The document discusses particle size analysis in pharmacy. It defines micromeritics as the science of small particles measured in micrometers. Particle size impacts properties like release, absorption, stability and dosage uniformity. Various methods to determine particle size are described including optical microscopy for sizes 0.2-100 μm, sieving for 40-9500 μm, sedimentation for 0.08-300 μm, and conductivity methods for 0.5-300 μm. Factors like distribution, averages, and diameters are also covered.
KOTA COLLEGE OF PHARMACY discusses atropisomerism in biphenyl compounds, which are stereoisomers where rotation is hindered about a single bond, resulting in isomers with differing stability due to steric strain or a rotational barrier, allowing the isomers to be isolated individually.
Micromeritics involves the study of small particles between 1-100 microns in size. It characterizes particles based on their size, shape, surface area, density, and other properties. Particle size is important for drug release, absorption, stability of formulations, and ensuring uniform drug doses. Methods to determine particle size include optical microscopy, sieving, sedimentation, and conductivity. No single method can directly measure all particle dimensions, so results may vary between methods depending on the intended application.
This document discusses micromeritics, which is the science of small particles. It describes particle size and distributions, and methods to determine particle size such as microscopy, sieving, and sedimentation. It also addresses density and flow properties of powders, which are important for manufacturing tablets and capsules. Control of particle size is essential for drug release, absorption, stability of formulations, and dose uniformity.
This document discusses various methods for measuring rheological properties such as viscosity and thixotropy. It describes key characteristics of thixotropic systems like hysteresis and how instruments can determine structural breakdown. Common viscometers are described including capillary, falling sphere, and bob-cup designs. The bob-cup viscometer uses concentric cylinders and can measure properties like plastic viscosity and yield value. Thixotropic formulations are desirable in pharmaceuticals as they remain thick in containers but spread easily upon administration. Degree of thixotropy impacts sedimentation rate and can enable drug depots to form after intramuscular injection.
Coarse dispersions are heterogeneous systems where the dispersed particles are larger than 1000 nm. They are characterized by relatively fast sedimentation. The dispersed phase may be easily separated from the continuous phase by filtration. A pharmaceutical suspension is a coarse dispersion where the internal phase is uniformly dispersed throughout the external phase. The internal phase typically has particle sizes between 0.5-5 microns. Suspensions demonstrate properties like pseudoplasticity and thixotropy which influence stability during manufacture and storage.
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-
This document provides information about sympathomimetic agents. It discusses direct-acting, indirect-acting, and mixed-acting agents and how they work. Specific agents are described, including their properties, mechanisms of action, uses, and storage requirements. Sympathomimetic drugs act on adrenergic receptors to increase heart rate and blood pressure. Structure-activity relationships are also covered, explaining how chemical modifications impact receptor selectivity and duration of action.
The document discusses chiral molecules and their reactions. Chiral molecules have non-superimposable mirror images due to having four different groups attached to a carbon atom without symmetry. There are three major reactions for chiral molecules: retention, where the configuration of substrate and product remain the same; inversion, where the isomer converts to the other form through an SN2 mechanism; and racemization, where a second chiral center forms diastereomers.
The document discusses micromeritics, which involves characterizing individual particles and particle size distributions in powders. Key properties used to characterize particles include size, shape, volume, surface area, and density. Common methods to determine these properties include optical microscopy, sieving, sedimentation, and conductivity/Coulter counter methods. Particle size distribution and factors that influence powder properties like flow and density are also examined.
This document discusses different types of deformation of solids including plastic deformation, elastic deformation, and the Heckle equation. It defines stress as force per unit area and strain as the measure of deformation. The key types of stress are direct, indirect, and combined, while the main types of strain are tensile, compressive, and shear. Elastic modulus determines the amount of force required for deformation. The Heckle equation models the densification of powders under compression and can be used to determine the yield pressure of particles from the slope of the linear region of the Heckle plot.
1. Complex compounds are molecules where some bonds cannot be described by classical theories of valency and involve anomalous bonds.
2. Complexes form through interactions like coordination bonds, hydrogen bonds, and van der Waals forces between different chemical species.
