, temperature, and pressure. Temperature generally increases the solubility of salts but can decrease it for substances like calcium hydroxide. Particle size and molecular structure modifications can also impact solubility. Common ion, complex formation, surfactants, pH, and non-electrolyte addition are additional factors covered. Solubility of gases depends on pressure and temperature based on Henry's law.
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
This document discusses an introduction to rheology and its importance in pharmacy. It begins by outlining the topics to be covered, which include the importance of rheology in pharmacy applications, definitions and fundamentals, types of fluids, viscosity, measurements of viscosity, instrumentation, and viscoelasticity. The first section defines rheology and describes its importance in areas like manufacturing dosage forms, handling drugs for administration, topical applications, and more. The introduction provides definitions of key terms like shear stress and rate of shear. It also describes Newton's laws of viscous flow. The document goes on to classify fluids as Newtonian or non-Newtonian and describes different types of non-Newtonian fluids.
This document provides information about pharmaceutical suspensions. It begins by defining a suspension as a disperse system where an insoluble solid internal phase is uniformly dispersed throughout an external liquid phase. Particle size is important for suspensions to be classified as coarse or colloidal. Suspensions differ from solutions in that particles remain dispersed rather than dissolving. Sedimentation occurs over time due to particle size and density. Suspending agents are added to prevent sedimentation by increasing viscosity. The document discusses formulation, applications, advantages, and disadvantages of suspensions.
This document discusses various techniques to improve the solubility of poorly soluble drugs, which is important for developing effective dosage forms and achieving desired drug concentrations. It defines solubility and discusses the importance of solubility in drug development. Some key techniques covered are co-solvency, use of surfactants, solid dispersions, complexation, changing temperature, hydrotropy, polymorphism, amorphous forms, solvates, salt formation, and micronization/nanonization. The goal is to select the optimal method for a given drug to enhance dissolution and absorption.
1) Solubility is the maximum amount of a substance that dissolves in a solvent to form a saturated solution at a given temperature and pressure.
2) Solubility is ideally measured at 4°C and 37°C to ensure physical stability and support biopharmaceutical evaluation. Solubility below 1 mg/ml indicates poor absorption and need for preformulation studies.
3) Preformulation solubility studies focus on the drug solvent system and include determining properties like intrinsic solubility, pH solubility profiles, effects of surfactants, and temperature dependence to understand a drug's solubility and dissolution behavior.
This document discusses dispersed systems such as emulsions, colloids, and suspensions. It begins by defining dispersed systems as particulate matter distributed throughout a continuous medium and classifies them based on particle size into molecular, colloidal, or coarse dispersions. The document then covers topics such as interfacial phenomenon, wetting, adsorption, surface active agents, micellar solubilization, and the use of these concepts in pharmacy. It provides details on emulsions, including the theories of emulsification, methods to determine emulsion type, emulsifying agents, and emulsion stability.
The document discusses various factors that affect solubility. It defines solubility and explains how the solubility of a substance depends on the solvent, temperature, and pressure. Temperature generally increases the solubility of salts but can decrease it for substances like calcium hydroxide. Particle size and molecular structure modifications can also impact solubility. Common ion, complex formation, surfactants, pH, and non-electrolyte addition are additional factors covered. Solubility of gases depends on pressure and temperature based on Henry's law.
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
This document provides an overview of suspension theory. Key points include:
- A suspension is a dispersion of insoluble solid particles in a liquid medium, with particle sizes generally greater than 0.1μm.
- Particle characteristics like size, shape, surface properties, and electrical charges influence interactions and stability.
- Attractive van der Waals forces can cause flocculation while repulsive electrical double layer forces promote stability, as described by the DLVO theory.
- Additives are often needed to control particle interactions and maintain long-term stability of the suspension.
This document discusses stability factors and applications of pharmaceutical suspensions. It notes that small particle size, increasing viscosity, and maintaining optimal temperature contribute to suspension stability. Suspensions are used for insoluble drugs, to improve drug stability, and to mask unpleasant tastes. Key factors for stability include particle size, viscosity, temperature, surfactants, hydrophilic colloids, solvents, and proper mixing procedures.
This document provides information about pharmaceutical suspensions. It defines a suspension as a coarse dispersion where an insoluble solid active ingredient is uniformly dispersed throughout an external aqueous or non-aqueous liquid phase. Suspensions are formulated when drugs are insoluble, to mask bitter tastes, increase stability, or achieve sustained release. Key factors in formulating stable suspensions include particle size, shape, wettability, and use of suspending agents to decrease interparticle attraction and impart viscosity. Proper manufacturing controls suspension quality.
Physical pharmacy i third semester (unit-i) solubility of drugMs. Pooja Bhandare
Physical pharmaceutics is the study of physicochemical properties of drug molecules in designing dosage forms. This document discusses the definitions and concepts related to solubility of drugs. It defines key terms like solute, solvent, saturated solution, and explains how solubility is expressed quantitatively and qualitatively. The mechanisms of solute-solvent interactions are discussed based on the nature of solvents being polar, non-polar or semi-polar. Specific examples are provided to illustrate solubility principles for different classes of solvents.
This document provides an overview of disperse systems, including emulsions and suspensions. It discusses key concepts such as interfacial phenomena, wetting, adsorption, surfactants, and micelle formation. Theories of emulsification including electric double layer, phase volume, oriented wedge, and surface tension are presented. Methods for determining emulsion type including dilution, dye, conductivity, and fluorescence tests are described. Emulsifying agents and factors influencing emulsion stability are also summarized. Suspensions are defined as biphasic systems with solid particles between 0.5-5 microns dispersed in a liquid. Particle size and sedimentation theories are briefly covered.
Solubility enhancement by using various techniques Prajakta Chavan
This document discusses various techniques for enhancing the solubility of drugs, including particle size reduction, hydrotropy, cosolvency, solubilization by surfactants, solid dispersions, pH adjustment, high pressure homogenization, supercritical fluid recrystallization, sonocrystallization, complexation, spray drying, inclusion complex formation, liquisolid technique, microemulsions, and self-emulsifying drug delivery systems. Particle size reduction techniques like micronization and nanosuspensions increase surface area to enhance dissolution rate and solubility. Other techniques utilize excipients like surfactants, cosolvents, and polymers to solubilize drugs.
State of matter and properties of matter (Part-3) (Eutectic mixture)Ms. Pooja Bhandare
This document discusses eutectic mixtures, which are mixtures of two or more phases that have the lowest melting point. A eutectic mixture is formed at a specific composition where the phases simultaneously crystallize from a molten solution. The term comes from the Greek word meaning "easily melted". Eutectic mixtures can be formed between APIs, APIs and excipients, or excipients. Below the eutectic temperature, the mixture exists as a solid, while above it exists as a liquid. Eutectic mixtures have various applications in the pharmaceutical industry, such as improving drug solubility and bioavailability for different routes of administration like oral, transdermal, parental, and nasal delivery.
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 :
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
The document discusses various methods to improve drug solubility including physical modifications like particle size reduction through micronization or formation of nanosuspensions, modification of crystal habit through polymorphism, and drug dispersion in carriers through techniques like solid dispersions. It also discusses chemical modifications such as changing pH, use of buffers, and derivatization. Other methods covered are complexation, solubilization by surfactants to form microemulsions, co-crystallization, cosolvency, hydrotrophy, and solvent deposition. The biopharmaceutical classification system relating solubility and permeability to drug absorption is also summarized.
This document summarizes a seminar on colloidal dispersions presented by Sayani Saha. It defines colloidal dispersions as systems with a dispersed particle phase and continuous dispersion medium between 1-1000 nm. Dispersions are classified by size as molecular, colloidal, or coarse dispersions. The properties of colloidal sols are discussed, including how they are lyophilic or lyophobic, how particles are solvated, how they are prepared, and how they are affected by electrolytes. Various shapes of colloidal particles and classifications based on dispersion medium and phase are also summarized. The document concludes with brief discussions of coacervation and peptization processes.
Suspension are biphasic liquids dosage form in which insoluble solid particulate are uniformly distributed in liquid phase which may be stabilized by inclusion of suspending agents.
The document discusses suspensions, which are heterogeneous systems with small, solid particles dispersed throughout a liquid medium. Suspensions can be used orally, parenterally, or externally. They are divided into coarse and colloidal suspensions based on particle size. Various factors including particle size and distribution, viscosity, and stability must be considered for suspension formulation and production. Common methods for preparing suspensions involve using mortar and pestle or mixing equipment depending on the materials used.
Suspension is made of two phase system, consisting of a finely divided solid particles (Dispersed phase) distributed in a particular manner throughout another medium (Continuous phase).
