MICROMERITICS Flashcards
The science and technology of small particles
MICROMERITICS
MICROMERITICS
The unit of particle size used most frequently is_____,also called _____, equal to 10-6 m, 10-4 cm, 10-3 mm
micrometer (μm);micron; 10-6 m, 10-4 cm, 10-3 mm
IMPORTANCE IN PHARMACY
¡ Particle can be related in a significant way to the
physical, chemical, and pharmacologic properties
of a drug.
¡ Release from dosage forms
¡ The successful formulation of suspensions,
emulsions, and tablets
¡ In the area of tablet and capsule manufacture
In a collection of particles of more than one
size, two properties are important, namely
the shape and surface area of the
individual particles, and
Ø the size range and number or weight of
particles present and, hence, the total
surface area.
METHODS FOR DETERMINING PARTICLE
SIZE
¡Microscopy
¡Sieving
¡Sedimentation
¡Determination of particle volume
- OPTICAL MICROSCOPY
¡ _______ can be used for
particle-size measurement in the range of ____ to about ____”
Ordinary microscope; 0.2 -100 micron
OPTICAL MICROSCOPY
OPERATIONAL USE
¡Accordingly to the _______ an ____OR____,_____,____
is _____ on a slide or ruled cell
and placed on a mechanical stage.
Microscopic methd; emulsion or
suspension, diluted or undiluted; mounted
3 measurements for optical microscopy:
a. Ferret Diameter
b. Martin Diameter
c. Projected Area of the
Circle
◼ 2 tangents separated by
the longest distance
a. Ferret Diameter
◼ distance that will bisect
the particle into halves
b. Martin Diameter
◼ diameter of the circle that
will enclose the particle
c. Projected Area of the
Circle
a. Ferret Diameter
◼_____ separated by
the ____
2 tangents;longest distance
b. Martin Diameter
◼ distance that will _____
the particle into_____
bisect; halves
c. Projected Area of the
Circle
◼ diameter of the circle that
will _____ the particle
enclose
DISADVANTAGES OF OPTICAL MICROSCOPY
◼ Diameter is obtained from only two dimensions of the particle: length and breadth.
◼ No estimation of the depth (thickness) of the particle is ordinarily available.
◼ The number of particles that must be counted (300 to 500) to obtain a good emulsion of the distribution makes the method somewhat slow and tedious.
ADVANTAGES OF OPTICAL MICROSCOPY
◼The presence of agglomerates and particles of more than one
component may often be detected.
◼ This method uses series of standard sieves calibrated by National Bureau of Standards
Sieving
Sieving
◼ This method uses series of ______ calibrated by ______
standard sieves;National Bureau of Standards
◼ Sieves are generally used for ________; if extreme care is used, however, they may be employed for screening material as fine as____-
grading coarser particles; 44 micron (#325 sieve)
SIEVING ERRORS ARRIVED FROM:
¡Sieve loading
¡Duration and intensity of
agitation
MW
determination of high polymers
Ultracentrifugation:
Ultracentrifugation: ____
determination of _____
MW; high polymers
`
◼Proper _____must be found for each sample that will keep the particles _____ and_____ as they fall thru the medium.
deflocculating agent; free; separate
OTHER METHODS BASED ON
SEDIMENTATION:
Ø
Pipette method
Ø Balance method
Ø Hydrometer method
550-mL vessel containing a 10-
mL pipette sealed into a ground
glass stopper
Andreasen Apparatus
Andreasen Apparatus
_____ vessel containing a ____ pipette sealed into a _______
550-mL; 10-mL; ground glass stopper
Andreasen Apparatus
When the pipette is place in
the cylinder, its _________ below the surface of the
suspension
lower tip is 20
cm
this instrument
operates the principle that when a
particle suspended in a conducting
liquid passes thru a small orifice on
either side of which are electrodes, a change in electric resistance occurs
Coulter counter
Coulter counter
this instrument
operates the principle that when a
particle suspended in a conducting
liquid passes thru a small orifice on
either side of which are _____, a change in ________ occurs
electrodes; electric resistance
Automatic Particle Counters:
¡ Coulter Counter:
¡ HIAC/Royco Instrument:
¡ Gelman Counter:
Coulter counter principle:
Electric resistance
HIAC/Royco Instrument principle:
Light blockage
Gelman Counter principle:
Faraday-Tyndall Effect
ADVANTAGE OF PARTICLE COUNTERS
¡ For study of particle growth and
dissolution; study of the effect of
antibacterial agents on the growth
of microorganisms
¡the simplicity of its operation and
its reproducibility
LIMITATIONS OF PARTICLE COUNTERS:
¡ As in microscopic counts, the machine cannot
distinguish between _______
even between _____
¡ Any reasonably _____ in the solution will be counted.
¡ There is also the ______ of buying the
counter, which can cost many thousands of
dollars.
living or dead cells
dust and bacteria.
sized particle
expense
¡ A sphere has minimum surface area _____
per
unit volume.