3. Complexation can alter properties like solubility, conductivity, and chemical reactivity and is used in applications like increasing drug solubility, purification of water, drug analysis, and as anticoagulants.
This document discusses different methods for purifying colloidal dispersions, including dialysis, electrodialysis, and ultrafiltration. Dialysis involves diffusing low molecular weight impurities out of a colloidal solution through a semi-permeable membrane. Electrodialysis enhances this diffusion process by applying an electric potential. Ultrafiltration uses an ultrafilter membrane with small pores to retain colloidal particles while filtering out smaller solutes under pressure.
This document summarizes the structure-activity relationships of phenothiazine drugs. It notes that substitution at the 2-position and N-10 position is important for activity. The best substituents are electron-withdrawing groups at the 2-position, which increase antipsychotic effects. A three-carbon chain between the 10-position and amine nitrogen is critical for neuroleptic activity. The amine must be tertiary. Phenothiazines are thought to act as antagonists at dopamine receptors in the limbic system to treat thought disorders like schizophrenia.
PARASYMPATHOMIMETIC DRUGS Classification and SAR.pptxJasmine Chaudhary
This document discusses parasympathomimetic drugs, also known as cholinergic drugs, which mimic the action of acetylcholine in the body. It describes two types of cholinergic drugs: direct-acting drugs that stimulate cholinergic receptors, and indirect-acting drugs that inhibit the acetylcholinesterase enzyme and increase acetylcholine levels. The document provides details on the classification, structure-activity relationships, mechanisms of action, effects, and examples of both types of cholinergic drugs.
This document summarizes information about two adrenergic drugs. Phenylephrine is used for temporary relief of stuffy nose, sinus, and ear symptoms caused by common colds, flu, allergies, or other breathing illnesses by decreasing swelling in the nose and ears. Salbutamol relaxes the smooth muscle in the lungs and opens airways to improve breathing and is used to treat asthma, chronic bronchitis, emphysema, and prevent exercise-related asthma. The document was written by Dr. P Parthiban, a professor at Vellalar College of Pharmacy.
R. VIJAYAKUMAR., M Pharm,
Research Scholar
department of Pharmaceutical Technology.
Anna university- BIT
Tiruchirappalli
III Semester.
UNIT-IV / Micromeritics
This document provides information about micromeritics, which is the science and technology of small particles. It discusses several key concepts in micromeritics including particle size, shape, density, and surface area. The document then describes several important applications of micromeritics in the pharmaceutical field related to drug release, absorption, stability, and dose uniformity. Several examples are provided to illustrate how reducing particle size can impact solubility and bioavailability. Different methods for measuring particle size distribution are also summarized, including microscopic, sieving, sedimentation, and conductivity techniques.
The document discusses micromeritics, which is the study of physicochemical properties of small particles. It describes various fundamental properties of powders like particle size, shape, surface area, as well as derived properties including density, flow properties, and porosity. Common methods for analyzing particle size are discussed, including optical microscopy, sieving, and sedimentation techniques like the Andreasen pipette method. Understanding micromeritics is important for preformulation and formulation development as particle properties influence aspects like drug release, absorption, stability, and dose uniformity.
This document discusses various properties related to micromeretics and powder technology. It begins by explaining the importance of understanding particle size, shape, surface area and other properties in preformulation and formulation development. Various methods for determining these properties are described, including optical microscopy, sieving, sedimentation, and conductivity methods. The document also discusses fundamental properties like size, shape and surface area as well as derived properties of powders including density, porosity and flow properties. Understanding these properties is important for developing solid dosage forms with consistent and uniform drug content.
Powder Technology
Particle analysis in pharmaceuticals
Determination of particle size and surface area
Large scale equipment for powders
Types of powders
Micromeritics study in different formulation • Colloidal dispersion are characterized by
particles that are too small to be seen in the ordinary microscope. • The particles of
pharmaceutical emulsion and suspension and the “fines” of powder fall in the range of the
optical microscope. • Particles having the size of coarser powder , tablet granulation , and
granular salts fall with in the sieve range. Control of particle size and the size range of a drug
can be significantly related to its physical, chemical and pharmacological properties.
Bioavailability, and physical stability in some dosage forms can also be affected by particle
size.Micromeritics is the science and technology of small particles . The unit of particle size
most frequently used in micromeritics is micrometer, also called as a micron.