This document discusses different methods for determining the pKa value of drugs. It begins by defining pKa as the negative base 10 logarithm of acid dissociation constant of a solution. It then describes several common methods for determining pKa, including UV-metric, pH-metric, and potentiometric titration methods. The pH-metric method involves titrating a drug solution and calculating pKa based on fitting the measured pH curve. Potentiometric titration plots the change in potential versus reagent volume added, with the inflection point used to determine pH and thus pKa. Understanding pKa is important for solubility and drug absorption properties.
This document provides an overview of drug stability for a pharmaceutical chemistry and pharmaceutics course. It defines drug stability as the ability of a dosage form to maintain its physical, chemical, therapeutic, and microbial properties during storage and usage. It discusses factors that influence stability such as temperature, pH, moisture, light, and packaging. It also describes different types of instability like physical changes, chemical degradation through hydrolysis, oxidation, or isomerization, and microbial contamination. The document aims to help predict and ensure drug stability.
1) An emulsion is an unstable mixture of two immiscible liquids, where one liquid is dispersed as globules in the other liquid. Emulsions can be O/W (oil in water) or W/O (water in oil) types.
2) Pharmaceutical emulsions are used to deliver unpleasant tasting drugs, provide slow release of water-soluble drugs, and enhance absorption of oil-soluble drugs.
3) The key steps in formulating an emulsion are selecting an emulsifying agent based on its HLB value, adding preservatives and antioxidants, and using methods like trituration or the bottle method to prepare the emulsion.
The document provides information about short term training conducted at Oniosome Healthcare Pvt. Ltd., including topics covered such as calibration of glassware, determination of melting point and solubility of drugs, determination of hydrophilic-lipophilic balance (HLB) value, thin layer chromatography, high performance liquid chromatography, friability, dissolution, disintegration, and UV spectroscopy. It then discusses the definition of HLB value, how it indicates the polarity of surfactant molecules on a scale of 1-40, and how lipophilic and hydrophilic portions of surfactant molecules affect oil and water solubility. Finally, it outlines methods for determining HLB values and requirements, and applications of surfactants based
1. The document discusses colloidal dispersions, which are systems where particles between 1 nm and 1000 nm are dispersed uniformly throughout a dispersion medium.
2. Colloidal systems are classified based on particle size into molecular dispersions, colloidal dispersions, and coarse dispersions. They are also classified based on particle-medium interactions into lyophilic, lyophobic, and association colloids.
3. The key properties of colloidal systems discussed are electrical properties (surface charge, zeta potential, electrophoresis), optical properties (Tyndall effect, turbidity), and kinetic properties (Brownian motion, diffusion, viscosity).
This document provides an overview of suspension theory. Key points include:
- A suspension is a dispersion of insoluble solid particles in a liquid medium, with particle sizes generally greater than 0.1μm.
- Particle characteristics like size, shape, surface properties, and electrical charges influence interactions and stability.
- Attractive van der Waals forces can cause flocculation while repulsive electrical double layer forces promote stability, as described by the DLVO theory.
- Additives are often needed to control particle interactions and maintain long-term stability of the suspension.
This document discusses stability factors and applications of pharmaceutical suspensions. It notes that small particle size, increasing viscosity, and maintaining optimal temperature contribute to suspension stability. Suspensions are used for insoluble drugs, to improve drug stability, and to mask unpleasant tastes. Key factors for stability include particle size, viscosity, temperature, surfactants, hydrophilic colloids, solvents, and proper mixing procedures.
This document provides information about pharmaceutical suspensions. It defines a suspension as a coarse dispersion where an insoluble solid active ingredient is uniformly dispersed throughout an external aqueous or non-aqueous liquid phase. Suspensions are formulated when drugs are insoluble, to mask bitter tastes, increase stability, or achieve sustained release. Key factors in formulating stable suspensions include particle size, shape, wettability, and use of suspending agents to decrease interparticle attraction and impart viscosity. Proper manufacturing controls suspension quality.
Physical pharmacy i third semester (unit-i) solubility of drugMs. Pooja Bhandare
Physical pharmaceutics is the study of physicochemical properties of drug molecules in designing dosage forms. This document discusses the definitions and concepts related to solubility of drugs. It defines key terms like solute, solvent, saturated solution, and explains how solubility is expressed quantitatively and qualitatively. The mechanisms of solute-solvent interactions are discussed based on the nature of solvents being polar, non-polar or semi-polar. Specific examples are provided to illustrate solubility principles for different classes of solvents.
This document provides an overview of disperse systems, including emulsions and suspensions. It discusses key concepts such as interfacial phenomena, wetting, adsorption, surfactants, and micelle formation. Theories of emulsification including electric double layer, phase volume, oriented wedge, and surface tension are presented. Methods for determining emulsion type including dilution, dye, conductivity, and fluorescence tests are described. Emulsifying agents and factors influencing emulsion stability are also summarized. Suspensions are defined as biphasic systems with solid particles between 0.5-5 microns dispersed in a liquid. Particle size and sedimentation theories are briefly covered.
Solubility enhancement by using various techniques Prajakta Chavan
This document discusses various techniques for enhancing the solubility of drugs, including particle size reduction, hydrotropy, cosolvency, solubilization by surfactants, solid dispersions, pH adjustment, high pressure homogenization, supercritical fluid recrystallization, sonocrystallization, complexation, spray drying, inclusion complex formation, liquisolid technique, microemulsions, and self-emulsifying drug delivery systems. Particle size reduction techniques like micronization and nanosuspensions increase surface area to enhance dissolution rate and solubility. Other techniques utilize excipients like surfactants, cosolvents, and polymers to solubilize drugs.
State of matter and properties of matter (Part-3) (Eutectic mixture)Ms. Pooja Bhandare
This document discusses eutectic mixtures, which are mixtures of two or more phases that have the lowest melting point. A eutectic mixture is formed at a specific composition where the phases simultaneously crystallize from a molten solution. The term comes from the Greek word meaning "easily melted". Eutectic mixtures can be formed between APIs, APIs and excipients, or excipients. Below the eutectic temperature, the mixture exists as a solid, while above it exists as a liquid. Eutectic mixtures have various applications in the pharmaceutical industry, such as improving drug solubility and bioavailability for different routes of administration like oral, transdermal, parental, and nasal delivery.
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 :
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
The document discusses various methods to improve drug solubility including physical modifications like particle size reduction through micronization or formation of nanosuspensions, modification of crystal habit through polymorphism, and drug dispersion in carriers through techniques like solid dispersions. It also discusses chemical modifications such as changing pH, use of buffers, and derivatization. Other methods covered are complexation, solubilization by surfactants to form microemulsions, co-crystallization, cosolvency, hydrotrophy, and solvent deposition. The biopharmaceutical classification system relating solubility and permeability to drug absorption is also summarized.
This document summarizes a seminar on colloidal dispersions presented by Sayani Saha. It defines colloidal dispersions as systems with a dispersed particle phase and continuous dispersion medium between 1-1000 nm. Dispersions are classified by size as molecular, colloidal, or coarse dispersions. The properties of colloidal sols are discussed, including how they are lyophilic or lyophobic, how particles are solvated, how they are prepared, and how they are affected by electrolytes. Various shapes of colloidal particles and classifications based on dispersion medium and phase are also summarized. The document concludes with brief discussions of coacervation and peptization processes.
Suspension are biphasic liquids dosage form in which insoluble solid particulate are uniformly distributed in liquid phase which may be stabilized by inclusion of suspending agents.
The document discusses suspensions, which are heterogeneous systems with small, solid particles dispersed throughout a liquid medium. Suspensions can be used orally, parenterally, or externally. They are divided into coarse and colloidal suspensions based on particle size. Various factors including particle size and distribution, viscosity, and stability must be considered for suspension formulation and production. Common methods for preparing suspensions involve using mortar and pestle or mixing equipment depending on the materials used.
Suspension is made of two phase system, consisting of a finely divided solid particles (Dispersed phase) distributed in a particular manner throughout another medium (Continuous phase).
This document discusses different methods for determining the pKa value of drugs. It begins by defining pKa as the negative base 10 logarithm of acid dissociation constant of a solution. It then describes several common methods for determining pKa, including UV-metric, pH-metric, and potentiometric titration methods. The pH-metric method involves titrating a drug solution and calculating pKa based on fitting the measured pH curve. Potentiometric titration plots the change in potential versus reagent volume added, with the inflection point used to determine pH and thus pKa. Understanding pKa is important for solubility and drug absorption properties.