¡ The more ____, the
greater the _____
asymmetric a particle;surface area per unit volume
METHODS FOR DETERMINING SURFACE AREA
¡ Two methods are commonly available that permit
_____ of surface area.
direct calculation
METHODS FOR DETERMINING SURFACE
AREA:
¡ 1) Adsorption Method
2. AIR PERMEABILITY METHOD
¡ the amount of a gas or liquid solute that is
adsorbed on the samples of powder to form a
monolayer is the direct function of the surface area
of the sample.
¡ 1) Adsorption Method
¡ 1) Adsorption Method
¡ the amount of a gas or liquid solute that is
______ on the samples of powder to form a
______ is the direct function of the surface area
of the sample.
adsorbed; monolayer;
theory of
adsorption.
Brunauer-Emmett-Teller (BET)`
¡Depends on the fact that the rate at
which a gas or liquid permeates
a bed of powder is related, among
other factors, to the surface area
exposed to permeate.
- AIR PERMEABILITY METHOD
- AIR PERMEABILITY METHOD
¡Depends on the fact that the rate at
which a gas or liquid _____
a bed of powder is related, among
other factors, to the surface area
exposed to permeate.
permeates
Materials of high specific area may have _______&_____ that adsorb gases and vapors, such as water, into their______.
cracks and pores; interstices
Relatively powdered drugs may dissolve more or less in aqueous medium depending upon their______.
adsorption of moisture or air
DERIVED PROPERTIES OF POWDERS
¡ Porosity
¡ Packing arrangement
¡ Densities of particles
¡ Bulkiness
¡ Flow properties
¡ Compaction
¡ The ratio of the void volume to
the bulk volume
POROSITY
POROSITY
¡ The ratio of the _____ volume to the_____ volume
void; bulk
¡ Example: zinc oxide placed in
graduated cylinder where the
total volume is noted.
¡ Bulk volume
¡ This is known as the volume
of spaces between particles
¡ Void Volume
¡In the case of nonporous powder (no
internal pores or capillary spaces),
bulk volume of the powder is equal
to:
Øthe true volume of the solid particles plus the volume of the spaces between
particles
nonporous powder:
(no
internal pores or capillary spaces),
______ can assume either one
of two ideal packing arrangement
Powder beds or uniform sized
spheres
PACKING ARRANGEMENT:
Ø Closest or rhombohedral
Ø Loosest or cubic packing
¡ Since particles may be _____ in one case, and _____ in another, one must express
densities with great care
hard and
smooth
rough and
spongy
Density of the material itself,
exclusive of the voids and intra-particle pores larger
than molecular or atomic dimensions in the crystal
lattices
True Density:
Determined by the displacement
of mercury which does not penetrate at ordinary
pressures into pores smaller than about 10 micron
Granule Density:
Determined from the bulk volume
Bulk Density:
Specific bulk volume, the reciprocal
of bulk density is called
bulkiness or
bulk
Bulkiness _____ with a ____in particle size.
increases;decrease
A bulk powder is somewhat
analogous to a
non-Newtonian liquid,
A bulk powder is somewhat
analogous to a non-Newtonian liquid,
which exhibits _____ and
sometimes _____, the particle
being influenced by attractive forceso varying degrees
plastic flow
dilatancy
¡Accordingly, powders may be
free-
flowing or cohesive
To improve flow characteristics,
materials termed ____ are frequently
added to granular powders
glidants
(Mg stearate and talc)
is one of the factors involving in
mixing materials to form a
powder blend.
ability of a powder to flow
______, is an important
pharmaceutical operation involved in
the preparation of many dosage
forms, including tablets and capsules
ØMixing, and the prevention of
unmixing
Compressed tablets: ______found that when
powders were compacted under a pressure of about 5
kg/cm2,
Neumann
Compressed tablets: Neumann found that when
powders were compacted under a pressure of about 5
kg/cm2, the porosities of the powders composed
of ______ (sodium carbonate, for example)
were higher than the porosities of powders in
_____, as determined by _____.
rigid particles
closest packing
tapping
experiments
Compressed tablets: Neumann found that when
powders were compacted under a pressure of about 5
kg/cm2, the porosities of the powders composed
of rigid particles (sodium carbonate, for example)
were higher than the porosities of powders in
closest packing, as determined by tapping
experiments. Hence, these powders were ______, that
is contraction, under the influence of stress
dilatant
In the case of soft and spongy
particle (kaolin), however, the
particles deformed on ______,
and the porosities were _____than
other tapping the powder down to its
condition if ______
compression
lower
closest packing
Volume occupied by the powder
BULK VOLUME
Volume of the spaces between the particle
VOID VOLUME
The ratio of the void volume to the bulk volume
POROSITY
Powder beds or uniform sized spheres can assume either one of
two ideal packing arrangement
Ø Closest or rhombohedral
Ø Loosest or cubic packing
PACKING
ARRANGEMENT
Reciprocal of bulk density
BULK SPECIFIC
VOLUME
From the true and granule density
Intraparticle porosity
Relative volume of interspace voids to the bulk volume of the
powder.
Interspace/ void
porosity