This document discusses various aspects of micromeritics including particle size, shape, surface area, and methods to characterize these properties. It describes key terms like monodisperse and polydisperse systems. Common methods to determine particle size include optical microscopy, sieve analysis, sedimentation, and conductivity/Coulter counter methods. Each method has advantages and disadvantages and suitable size ranges. Particle properties influence important formulation and drug delivery factors like dissolution, absorption, stability, and dose uniformity.
This document discusses various methods for measuring particle size, including microscopy, sieving, sedimentation techniques, the Coulter counter method, and laser diffraction. It provides details on each method, such as the typical particle size ranges they measure, advantages and disadvantages of each approach.
Assignment 01: Discuss the different ways of particle diameter expression. Also to calculate the equation of particle number for 1 gram of powder sample. A little assignmen on the topic based on micromeritics.
Micromeritics refers to the science and technology of small particles. It deals with particle size, size distribution, shape, surface area, and pore size. Knowledge of these properties is important in pharmacy because particle size affects drug release from dosage forms and stability of suspensions, emulsions, and tablets. It also influences flow properties and uniformity of drug fill in tablets and capsules. Smaller particle sizes increase dissolution and absorption rates for some drugs. Common methods to determine particle size include sieving, sedimentation, light scattering, and electrical sensing using a Coulter Counter.
Microspheres are small spherical particles, with diameter 1 µm to 1000 µm.
They are spherical free flowing particles consisting of proteins or synthetic polymers which are biodegradable in nature.
Microspheres Preparation and Evaluations.pptxRAHUL PAL
This document discusses microspheres, including their definition, classification, preparation methods, evaluation, applications, and marketed preparations. Microspheres are spherical particles between 1-1000 μm in size that can be made of polymers, proteins, or synthetic materials. Common preparation methods include single/double emulsion, solvent evaporation, phase separation coacervation, spray drying, and polymerization. Microspheres are evaluated based on particle size, drug entrapment efficiency, swelling index, and in vitro drug release. They have applications in oral, nasal, ocular, and transdermal drug delivery due to their ability to provide sustained release and target drug delivery.
Microspheres Preparation and Evaluations.pdfPrachi Pandey
This document discusses microspheres, including their definition, classification, preparation methods, evaluation, applications, and marketed preparations. Microspheres are spherical particles between 1-1000 μm in size that can be made of polymers, proteins, or synthetic materials. Common preparation methods include single/double emulsion, solvent evaporation, phase separation coacervation, spray drying, and polymerization. Microspheres are evaluated based on particle size, drug entrapment efficiency, swelling index, and in vitro drug release. They have applications in oral, nasal, ocular, and transdermal drug delivery due to their ability to provide sustained release and target drug delivery.
The document discusses micromeritics, which is the science and technology of small particles. It covers particle size and size distribution, methods for determining particle size such as microscopy, sieving, and sedimentation. It also discusses density and flow properties of powders. Particle size affects properties like drug release, absorption, stability, and dose uniformity. Methods are needed to characterize particle size distribution and average particle size. Flow properties tests include Carr's index and Hausner ratio. Factors like particle size, shape, surface forces, and additives impact flow.
Micromeritics is the science and technology of small particles. Knowledge of particle size and size distribution is important in pharmacy because it affects the physical, chemical, and pharmacological properties of drugs. Particle size can influence drug release from dosage forms and absorption. There are several methods to determine particle size, including optical microscopy (0.2-100 μm), sieving (40-9500 μm), and sedimentation (0.08-300 μm). Density and flow properties of powders are also important considerations that impact manufacturing processes.
Micromeritics is the science of small particles, typically less than 1 mm in size. Key aspects include particle size, size distribution, shape, and surface area, which influence properties of powders and their performance in pharmaceutical dosage forms. Common methods to measure particle size include microscopy, sieving, sedimentation, and laser diffraction. Factors like size, shape, surface texture, moisture content and addition of glidants can impact flow properties which are important for manufacturing processes that require powder flow like tableting.
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Micromeritics unit 4 physical pharmaceutics sem.4 b.pharm
1. R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of Pharmaceutics,VCP,Erode.
1
2. MICROMERITICS
MICROMERITICS is the science and technology of small
particles.