This document provides an overview of drug stability for a pharmaceutical chemistry and pharmaceutics course. It defines drug stability as the ability of a dosage form to maintain its physical, chemical, therapeutic, and microbial properties during storage and usage. It discusses factors that influence stability such as temperature, pH, moisture, light, and packaging. It also describes different types of instability like physical changes, chemical degradation through hydrolysis, oxidation, or isomerization, and microbial contamination. The document aims to help predict and ensure drug stability.
1) An emulsion is an unstable mixture of two immiscible liquids, where one liquid is dispersed as globules in the other liquid. Emulsions can be O/W (oil in water) or W/O (water in oil) types.
2) Pharmaceutical emulsions are used to deliver unpleasant tasting drugs, provide slow release of water-soluble drugs, and enhance absorption of oil-soluble drugs.
3) The key steps in formulating an emulsion are selecting an emulsifying agent based on its HLB value, adding preservatives and antioxidants, and using methods like trituration or the bottle method to prepare the emulsion.
The document provides information about short term training conducted at Oniosome Healthcare Pvt. Ltd., including topics covered such as calibration of glassware, determination of melting point and solubility of drugs, determination of hydrophilic-lipophilic balance (HLB) value, thin layer chromatography, high performance liquid chromatography, friability, dissolution, disintegration, and UV spectroscopy. It then discusses the definition of HLB value, how it indicates the polarity of surfactant molecules on a scale of 1-40, and how lipophilic and hydrophilic portions of surfactant molecules affect oil and water solubility. Finally, it outlines methods for determining HLB values and requirements, and applications of surfactants based
1. The document discusses colloidal dispersions, which are systems where particles between 1 nm and 1000 nm are dispersed uniformly throughout a dispersion medium.
2. Colloidal systems are classified based on particle size into molecular dispersions, colloidal dispersions, and coarse dispersions. They are also classified based on particle-medium interactions into lyophilic, lyophobic, and association colloids.
3. The key properties of colloidal systems discussed are electrical properties (surface charge, zeta potential, electrophoresis), optical properties (Tyndall effect, turbidity), and kinetic properties (Brownian motion, diffusion, viscosity).
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
Voltammetry involves applying a time-dependent potential to an electrochemical cell and measuring the resulting current. A voltammogram plots current versus applied potential. Polarography is a type of voltammetry that uses a dropping mercury electrode (DME). With a DME, the potential is measured versus a reference electrode as the mercury drop grows. Current results from redox reactions and is influenced by mass transport and electron transfer kinetics. Non-faradaic currents also occur due to charging of the electrical double layer. A polarogram shows the characteristic diffusion-limited current when sufficient overpotential is applied for an analyte's reduction.
This document outlines objectives and concepts related to colloids and their importance in environmental engineering. It discusses the electrical double layer theory of colloidal surface charge and how colloids can be destabilized through processes like increasing ionic strength or adjusting pH. It also addresses turbidity in water supplies and its environmental significance.
This document discusses colloidal dispersions and their properties. It defines colloidal dispersions as heterogeneous biphasic systems with dispersed particles in the nano size range of 1-1000 nm. Colloids can be classified as lyophilic, lyophobic, or association colloids based on particle-solvent interactions. Key optical properties of colloids include the Tyndall effect, light scattering measurements to determine particle size and molecular weight, and imaging with electron microscopes. Colloids also exhibit kinetic properties like Brownian motion, diffusion, osmotic pressure, and sedimentation rates related to particle size. Electrolytes can cause coagulation or precipitation of colloids according to the Schulze-
Module 1 e (theory of disperse system).pptxDipti Nigam
1) The document discusses key concepts related to disperse systems including particle properties, surface and interfacial phenomena, and instability and stabilization.
2) Particle properties like shape and size distribution impact properties like viscosity, packing stability, and drug delivery. Surface charge and interfacial forces including van der Waals, electrical double layer, and DLVO theory also influence stability.
3) Instability occurs when attractive forces outweigh repulsive forces due to changes in surface energy. Stabilization techniques add electrostatic or steric repulsion to prevent aggregation. The zeta potential and energy barrier height indicate stability according to DLVO theory.
This document discusses plasma and LCD displays. Plasma displays produce glow through electrical discharge in gas, exciting gas atoms which then radiatively decay. AC or DC is used, with typical widths of 100um and 400 torr pressure. Initial firing voltage is 150V, then reduced to 90V. LCD displays are passive, using little power. They have two glass plates filled with liquid crystals, which are rod-like molecules that can align and move relative to surfaces and each other in different phases. Applied electric fields change the alignment of positive liquid crystal materials.
This document provides an overview of Nuclear Magnetic Resonance (NMR) spectroscopy. It discusses key NMR concepts like spin quantum number, instrumentation, solvent requirements, relaxation processes, chemical shift, and coupling constants. The presentation was given by Suraj N. Wanjari and covered topics such as NMR principles, instrumentation, factors affecting chemical shift, and applications of 1H NMR and 13C NMR spectroscopy. References on NMR spectroscopy from several analytical chemistry textbooks are also listed.
SDS-PAGE electrophoresis is a technique used to separate proteins by size. It involves running proteins through a stacking gel and resolving gel with an electric current. The stacking gel concentrates the proteins into a narrow band before entering the resolving gel, which separates the proteins based on size differences. Key components of SDS-PAGE include SDS to impart identical charge-to-mass ratios to proteins, reducing agents to unfold proteins, and polyacrylamide gels which sieve proteins during electrophoresis based on their size.
This document provides an overview of zeta potential, including:
- Zeta potential is the electric potential at the boundary between the double layer and bulk solution surrounding charged particles suspended in a colloidal system.
- Factors that affect zeta potential include pH, thickness of the double layer, and concentration of formulation components.
- Zeta potential is important for predicting particle interactions and stability in colloidal systems based on DLVO theory of electrostatic repulsion and van der Waals attraction.
- Measurement techniques include electrophoresis and electroacoustic methods to determine particle mobility from which zeta potential is calculated.
This document provides an overview of zeta potential, including:
- Zeta potential is the electric potential at the boundary between the double layer and bulk solution surrounding charged particles suspended in a colloid.
- Factors that affect zeta potential include pH, thickness of the double layer, and concentration of formulation components.
- Zeta potential is important for predicting particle interactions and stability in colloidal systems based on DLVO theory of electrostatic repulsion and van der Waals attraction.
- Measurement techniques include electrophoresis and electroacoustic methods to determine particle mobility from which zeta potential is calculated.
This document provides an overview of the electrical double layer (EDL) theory. It describes the three main models of the EDL structure: Helmholtz model (single layer of ions), Gouy-Chapman model (diffuse ion layer), and Gouy-Chapman-Stern model (combination of compact and diffuse layers). The Gouy-Chapman-Stern model is now widely accepted. It depicts the EDL as consisting of an inner Stern layer and an outer diffuse layer. Applications of EDL theory include measuring zeta potential to determine colloid stability and developing the DLVO theory of colloid interactions and stability.
The document discusses electric fields and electric dipoles. It defines the electric field as a vector field generated by electric charges that acts upon other charges. Electric field lines are introduced to visualize electric fields, with higher density of lines indicating stronger fields. Dipoles, such as water molecules, have a built-in electric polarity due to unequal charge distribution. When placed in an external electric field, dipoles experience a torque attempting to align them with the field but do not experience a net force. Microwave ovens work by using an oscillating electric field to cause the rotation of polar water molecules in food, generating heat through molecular collisions.
Electrophoresis is a scientific laboratory technique that is used to separate DNA, RNA, or protein molecules based on their size and electrical charge. An electric current is passed through the molecules to move them so that they can be separated via a gel. The pores present in the gel work like a sieve, allowing smaller molecules to pass through more quickly and easily than the larger molecules. According to the way conditions are adjusted during electrophoresis, the molecules can be separated in the desired size range.
What is electrophoresis and what are its uses?
Electrophoresis is a very broadly used technique that, fundamentally, applies electric current to biological molecules – they’re usually DNA, but they can be protein or RNA, too – and separates these fragments into pieces that are larger or smaller in size.
The phenomenon of electrophoresis was first observed by Russian professors Peter Ivanovich Strakhov and Ferdinand Frederic Reuss in 1807 at Moscow University. A constant application of electric field caused the particles of clay dispersed in water to migrate, showing an electrokinetic phenomenon.
Electrophoresis can be defined as an electrokinetic process that separates charged particles in a fluid using an electrical field of charge. Electrophoresis of cations or positively charged ions is sometimes referred to as cataphoresis (or cataphoretic electrophoresis). In contrast, sometimes, the electrophoresis of anions or negatively charged ions is referred to as anaphoresis (or anaphoric electrophoresis).
It’s used in a variety of applications. Though it is most often used in life sciences to separate protein molecules or DNA, it can be achieved through several different techniques and methods depending upon the type and size of the molecules.
The methods differ in some ways, but all we need is a source for the electrical charge, a support medium and a buffer solution. Electrophoresis is also used in laboratories for the separation of molecules based on their size, density and purity.
The method used to separate macromolecules such as DNA, RNA, or protein molecules is known as gel electrophoresis.
It is used in forensics for –
Nucleic acid molecule sizing
DNA fragmentation for southern blotting
RNA fragmentation for northern blotting
Protein fragmentation for western blotting
Separation of PCR products analysis
Detection and analysis of variations or mutations in the sequence
Its clinical applications involve –
Serum protein electrophoresis
Lipoprotein analysis
Diagnosis of haemoglobinopathies and hemoglobin A1c.
The fundamental principle of electrophoresis is the existence of charge separation between the surface of a particle and the fluid immediately surrounding it. An applied electric field acts on the resulting charge density, causing the particle to migrate and the fluid around the particle to flow.
It is the process of separation or purification of protein molecules, DNA, or RNA that differ in charge, size.
Module 1 e (theory of disperse system).pptxDipti Nigam
The document discusses key concepts related to disperse systems, including:
- Particle properties like shape and size distribution impact properties like viscosity, packing, and stability.
- Surface charge and interfacial phenomena like van der Waals forces, electrical double layers, and zeta potential determine whether attractive or repulsive forces dominate between particles.
- The DLVO theory describes how the total interaction potential (VT) is determined by a balance of attractive van der Waals forces (VA) and repulsive electrostatic forces (VR), with stability requiring the maximum repulsion (Vmax) to exceed ~50 mV.
- Systems can be stabilized against instability through electrostatic or steric repulsion between particles.
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2. ❑ Dispersed systems are systems which consist of:
1. Particulate matter (dispersed phase)
➢ It is the component present in small proportion
and is just like a solute in a solution
2. Dispersion medium (continuous phase)
➢ A component present in excess and is just like a
solvent in a solution
Dispersed
phase
Dispersion
medium
2
Dispersed system
26-Jan-23 a4kgetmes
3. 26-Jan-23 3
Dispersed system
➢Based on particle size: dispersed systems are classified as
Molecular dispersion, Colloidal dispersion and Coarse dispersion
< 1 nm 1 - 500 nm > 500 nm
Property
Particle size
Diffusion
Visibility
Filtration
Settling
Molecular Colloidal Course
Particles diffuse
rapidly
Very slow diffusion Don’t diffuse
Invisible under
electromicroscop
e
Visible under
electromicroscope
Visible under
lightmicroscope
Pass SPM and
filter paper
Pass filter paper
but not SPM
Not pass filter
paper or SPM
Do not settle Settle under
centrifugation
Settle under
gravity
a4kgetmes
4. 26-Jan-23 4
Types of Colloidal Systems
➢ Based on the interaction b/n the two phases colloids are
classified as:
✓Lyophilic colloids: contains particles which interacts with the
dispersion medium to an appreciable extent
✓Example Acacia or gelation in water
✓Lyophobic colloids: composed of materials having poor/no
interaction with the dispersion medium
✓Generally inorganic particles such as gold and silver
✓Association colloids: composed of materials having
amphiphilic nature which could result in to micelles
✓The concentration ---> CMC
✓The no of monomers ---> Aggregation number
a4kgetmes
5. 26-Jan-23 5
Lyophilic
(solvent-loving)
Lyophobic
(solvent-hating).
Association (amphophilic).
Dispersed
phase
Large organic molecules
lying within colloidal size
Inorganic particles such as
gold and silver
Micelles of small organic
molecules (size < colloidal size)
Solvation Solvated Little solvation Depends on the medium
(Hydrophilic/lipophilic)
Preparatio
n
Spontaneous (dissolving
in solvent
Needs special procedure Spontaneous (conc. > CMC)
Viscosity Increases with conc. & at
certain conc. Form a gel.
Not greatly increased due
to no solvation
Increased with conc./micell no.
Effect of
electrolyte
s
Stable but de-solvation &
salting out at high conc.
Unstable due to surface
charges neutralization
CMC is reduced and salting out
occur at high salt conc.
Types of Colloidal Systems
a4kgetmes
6. 26-Jan-23 6
Optical Properties of Colloids
a4kgetmes
Faraday-Tyndall effect and Light scattering
➢ When a strong beam of light is passed through colloidal
dispersions, the light rays form a visible cone (Tyndall cone)
resulting from the light scattered by colloidal particles.
✓ This is called the Faraday-Tyndall effect
➢ This cone formation (Tyndall cone) and Turbidity define the
optical appearance of colloidal dispersions.
7. 7
Optical Properties of Colloids
➢ Turbidity is a fractional decrease in the intensity of an incident
light due to scattering as it passes through a medium.
➢ This light scattering provides information on the particle size,
shape and molecular weight of colloids.
✓ For instance, molecular weight is directly related to turbidity
26-Jan-23
Where τ (cm-1) is turbidity = Is/I
C (g/cm3) is concentration
M (g/mole) is average molecular weight
B is an interaction constant
H is constant for particular system
Hc/τ = 1/M + 2Bc
a4kgetmes
➢ A plot of HC/τ Vs C provides a
straight line with
✓ A slope of 2B and
✓ Y-intercept of 1/M
8. 8
a4kgetmes
kinetic Properties of Colloids
26-Jan-23
➢Brownian motion
✓ It is a random/erratic and continuous movement of colloidal
particles within a dispersion medium.
✓ It results from uneven distribution of collision on the
particles from the molecules of the dispersion medium
✓ This motion is affected by different factors including
✓ Temperature: generally enhances Brownian motion
✓ Particles size: smaller particles move faster
✓ Viscosity: high viscosity limits Brownian motion.
9. 26-Jan-23 9
✓ As a consequence of Brownian motion in a stable colloidal
system:
• The gravitational force (sedimentation) is counteracted
• Colloidal particles diffuse from high to low concentration
kinetic Properties of Colloids
➢Diffusion
✓ It is a spontaneous movement of particles from a higher to
a lower concentration until a system is uniform throughout.
✓ Fick’s first law states “The amount of substance diffusing in
time (dm/dt) across an area (A) is directly proportional to a
change of conc. with distance traveled (dc/dx)”
a4kgetmes
10. 26-Jan-23 10
kinetic Properties of Colloids
➢Osmotic pressure
✓ It is the driving force in osmosis as is the concentration
gradient for diffusion.
✓ The osmotic pressure of a dilute colloidal dispersion can be
described by van’t Hoff’s equation
a4kgetmes
11. 26-Jan-23 11
Sedimentation
Stoke’s law: For spherical particles
V: rate of sedimentation
r: radius of the particle
d: particle diameter
ρ: density of the particle
ρo: density of the medium
η: viscosity of the medium
g: acceleration due to gravity
Limitations of the Stock’s law
➢ It was derived for dilute dispersions and does not take into
consideration inter-particulate interactions.
➢ Thus, it may not be exactly applicable to a concentrated
dispersion system.
a4kgetmes
12. 26-Jan-23 12
Electric Properties of Colloids
➢Electrical properties of colloids are those properties which
depend on, or are affected by, the presence of a charge on the
surface of a particle.
✓Physical stability of colloids
➢ Why particles in a liquid acquire charge?
✓Ion dissolution.
✓Ionization.
✓Ion adsorption (Selective adsorption of a particular ionic
species present in the solution).
a4kgetmes
13. Ion dissolution
❑ Ionic substances can acquire a surface charge by unequal
dissolution of the oppositely charged ions. For instance
➢ Silver iodide particle in a solution with
• Excess iodide, the AgI particles acquire a negative charge
• Excess silver, the AgI particles acquire a positive charge
– Hence, the conc. of Ag and I determine the electric
potential
➢ Similarly, Aluminum hydroxide particles in a solution with
excess hydroxide will acquire a negative charge & vice versa.
26-Jan-23 13
Electric Properties of Colloids
(AgI)m
I- I
-
I
-
a4kgetmes
14. Ionization
❑ Surface charge of colloidal particle is controlled by the
ionization of surface groupings. For instance
➢ Polystyrene latex has carboxylic acid group at the surface,
ionize to give negatively charged particles.
➢ Acidic drugs as ibuprofen & nalidixic acid acquire surface
negative charged.