The unit of particle size used in the micrometer
(µm), micron (µ).
As particle size decreases ↓, area increases ↑
R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of Pharmaceutics,VCP,Erode.
2
3. Applications in Pharmacy
Release and dissolution.
Absorption and drug action.
Physical stability.
Dose uniformity.
R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of Pharmaceutics,VCP,Erode.
3
4. Size and the size range
Size and the size range of particles are importance
in pharmacy because the size and surface area of a
particle related to the physical, chemical and
pharmacologic properties of a drug.
The particle size of a drug can affect its release
from dosage forms that are administered orally,
parenterally, rectally and topically.
In the area of tablet and capsule manufacture,
control of the particle size is essential in the
necessary flow properties and proper mixing of
granules and powders.
R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of Pharmaceutics,VCP,Erode.
4
5. Particle Size and Size Distribution
In a collection of particles of more than one
size, two properties are important,
1. The shape and surface are of the individual
particles.
2. The particle size and size distributions (The
size range and number or weight of particles).
R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of Pharmaceutics,VCP,Erode.
5
6. Particle Size
The size of a sphere is readily expressed in terms of its
diameter.
The Surface diameter, ds , is the diameter of a sphere
having the same surface area as the particle.
The Volume diameter, dv , is the diameter of a sphere
having the same volume as the particle.
The Projected diameter, dp , is the projected diameter
of a sphere having the same observed area as the
particle.
The Stokes diameter, dst, is the diameter which
describes an equivalent sphere undergoing
sedimentation at the same rate as the asymmetric
particle.
R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of Pharmaceutics,VCP,Erode.
6
7. Particle Size
Any collection of particles is usually
polydisperse. It is therefore necessary to know not
only the size of a certain particle, but also how
many particles of the same size exist in the sample.
we need an estimate of the size range present and
the number or weight fraction of each particle size.
This is the particle-size distribution and from it we
can calculate an average particle size for the
sample.
R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of Pharmaceutics,VCP,Erode.
7
8. Particle Size Distribution
When the number or weight of particles lying
within a certain size range is plotted against
the size range or mean particle size, a so-
called frequency distribution curve is
obtained.
This is important because it is possible to
have two samples with the same average
diameter but different distributions.
R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of Pharmaceutics,VCP,Erode.
8
9. MEAN PARTICLE SIZE
Mean value of particle size distribution
The value of each particle size should be multiplied
by the normalized particle amount (difference %)
and the result should be divided by the total
normalized particle amount (100%).
R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of Pharmaceutics,VCP,Erode.
9
10. Properties of Powders
• 1. Fundamental properties :-
These properties relate to the individual
particle.
• 2. Derived properties :-
They are dependent on fundamental
properties & define the factors relating to
their measurement.
R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
10
11. Fundamental properties
1. Particle size and size distribution
2. Particle shape
3. Particle surface area
4. Particle weight 5. Particle
R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
11
12. Derived properties:
• 1. Density of powders
(a) Bulk density
(b)Tapped density
(c) Granular density
(d)True density
2. Flow properties of powders
3. Porosity
4. Bulkiness
R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
12
13. Fundamental properties of powders
Particle size
Denoted in micrometers (formerly called as microns)
One micrometer is equal to 10-3 mm or 10-6 m
One millimicrometer is called one nanometer (nm)
One nanometer = 10-9 m or 10-6 mm or 10-3 µm
1 m = 1000 mm
1 mm = 1000 µm
1 µm = 1000 nm R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
13
15. Optical Microscopy
• Particle size in the range of 0.2 – 100 µm can be
measured.
• This method gives number distribution which can
be converted to weight distribution Optical
microscope lens has limited resolving power.
• Advanced microscopes have better resolving
power and can measure size in nano range:
Ultra microscope, Electron microscope-
Scanning Electron microscope (SEM), Transmission
Electron microscope (TEM)
R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
15
16. R.VIJAYAKUMAR ., M Pharm., Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
16
17. Procedure:
1. Eye piece of the microscope is fitted with a
micrometer.
2. This eye-piece micrometer is calibrated using a
standard stage micrometer.