➢ Amino acids & proteins have carboxyl & amino groups whose
ionization depend on the pH as follow;
NH2-R-COO-
Negatively charged NH3
+-R-COO-
Zwitter ion (neutral)
NH3+-R-COOH
low pH (Acidic medium)
NH2 -R- COOH
14
Electric Properties of Colloids
@ high (Alkaline)pH
@ Isoelectric point
@ low (Acidic) pH
26-Jan-23 a4kgetmes
15. 26-Jan-23 15
Electric Double Layer (EDL)
➢As shown in previous slides, colloidal particles carry electrical
charge on their surface (–ve /+ve) => potential determining ions
➢Consequently, the surface charge attracts counter ions, together
with the dispersion medium, on to the surface of the particles.
✓ Depending on the magnitude and sign (+ve or –ve) of the charge
➢These adsorption proceeds until the surface charge is neutralized
and results in a layer called EDL
➢An EDL is an electrically neutral layer surrounding a dispersed
phase, including adsorbed ions and a film the dispersion medium.
➢An EDL is a phenomenon that plays a fundamental role in the
electrostatic stabilization of colloids.
Electric Properties of Colloids
a4kgetmes
16. 26-Jan-23 16
Electric Properties of Colloids
➢For instance let’s consider an EDL that results from the dispersion
of AgI particles in an aqueous solution of NaI
a4kgetmes
17. 26-Jan-23 17
Electric Properties of Colloids
➢ Nernst potential (E) is the potential at the solid surface aa’, due
to the potential determining ions
➢ The difference in potential between the actual surface and the
electroneutral region of the solution
➢ Zeta potential (ζ) is the potential
located at the shear plane bb’ due to
the contribution of the counter ions.
➢ The potential difference between the
surface of tightly bound layer (shear
plane) and the electroneutral region of
the solution
a4kgetmes
18. 26-Jan-23 18
Electric Properties of Colloids
➢ Zeta potential (ζ) can be determined from one of the
electrokinetic property of colloidal particles- Electrophoresis
➢ Electrophoresis is the mov’t of a charged particle through a liquid
under the influence of applied electric current (potential)
✓ The rate of particle migration is a function of the charge on
the particle (zeta potential)
a4kgetmes
19. 26-Jan-23 19
Electric Properties of Colloids
➢ The magnitude of zeta potential can be determined by
• V= velocity of migration,
• ɛ = dielectric constant,
➢ If the dispersion medium used is water and at 20 oC, the above
equation becomes:
• ɳ = viscosity,
• E = potential gradient (volt/cm)
a4kgetmes
21. 26-Jan-23 21
➢ Important terms to be considered in physical stability of colloids
• Aggregation, Coagulation and Flocculation
Physical stability of colloidal systems
➢ Aggregation
✓ is a general term signifying the
collection of particles into groups.
➢ Flocculation
✓ Is when aggregated particles have
an open structure with a small
distance remain b/n them.
➢ Coagulation
✓ Is when aggregated particles are
closely packed making it difficult
to redisperse them.
a4kgetmes
23. ➢ The physical stability of colloidal dispersions depends on the
balance of involved forces:
✓ Electrical forces of repulsion between dispersed phase
particles (the zeta potential)
✓ Forces of attraction between dispersed phase particles
(including van der Waals force of attraction)
✓ Forces of attraction between the dispersed phase and the
dispersion medium
26-Jan-23 23
Physical stability of colloidal systems
a4kgetmes
24. ❑ Stabilization serves to prevent colloids from aggregation.
N.B:
➢ Hydrophilic and association colloids are thermodynamically
stable
➢ Lyophobic or hydrophobic colloids are thermodynamically
unstable
❑ Two main mechanisms for lyophobic colloid stabilization:
➢ 1-Steric stabilization
• surrounding particles with polymer molecules attached to
its surface forming a coating, which creates a repulsive
force and separates the particle from another particle.
➢ 2-electrostatic stabilization
• providing the particles with electric charge
26-Jan-23 24
Physical stability of colloidal systems
a4kgetmes
25. ❑ Derjaguin and Landau and, independently, Verwey and
Overbeek, in the 1940s produced a quantitative approach to the
stability of hydrophobic colloids.
➢ DLVO theory of colloid stability
❑ They assumed that the only interactive forces
involved are:
➢ van der Waals attraction (VA) and
➢ electrical repulsion, (VR)
❑ And these parameters are additive.
➢ Thus the total potential energy of interaction
VT =VA + VR
26-Jan-23 25
DLVO theory of colloid stability
a4kgetmes
26. ➢ The DLVO theory explains the tendency of dispersed particles to
agglomerate or remain discrete by combining the van der Waals
attraction curve with the electrostatic repulsion curve to form the
net interaction.
26-Jan-23 26
DLVO theory of colloid stability
a4kgetmes
27. • The curve shows that:
• Attraction predominates at small
distances, hence the very deep
primary minimum.
• The attraction at large interparticle
distances that produces the
secondary minimum arises
• Because the fall-off in repulsive
energy with distance is more rapid
than that of attractive energy.
• At small and at large distances the
van der Waals energy is greater than
the repulsion
• At intermediate distances double-
layer repulsion may predominate,
giving a primary maximum in the
curve, particles stay dispersed
26-Jan-23 27
DLVO theory of colloid stability
a4kgetmes
28. ❑ If the maximum is too small, two interacting particles may
reach the primary minimum
➢ Will form aggregation
❑ When the maximum in VT total is sufficiently high, the two
particles do not reach the stage of being in close contact.
➢ Stable colloid will be formed
26-Jan-23 28
DLVO theory of colloid stability
a4kgetmes
29. ❑ Therapeutic purpose
➢ Colloidal system are used as therapeutic agents in different
areas.
Eg. Silver colloid → germicidal
Copper colloid → anticancer
Mercury colloid → Antisyphilis
❑ Stability, solubility
➢ Colloidal coatings to solid dosage forms are used to protect
drugs that are susceptible to atmospheric moisture or
degradation under the acid condition of the stomach.
➢ Association colloids are used to increase solubility &
stability of certain compounds in aqueous & oily
pharmaceutical preparations.
26-Jan-23 29
Application of colloids
a4kgetmes
30. ❑ Absorption
➢ As colloidal dimensions are small enough, they have a huge
surface area.
• Hence, the drug constituted in colloidal form is released in
large amount.
e.g. sulphur colloid gives a large quantity of sulphur
❑ Targeted Drug Delivery
Eg. Liposomes are of colloidal dimensions and are preferentially
taken up by the liver and spleen.
➢ Hence, principle of colloids is also used in targeted drug
delivery system
26-Jan-23 30
Application of colloids
a4kgetmes
32. ❑ A pharmaceutical suspension is a dispersion in which internal
phase (API)is dispersed uniformly throughout the external phase.
❑ The internal phase consisting of insoluble solid particles having a
size range of (0.5 to 5 microns) which is maintained uniformly
through out the suspending vehicle with aid of single or
combination of suspending agent.
❑ The external phase (suspending medium) is generally aqueous in
some instance, may be an organic or oily liquid for non oral use.
Pharmaceutical suspensions
26-Jan-23 32
a4kgetmes
33. Classifications of suspensions
❑ Based on route of administration
➢ Oral suspension eg: Paracetamol suspension, antacids
➢ Externally applied suspension eg : Calamine lotion
➢ Parenteral suspension eg: Penicillin G Benzathine, Insulin Zinc
Suspension
❑ Based on proportion of solid particles
➢ Dilute suspension (2 to10%w/v solid): cortisone acetate
➢ Concentrated suspension (50%w/v solid): zinc oxide
suspension
Suspensions…
26-Jan-23 33
a4kgetmes
34. ❑ Based on Electrokinetic Nature of solid particles
➢ Flocculated suspension
➢ Deflocculated suspension
❑ Based on size of solid particles
➢ Coarse suspensions: Suspensions with suspended particle
sizes of 1 to 100 µm
➢ Colloidal suspensions: Suspensions with suspended particle
sizes of 1 nm to 1 µm.
➢ Nano suspensions: Suspensions with suspended particle sizes
of < 1 nm
Suspensions…
26-Jan-23 34
a4kgetmes
35. ❑ Based on the ease of suspendability the solid particle:
➢ Diffusible suspensions
• Contain light powders (insoluble, or only very slightly
soluble) but after shaking disperse evenly throughout the
vehicle for long enough
❑ Examples of diffusible powders commonly incorporated into
pharmaceutical suspensions
* Light Kaolin BP (insoluble in water)
* Light Magnesium Carbonate BP (very slightly soluble)
* Magnesium Trisilicate BP (insoluble )
Suspensions…
26-Jan-23 35
a4kgetmes
36. ❑ In-diffusible suspensions
➢ contain heavy powders that are insoluble in the vehicle
and on shaking do not disperse evenly throughout the
vehicle long enough
Examples:
* Aspirin BP
* Calamine BP
* Chalk BP
* Zinc Oxide BP
Suspensions…
26-Jan-23 36
a4kgetmes
37. Advantages:
❑ Suspension can improve chemical stability of certain drug.
• Powder for reconstitution
• Drugs prone to hydrolysis: Tetracycline/oil
❑ Drug in suspension exhibits higher rate of bioavailability than
other dosage forms.
• Solution > Suspension > Capsule > Compressed Tablet > Coated tablet
❑ To mask the unpleasant odour/bitter taste of drugs
Eg: paracetamol suspension (more palatable)
❑ Suspension can be used for topical applications
Eg: calamine lotion Bp
❑ Suspension can be formulated for parentral application
E.g. Penicillin G Benzathine
Advantages and Disadvantages
26-Jan-23 37
a4kgetmes
38. Disadvantage
❑ Physical stability, sedimentation and compaction can causes
problems.
❑ It is bulky sufficient care must be taken during handling and
transport.
❑ It is difficult to formulate a stable and acceptable suspension
❑ Uniform and accurate dose can not be achieved unless
suspension are packed in unit dosage form.
Advantages and Disadvantages…
26-Jan-23 38
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39. ❑ Resuspend easily upon shaking
❑ Physically, chemically and microbiologically stable during its
shelf life
❑ Uniform dispersion
❑ Sterile (parenteral, ocular)
❑ Gets into syringe (parenteral, ocular)
❑ Pleasing odor and color and Palatable
❑ Easy to pour yet not watery and no grittiness
❑ Temperature insensitive
Properties of an Ideal Suspension
26-Jan-23 39
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40. ❑ Some FACTORS TO BE CONSIDERED during formulation of
suspensions are:
• PARTICLE SIZE CONTROL
• WETTING
• SEDIMENTATION
• ZETA POTENTIAL
Theoretical consideration of suspensions
26-Jan-23 40
a4kgetmes
41. PARTICLE SIZE CONTROL
❑ Particle size of any suspension is critical and must be reduced
within the range.
• Too large or too small particles should be avoided.
❑ Larger particles will:
• settle faster at the bottom of the container
• particles > 5 μm
– impart a gritty texture to the product
– cause irritation if injected or instilled to the eye
• particles > 25 μm may block the needle
❑ Too fine particles will
• easily form hard cake at the bottom of the container.
Theoretic consideration of suspensions…
26-Jan-23 41
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42. WETTING OF THE PARTICLES
❑ Hydrophilic materials (such as talc and Mg2CO3) are easily wetted
by the dispersion medium commonly water
❑ Conversely, hydrophobic materials (such as sulphur and charcoal)
are not easily wetted b/c a layer of adsorbed air on their surface.
❑ Thus, the particles, even high density, float on the surface of the
liquid until the layer of air is displaced completely.
❑ The use of wetting agent allows removal of this air from the
surface and to easy penetration of the vehicle into the pores.
❑ However, hydrophobic materials are easily wetted by non-polar
dispertion liquids.
Theoretic consideration of suspensions…
26-Jan-23 42
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43. SEDIMENTATION
❑ Sedimentation means settling of particle or floccules occur
under gravitational force in liquid dosage form.
❑ Velocity of sedimentation is expressed by Stoke’s equation
v =
d2 (p1-p2) g
18
v =
d2 (p1-p2) g
18
where v is the terminal velocity in cm/sec.
d is the diameter of the particle in cm,
p1 and p2 are the densities of the dispersed phase and dispersion
medium, respectively.
g is the acceleration due to gravity, and is the viscosity of the
dispersion medium in poise
Theoretic consideration of suspensions…
26-Jan-23 43
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44. ❑ According to Stoke’s Law rate of sedimentation of particles
in a suspension may be reduced by:
➢ decreasing particle size
➢ increasing viscosity
➢ Narrowing density difference of dispersed and
dispersion phase
Theoretic consideration of suspensions…
26-Jan-23 44
a4kgetmes
45. ZETA POTENTIAL
❑ Zeta potential is a measure of repulsive forces.
❑ 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 de flocculation
depends on zeta potential carried by particles.
Theoretic consideration of suspensions…
26-Jan-23 45
a4kgetmes
46. Flocculated Suspensions
❑ In flocculated suspensions, zeta potential is lower than critical
values where attractive forces are greater than repulsive forces
❑ This lower zeta potential leads to the formation of loose
aggregates of particles (flocs) => flocculation
❑ Zeta potential can be lowered by addition of a small amount of
electrolyte or nonionic surfactants to deflocculated suspensions
❑ The formed flocs will cause increase in sedimentation rate due to
increase in size of sedimenting particles.
➢ Hence, flocculated suspensions sediment more rapidly.
❑ However, this formation of flocs and rapid sedimentation allows
the entrapment of dispersion medium
Deflocculation and Flocculation…
26-Jan-23 46
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47. Deflocculated suspensions
❑ In deflocculated suspensions, the zeta potential is higher than
critical value where repulsive forces supersede attractive ones.
❑ Consequently, particles remains suspended for a long period of
time, and only a small portion of the suspended particles are
found in the sediment due to the force of gravitation.
❑ In deflocculated suspension, individual particles are settling with
a slow rate of sedimentation
❑ This prevents the entrapment of the dispersion medium between
settling particles making it difficult to re-disperse by agitation.
❑ This phenomenon is called ‘caking’ or ‘claying’.
Deflocculation and Flocculation
26-Jan-23 47
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48. Flocculated Deflocculated
1. Particles forms loose aggregates and
form a network like structure
2. Rate of sedimentation is high
3. Sediment is rapidly formed
4. Sediment is loosely packed and
doesn’t form a hard cake
5. Sediment is easy to redisperse
6. Suspension is not pleasing in
appearance
7. The floccules stick to the sides of the
bottle
1. Particles exist as separate entities
2. Rate of sedimentation is slow
3. Sediment is slowly formed
4. Sediment is very closely packed
and a hard cake is formed
5. Sediment is difficult to redisperse
6. Suspension is pleasing in
appearance
7. They don’t stick to the sides of the
bottle
Deflocculation and Flocculation…
26-Jan-23 48
a4kgetmes
49. ❑ The formulation of a suspension depends on whether the
suspension is flocculated or deflocculated.
❑ Three approaches are commonly involved
– Use of structured vehicle
– Use of controlled flocculation
– Combination of both of the methods
Formation of suspensions
26-Jan-23 49
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50. Flow chart of formulation of suspension
Finely divided Particles
Addition of
structured vehicle
Addition of wetting agent and dispersion medium
Deflocculated suspension
in structured vehicle as a
final product
Flocculated
suspension
Flocculated
suspension as a final
product
Uniform dispersion of deflocculated particles
Addition of
flocculating agent
Addition of
flocculating agent
Addition of
structured vehicle
Flocculated suspension in
structured vehicle as a final
product
26-Jan-23 50
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51. STRUCTURED VEHICLE
❑ Structured vehicles are aqueous solutions of natural gums and
synthetic (modified) polymers.
❑ Structured vehicles are also known as thickening or suspending
agents.
❑ The main aim of these agents is to increase the viscosity of the
suspension, or specifically the dispersion medium.
❑ These structured vehicles entrap the particles and reduce their
sedimentation.
❑ E.g. methyl cellulose, sodium carboxy methyl cellulose, acacia,
gelatin and tragacanth.
Formation of suspensions…
26-Jan-23 51
a4kgetmes
52. CONTROLLED FLOCCULATION
❑ Controlled flocculation of particles is obtained by adding
flocculating agents, which are:
– Electrolytes
– Surfactants
– Polymers
FLOCCULATION IN STRUCTURED VEHICLES
❑ Sometimes suspending agents can be added to flocculated
suspension to retard sedimentation
❑ Examples of these agents are: Carboxymethylcellulose (CMC)
Formation of suspensions…
26-Jan-23 52
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53. ❑ Suspending agent: form colloidal dispersion with Water and
increase the viscosity of the continuous phase.
➢ Preferred suspending agents are those that give thixotropy to the
media such as Xanthan gum, Carageenan, Na CMC.
❑ Wetting agent: increase wettability: Alcohol, glycerin, and propylene
glycol, polysorbate 80
❑ Buffers: control the pH: acetate, phosphate citrate, carbonate
❑ Osmotic agents: added to produce osmotic pressure comparable to
biological fluids: NaCl, manitol, dextros
Formation ingredients used in suspensions
26-Jan-23 53
a4kgetmes
55. ❑ Small scale preparation of suspensions:
Step 1: The insoluble materials are ground (levigated) in a mortar
with the vehicle and wetting agent in to a smooth paste.