3. The powder sample is dispersed in a suitable
vehicle in which it does not dissolve and its
properties are not altered. (eg. water, paraffin oil.)
4. This sample is mounted on a slide and placed on
the stage under the objective of microscope.
5. Around 625 particles are visualized. their
diameter is noted and mean is computed.
R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
17
18. Advantages
One can view particles
Any aggregates detected
Contamination of particles detected
Use of cover slip for arresting motion of particles
Easy and simple method.
Disadvantages
Length and breadth can be detected but depth
or thickness of particles cannot be measured .
Slow- time consuming , tedious, inaccurate.
Number of particles to be measured is more
sample required.
R.VIJAYAKUMAR ., M Pharm., Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
18
19. Application
• Particle size analysis in suspensions, aerosols,
globule size analysis in emulsion.
R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
19
20. 2. Sieving Method
• Sieving method is an ordinary and simple method.
• It is widely used as a method for the particle size
analysis
• Sieve analysis is usually carried out using dry
powders.
Although, for powders in liquid suspension or
which agglomerate during dry sieving, a process of
wet sieving can be used.
R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
20
22. • Sieving method directly gives weight distribution.
• It find application in dosage form development of
tablets and capsules.
• Normally, 15% of fine powder should be present in
granulated material to get proper flow of material
and achieve good compaction.
• Thus percent of coarse, moderate, fine powder is
estimated by this method.
R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
22
23. PROCEDURE :
• Sieve analysis utilizes a wire mesh made of brass,
bronze or stainless steel with known aperture (hole)
diameters which form a physical barrier to particles.
• The standard sieve sizes are as per the
pharmacopoeia
• Most sieve analyses utilize a series, stack (layer) of
sieves which have the coarser mesh at the top of
the series and smallest mesh at the bottom above a
collector tray
(The mesh size goes on decreasing from
top to bottom) R.VIJAYAKUMAR ., M Pharm., Asst Professor,Dept
of Pharmaceutics,VCP,Erode.
23
24. Operational principle:
• A sieve stack usually comprises 6-8 sieves.
• Powder is loaded on to the coarsest sieve of the
stack and then it is subjected to mechanical
vibration for specified time, eg 20 minutes.
• After this time, the powder retained on each sieve
is weighed
• The particles are considered to be retained on the
sieve mesh with an aperture corresponding to the
sieve diameter.
• The size is estimated as per the standards given in
pharmacopoeia
R.VIJAYAKUMAR ., M Pharm., Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
24
25. • Care should be taken to get reproducible results.
• The type of motion, time of operation, speed,
weight of powder should be fixed and standardized.
Advantages-
Inexpensive,
Simple,
Rapid &Reproducible results (if
parameters are standardized)
Disadvantages-
lower limit is 50 microns
Powder if moist, can cause clogging of apertures
Attrition between particles during the process may
cause size reduction giving inaccurate results.
R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
25
26. SEDIMENTATION METHOD
(range: 0.08-300 µm)
• In this method particle size can be determined by
examining the powder as it sediments out.
• Several methods has based on the sedimentation ,
Pipette method
Balance method
Hygrometers method
• By measuring the terminal settling velocity of
particles through a liquid medium in a gravitational
centrifugal environment using by Andreasen
appartus. R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
26
27. Principle
• Particle size analysis by sedimentation method
can be divided into two main categories
according to the method of measurement
used.
• Measurement of particle in a retention zone
and non-retention measurement zone.
An example of a non-retention zone
measurement is known as the pipette
method.
R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
27
28. Andreasen Pipette Method
• One of the most popular of the pipette methods
was that developed by Andreasen and Lundberg
and commonly called the Andreasen pipette.
• In this method , known volumes of suspension are
drawn off and the concentration differences are
measured with respect to time.
• It involves measuring the % of solids that settle
with time in a graduated vessel.
R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
28
29. Sample Preparation
• Powder is dispersed in a suitable solvent
• If the powder is hydrophobic, it may be
necessary to add dispersing agent to aid
wetting of the powder.
• In case where the powder is soluble in water
it will be necessary to use non- aqueous
liquids or carry out the analysis in a
gas(aerosols).