Step 2: All soluble ingredients are then dissolved in same portion of
the vehicle and added to the smooth paste to get a slurry.
Step 3: The slurry is transferred to a graduated cylinder, the mortar
is rinsed with successive portion of the vehicle.
Step 4: Add a vehicle containing the suspending agent/ flocculating
agent and then make up the dispersion to the final volume
Preparation of suspensions
26-Jan-23 55
a4kgetmes
56. Sedimentation method :
❑ Two parameters are studied for determination of sedimentation.
1. Sedimentation volume
2. Degree of flocculation
Evaluation of suspensions
26-Jan-23 56
a4kgetmes
57. 1. Sedimentation volume
❑ The ratio of the equilibrium volume of the sediment (Vu) to the
total volume of the suspension (Vo)
F = Vu / Vo = Hu/Ho
❑ F has values ranging from less than one to greater than one.
➢ When Vu < Vo F < 1
➢ When Vu = Vo F =1, flocculation equilibruim, shows no clear
supernatant on standing
➢ When Vu > Vo, F > 1, the network of flocs formed is so loose
(fluffy) that their volume is greater than the original volume.
❑ However, sedimentation volume lacks a meaningful reference
point it gives only qualitative account of flocculation
Evaluation of suspensions…
26-Jan-23 57
a4kgetmes
59. 2. Degree of flocculation (β)
❑ In a suspension that is completely deflocculated, the ultimate
volume of sediment will be relatively smaller than that of
flocculated suspension.
F∞=V∞ /Vo, F=Vu/Vo
❑ Degree of flocculation is the ratio of the sedimentation volume of
the flocculated suspension, F, to the sedimentation volume of the
deflocculated suspension, F∞
ß = F / F∞=[Vu/Vo]/[V ∞ /Vo]= Vu/V∞
❑ The minimum value of ß is 1,when flocculated suspension
sedimentation volume is equal to the sedimentation volume of
deflocculated suspension.
Evaluation of suspensions…
26-Jan-23 59
a4kgetmes
60. 60
Example 1:
Determine the sedimentation volume of a 2.5% w/v suspension of
paracetamol in water. The initial volume of the suspension was 100 mL
while the final volume of the sediment was found to be 44 mL. If the
degree of flocculation is 1.5, what is the deflocculated sedimentation
volume?
Example 2:
A 200 mL of suspension of a drug in water was made and the final volume
of the sediment was found to be 60 mL. Calculate the sedimentation
volume and deflocculated sedimentation volume if the degree of
flocculation is found to be 1.3.
Eg.3. Calculate the sedimentation volume and the deflocculated
sedimentation volume of 5%w/v suspension of magnesium carbonate in
water if initial volume is 100ml, final volume is 30ml and degree of
flocculation is 1.3
26-Jan-23 a4kgetmes
61. ❑ Pharmaceutical suspensions for oral use are generally packed in
wide mouth container having adequate space above the liquid to
ensure proper mixing.
❑ Generally glass and various grades of plastics are used in
packaging of suspension
❑ Parenteral suspensions are packed in either glass ampoules or
vials.
Packaging of suspensions
26-Jan-23 61
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62. Labeling:
❑ Shake well before use
❑ Do not freeze
❑ Protect from direct light (for light sensitive drugs)
❑ In case of dry suspensions powder the specified amount of
vehicle to be mixed may indicated clearly on label.
Storage:
❑ Stored at controlled temperature from 20-25 0C
❑ Suspensions should be stored in cool place but should not be
kept in a refrigerator
Storage requirements & labeling
26-Jan-23 62
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64. ❑ An emulsion is a system consisting of two immiscible liquid
phases, one of which is dispersed throughout the other in the
form of fine droplets.
❑ Heterogeneous systems of one liquid dispersed throughout
another in the form of droplets
Compositions
❑ Internal/Discontinuous/Dispersed phase
➢ The phase that is present as fine droplets
❑ External/Continuous phase
➢ The phase in which the droplets are dispersed
❑ Emulsifying agent
➢ Used to stabilize the emulsion
26-Jan-23 64
Emulsions…
a4kgetmes
65. ❑ Pharmaceutical emulsions usually consist of water and an oil.
➢ depending upon whether the continuous phase is aqueous or
oily, two main types can exist:
A) Oil-in-water (o/w)
B) Water-in-oil (w/o)
65
26-Jan-23
Emulsions…
a4kgetmes
66. ❑ For oral administration, o/w emulsions are used while for
external use, both o/w and w/o systems can be employed.
❑ Semisolid emulsions are termed as creams
➢ O/w creams are less greasy and are easily washable after
application.
➢ W/o creams are greasy, with high apparent viscosity
• have an occlusive effect and are therefore preferred as
moisturizing lotions.
26-Jan-23 66
Emulsions…
a4kgetmes
67. ❑ O/W emulsions are administered by all the major parenteral
routes
❑ W/o emulsions are generally reserved for IM or SC
administration where sustained release is required
➢ Drug action is prolonged in such oily emulsions because the
drug has to diffuse from the aqueous dispersed phase
through the oil-continuous environment to reach the tissue
fluids
➢ Besides, w/o emulsion is generally of high viscosity: difficult
to inject
26-Jan-23 67
Emulsions…
a4kgetmes
68. Multiple emulsions
❑ Are emulsions whose disperse phase contains droplets of another
phase
➢ An oil droplet enclosing a water droplet may be suspended in
water to form a water-in-oil-in water emulsion (w/o/w)
• Use: as delayed-action drug delivery systems
• lower the viscosity of w/o emulsion
26-Jan-23 68
Emulsions…
a4kgetmes
69. ❑ When two immiscible liquids are mixed, shaken together or
mechanically agitated both phases tend to form droplets of
various sizes.
❑ The surface free energy of the system, which is dependent on
both total surface area and interfacial tension is raised by the
increase in surface area produced during dispersion,
➢ Thus the system becomes thermodynamically unstable, which
results in coalescence of these droplets
❑ If agitation ceases, coalescence will continue until complete
phase separation, the state of minimum free energy, is reached
26-Jan-23 69
Emulsions formation
a4kgetmes
70. ❑ To prevent coalescence of emulsion, emulsifying agents are
included
❑ Emulsifiers can be grouped into three groups:
1) surface active agents
2) natural (macromolecular) polymers and
3) finely divided solids.
26-Jan-23 70
Emulsions formation…
a4kgetmes
71. ✓ Surfactants adsorption at the oil-water interface form
monomolecular films
• Presence of the surfactant monolayer at the surface of
the droplet reduces the possibility of collisions
– helps to maintain the particles in a dispersed state
❑ The choice of surfactant depends on its solubility to the
phases
❑ In general, the phase in which the emulsifier is most soluble
becomes the continuous phase
• Hydrophilic surfactants→ o/w emulsions (HLB:9-12)
• Lipophilic surfactants promote w/o emulsions (HLB:3-6)
26-Jan-23 71
Emulsions formation…
a4kgetmes
72. ✓ Natural (macromolecular) polymers
▪ Multimolecular Adsorption and Film Formation
➢ Hydrated lyophilic colloids can be regarded as surface
active, but they differ from synthetic surfactant
❖ They do not cause an appreciable lowering of
interfacial tension
❖ They form a multi-rather than a monomolecular film
at the interface
26-Jan-23 72
Emulsions formation…
a4kgetmes
73. ✓ Solid-Particle adsorption
➢ Finely powdered solid particles are wetted to some
degree by both oil and water can act as emulsifying agents
➢ Powders that are wetted preferentially by water form o/w
whereas those more easily wetted by oil form w/o
emulsions
26-Jan-23 73
Emulsions formation…
a4kgetmes
74. 26-Jan-23 74
Table. Emulsifying agents derived from natural products and finely divided solids
Emulsions formation…
a4kgetmes
75. Other ingredients used in emulsions
❑ Antioxidants: butylated hydroxy toulene (BHT) and butylated
hydroxyanisole (BHA)
❑ Humectants: propylene glycol, glycerol, and sorbitol are often
added to dermatological preparations
❑ Preservatives: benzoic acid, parahydroxybenzoic acid esters,
phenoxyethanol, Chloroform Water
➢ W/o emulsions are less susceptible to attack than o/w
emulsions because the aqueous continuous external phase
can produce ideal conditions for the growth of bacteria,
moulds and fungi.
26-Jan-23 75
Emulsions formation…
a4kgetmes
76. ❑ Bacteria can degrade nonionic and anionic emulsifying agents,
Glycerin, Vegetable gums (as thickeners);
➢ Resulting in: Phase separation, Gas and odor formation,
discoloration , Changes in rheological properties
❑ Two phase system: adequate concentration of preservative should be
available in water phase as bacteria mainly grow in aqueous phase
• Therefore, Preservative should
– strongly partitioned in favor of water
– be in its un-ionized form to penetrate bacterial membrane
– not be bound to other components of the emulsion
76
26-Jan-23
Preservation of Emulsions
a4kgetmes
77. ❑ Emulsion may be prepared in different methods
❑ In small scale
➢ a mortar and pestle, a mechanical blender, a homogenizer.
❑ In large scale,
➢ Colloid mills, high-pressure homogenizers, microfluidizers,
ultrasonic homogenizers may be used to prepare an
emulsion.
❑ In small scale, there are three main methods of Emulsion
Preparation
1. Continental or dry gum method.
2. English or wet gum method.
3. Bottle method.
a4kgetmes 77
Methods of Emulsion preparation
26-Jan-23
78. ❑ Also referred to as the 4-2-1 method
• Oil -4 parts by volume
• Aqueous phase -2 parts by volume
• Gum -1 part by weight
❑ The preparation of an emulsion has two main components:
➢ Preparation of a concentrate called the ‘primary emulsion’.
➢ Dilution of the concentrate.
❑ The proportions are important when making the primary
emulsion, to prevent the emulsion breaking down on dilution
or storage.
a4kgetmes 78
Dry gum method
26-Jan-23
79. ❑ Example 1. What quantities would be required to produce 200
mL of 30% v/v Cod liver oil emulsion?
➢ 60mL of Cod Liver Oil BP is required, therefore 4 parts
60mL.
➢ Two parts would be equivalent to 30 ml aqueous phase.
➢ 1 part would be equivalent to 15 g of gum
26-Jan-23 79
Dry gum method
a4kgetmes
80. 1. The acacia or O/W emulsifier is triturated with the oil in a
dry mortar, until uniformly mixed.
2. The two parts of water are added all at once.
➢ Then the mixture is triturated immediately, rapidly and
continuously until the primary emulsion is formed.
• (The end point of the preparation could be noticed
when a creamy white and crackling sound or ‘clicking’
sound is observed).
a4kgetmes 80
Dry gum method, steps
26-Jan-23
81. 3. Other liquid ingredients that are soluble in the external phase
may then be added.
4. Solid substances such as active ingredient, preservatives,
colorants, and flavoring agent usually dissolved in water then
added to an emulsion.
5. Any substance which might reduce the physical stability of the
emulsion, such as alcohol (which may precipitate the gum)
should be added as near to the end of the process as possible
to avoid breaking the emulsion
6. Finally QS with water to final volume
a4kgetmes 81
Dry gum method, steps
26-Jan-23
82. ❑ The same proportion of water, gum and oil is used but the
process is different
❑ More difficult to use, but produces a more stable product
❑ Produces O/W emulsion
Steps:
1. Triturating of acacia with water in a mortar.
2. The oil is added slowly in portions, triturating continuously.
3. The mixture is triturated for several minutes to form the
primary emulsion.
4. Additional water can be added after the primary emulsion is
prepared
5. Other substances may be added.
6. Finally QS with water to final volume
a4kgetmes 82
Wet gum method
26-Jan-23
83. ❑ Another variant of the Continental Method
❑ It is used for volatile oils or oleaginous substances of low
viscosity.
1. The powder acacia is placed in a dry bottle.
2. Two parts of oil then added.
3. The bottle is then capped and shaken.
4. Water is then added immediately in portions.
5. Shaken until primary emulsion is formed
6. Additional water can be added after the primary emulsion is
prepared
5. The other ingredients are added.
6. Finally QS with water to final volume
a4kgetmes 83
Bottle method
26-Jan-23
84. ❑ Dilution test
❑ Dye solubility test
❑ Conductivity test
26-Jan-23 84
Tests for identification Emulsion type
a4kgetmes
85. ❑ A stable emulsion may be defined as a system in which
the
• Globules retain their initial character
• Remain uniformly distributed throughout the continuous
phase.
26-Jan-23 85
Physical stability of emulsion
• Different instability problems
• Reversible: such as creaming and flocculation
• irreversible: such as coalescence and Ostwald ripening
a4kgetmes
87. CREAMING and SEDIMENTATION
❑ The disperse phase, according to its density relative to that of the
continuous phase, rises to the top or sinks to the bottom of the
emulsion, forming a layer of more concentrated emulsion.
➢ If the dispersed phase is less dense than the continuous phase
(o/w emulsion), the velocity of the sedimentation becomes
negative, an upward creaming
➢ If the dispersed phase is more dense than the continuous
phase (w/o emulsion), the velocity of the sedimentation
becomes positive, downward creaming
87
26-Jan-23
Physical stability…
a4kgetmes
88. 88
➢ The rate of creaming can be increased
✓ If the density difference is greater
✓ By increasing the force of gravity through centrifugation
✓ By increasing the diameter of the globule
❑ Creaming is undesirable from a pharmaceutical point of view:
➢ Creamed emulsion is inelegant in appearance,
➢ Possibility of inaccurate dosage,
➢ Increases the likelihood of coalescence as the globules are
close together in the cream.
26-Jan-23
Physical stability…
a4kgetmes
89. ❑ Rate of sedimentation will be decreased by:
➢ reduction in the globule size (eg by homogenizing the
emulsion)
➢ increasing viscosity of continuous phase (eg. by the use of
thickening agents such as tragacanth or methyl cellulose)
➢ decrease in the density difference between the two phases
89
26-Jan-23
Physical stability…
a4kgetmes
90. FLOCCULATION
❑ A weak reversible association between emulsion globules
separated by thin films of continuous phase.
➢ The individual droplets retain their separate identities, but
each floccule or cluster of droplets behaves physically as a
single unit.
➢ The association arises from the interaction of attractive and
repulsive forces between droplets
90
26-Jan-23
Physical stability…
a4kgetmes
91. COALESCENCE
❑ Where dispersed phase droplets merge to form larger droplets
❑ Factors:
• Relative magnitude of forces between droplets
• Disruption of interface
• Dehydration, freezing
❑ Strategies to reduce coalescence
➢ Adding thickening or gelling agent
➢ Increase thickness of interface
➢ Increase repulsion or reduce Attraction
91
26-Jan-23
Physical stability…
a4kgetmes
92. CRACKING or BREAKING
❑ Separation of an emulsion into its constituent phases
➢ the disperse phase coalesces and forms a separate layer.
➢ Re-dispersion cannot be achieved by shaking and the preparation
is no longer an emulsion.
❑ Cracking can occur if the oil turns rancid during storage
➢ Addition of a chemical that is incompatible with the
emulsifying agent, thus destroying its emulsifying ability.
Eg. Surface active agents of opposite ionic charge, (e.g. the
addition of cetrimide (cationic) to an emulsion stabilized
with sodium oleate (anionic))
92
26-Jan-23
Physical stability…
a4kgetmes
93. ❑ Bacterial growth: protein materials and non-ionic surface-active
agents are excellent media for bacterial growth;
❑ Temperature change:
➢ rise in temperature: protein emulsifying agents may be
denatured and the solubility characteristics of non-ionic
emulsifying agents change
➢ Freezing: ice formed disrupt the interfacial film around the
droplets
93
26-Jan-23
Physical stability…
a4kgetmes
94. PHASE INVERSION
❑ This refers to the process whereby there will be an exchange
between the disperse phase and the dispersion medium.
• For example, an O/W emulsion may with time or change of
conditions invert to a W/O emulsion
Causes
➢ Coalescence: results in the formation of progressively larger
droplet which leads to phase separation
➢ Factors that affect the HLB of the system,
Eg. , temperature and/or electrolyte concentration
94
26-Jan-23
Physical stability…
a4kgetmes
95. ❑ Volume fraction of the disperse phase
➢ For stability of an emulsion, the optimum range of
concentration of dispersed phase is 30–60% of the total volume.
➢ If the disperse phase exceeds this the stability of the emulsion is
questionable.
➢ As the concentration of the disperse phase approaches a
theoretical maximum of 74% of the total volume, phase
inversion is more likely to occur.
❑ Addition of electrolyte
➢ Addition of CaCl2 in to o/w emulsion formed by sodium stearate
can be inverted to w/o emulsion
95
26-Jan-23
Physical stability…
a4kgetmes