R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
29
30. Construction
• The Andreasen fixed-position pipette consists of
a 200 mm graduated cylinder which can hold
about 500 ml of suspension fluid.
• A pipette is located centrally in the cylinder and is
held in position by a ground glass stopper so that
its tip coincides with the zero level.
• A three way tap allows fluid to be drawn into a
10 ml reservoir which can then be emptied into a
beaker or centrifuge tube.
R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
30
31. R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
31
32. Method
• A 1% suspension of the powder in a suitable liquid
medium is placed in the pipette.
• At a given intervals of time, samples are withdrawn
from a specified depth without disturbing the
suspension.
• The amount of powder can be determined by
weight following drying or centrifuging;
alternatively, chemical analysis of the particles can
be carried out.
R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
32
33. • A pipette is located centrally in the cylinder and is
held in position by a ground glass stopper so that its
tip coincides with the zero level.
• A three way tap allows fluid to be drawn into a 10
ml reservoir which can then be emptied into a
beaker or centrifuge tube.
• The amount of powder can be determined by
weight following drying or centrifuging.
• The data of cumulative weight is used for the
determination of particle weight distribution,
number distribution etc..
R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
33
34. • The particle size is determined in terms of stokes’
diameter (the diameter of a particle measured
during sedimentation at constant rate) using
modified Stokes' equation.
R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
34
35. • The second type of sedimentation size analysis,
using retention zone methods, also uses Stokes'
law to quantify particle size.
• One of the most common retention zone
methods uses a sedimentation balance.
• In this method the amount of sedimented
particles falling on to a balance pan suspended in
the fluid is recorded.
• The continual increase in weight of sedimentation
of the particles.
R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
35
36. Kinetic method/ Conductivity methods
• There are various subtypes
Two popular methods are-
• Electrical stream sensing zone method (Coulter
counter).
• Powder samples are dispersed in an electrolyte to
form a very dilute suspension.
• The suspension is usually subjected to ultrasonic
agitation to break up any particle agglomerates.
• A dispersant may also be added to aid particle
deagglomeration. R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
36
37. Method
• The particle suspension is drawn through an
aperture accurately drilled through a sapphire
crystal set into the wall of a hollow glass tube.
• Electrodes, situated on either side of the aperture
are surrounded by an electrolyte solution.
• These electrodes monitor the change in electrical
signal which occurs when a particle momentarily
occupies the orifice and displaces its own volume of
electrolyte.
R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
37
38. • The volume of electrolyte fluid which is displaced
in the orifice by the presence of a particle causes
a change in electrical resistance between the
electrodes which is proportional to the volume of
the particle.
R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
38
39. • Advantage:
Particle size ranging from 0.5 – 500 microns
Gives number distribution, Particle volume measured
and can be converted to diameter.
Accurate, sensitive, fast technique.
4000 particles per second can be counted.
• Disadvantage:
Expensive
R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
39
40. • Laser light scattering methods It is based on
the principle of change in light intensity.
The measurement of this change in light
intensity gives estimate of particle size.
R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
40
41. Surface area
• Surface area of a powder can be calculated using particle size
data obtained from any suitable method.
Specific surface area i.e. surface area per unit weight (Sw )
or unit volume (Sv ) can be estimated as follows:
• Sv = surface area of particles / volume of particles
• Surface area is an important parameter as the bioavailability
of certain drugs is dependant on surface area.
• eg. Bephenium (anthelminitic), Griseofulvin (antifungal)- if
the surface area is less than specified, the absorption
decreases. R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
41
42. Surface Area Determination
Adsorption method
• Surface area is most commonly determined based on
Brunauer-Emmett-Teller (BET) theory of adsorption.
• Most substances adsorb a monomolecular layer of gas under
certain conditions of partial pressure of gas and temperature.
• The adsorption process is carried out at liquid nitrogen
temperatures -196˚C.
• Once surface adsorption has reached equilibrium, the sample
is heated at RT and Nitrogen gas is desorbed. Its volume is
measured.
• As each N2 mol. occupies fixed area, one can compute surface
area of pre-weighed sample.
R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
42
43. R.VIJAYAKUMAR ., M Pharm., Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
43
44. Air Permeability method
o Powder is packed in sample holder
o Packing appears as series of capillaries
o Air is allowed to pass through the capillaries at
constant pressure
o Resistance is created as air passes through
capillaries thus causing pressure drop.
o Greater the surface area greater the resistance
o Air permeability is inversely proportional to the
surface area.
R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
44
45. Particle Shape Determination
Particle shape also has influence on surface
area, flow properties, packing and compaction
of the particles.
Spherical particles have minimum surface area
and better flow properties. Shape can also
have influence on rate of dissolution of drugs.
R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
45
46. R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
46
47. Techniques of Particle Shape
Determination
Microscopy method
Light scattering method
R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
47
48. Derived properties of powders
• Size or diameter is a fundamental property of a
particle.
• Volume, density, porosity, flow property etc. are
the properties derived from fundamental
properties.
e.g. Volume can be calculated from the
diameter of the particle (4/3 πr 3 ).
The derived properties can also be calculated
without the use of fundamental properties.
R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
48
49. Density of powders
• Density is defined as weight per unit volume
(W/V).
During tapping, particles gradually pack more
efficiently, the powder volume decreases and the
tapped density increases.
Types of Density
1. True density
2. Bulk density
R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
49
50. 1. True density: The true density or absolute density
of a sample excludes the volume of the pores and
voids within the powder sample.
2. Bulk density: The bulk density value includes the
volume of all of the pores within the powder
sample.
R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
50
51. R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
51
52. DENSITY
• Apparent bulk density- is determined by pouring
presieved (40#) bulk drug into a graduated
cylinder via a funnel and note the volume as is
(g/ml) without subjecting to any external force.
• Tapped density: The cylinder is subjected to
fixed no. of taps on a mechanical tapper
apparatus (approx. 100) until the powder bed has
reached minimum. (useful for determining the
appropriate size for capsule formulation).
R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
52
53. Bulk Density Apparatus
R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
53
Bulk density = Mass of the powder
/Bulk volume
Tapped bulk density = Mass of the
powder/ Tapped Bulk
volume
54. Applications
Decides the size of the capsule based on bulk and
tapped volume of a given sample.
Higher the bulk volume, lower the bulk density and
bigger the size of the capsule.
Helps to decide proper size of a container or packing
material.
For Light powders
When particles packed loosely ,Lots of gaps
between particles
Bulkvolume increases Light powders have high bulk
volume, hence low density.
R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
54
55. Applications
Decides the size of the capsule based on bulk and
tapped volume of a given sample.
Higher the bulk volume, lower the bulk density and
bigger the size of the capsule.
Helps to decide proper size of a container or packing
material.
For Light powders
When particles packed loosely ,Lots of gaps
between particles
Bulkvolume increases Light powders have high bulk
volume, hence low density.
R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
55
56. Flow properties of Powder
• Pharmaceutical powders may be broadly
classified as free-flowing or cohesive.
• Most flow properties are significantly affected
by changes in particle size, density,
electrostatic charges, adsorbed moisture.
• Good flow property is required for easy and
uniform flow from hopper to die cavity
ensuring accurate weight and dose for tablets.
R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
56
57. R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
57
58. • Angle of repose is calculated for estimating flow
properties.
It is defined as the maximum angle possible
between the surface of a pile of the powder and the
horizontal plane.
R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
58
59. R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
59
60. R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
60
61. Packing properties (Porosity)
• It is the ratio of the volume of voids between particles,
plus the volume of pores, to the total volume occupied
by the powder, including voids and pores.
• A set of particles can be filled into a volume of space in
different ways.
This is because by slight vibration, particles can
be mobilized and can occupy a different spatial volume
than before.
• This changes the bulk volume because of
rearrangement of the packing geometry of the
particles.
such geometric rearrangements result in a
transition from loosely packed particles to more tightly
R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
61
62. • The bulk density of a powder is always less than the
true density of its component particles because the
powder contains inter particle voids.
• Thus, powder can possess a single true density but
can have many different bulk densities, depending
on the way in which the particles are packed and
the bed porosity.
R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
62
63. R.VIJAYAKUMAR ., M Pharm.,
Asst Professor,Dept of
Pharmaceutics,VCP,Erode.
63