Term
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Definition
| The science and technology of small particles |
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Term
| Are all particles spherical? |
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Definition
| No, they come in all forms and shapes |
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Term
| Do all particles in the same powder have the same size? |
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Definition
| No, in general there is a size range unless prepared by specialized technology |
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Term
| How is particle area diameter measured? |
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Definition
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Term
| How is particle volume diameter measured? |
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Definition
| Laser diffraction, light obscuration, coulter culture |
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Term
| How is particle Stokes' diameter measured? |
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Definition
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Term
| How is particle equivalent surface diameter measured? |
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Definition
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Term
| How is particle aerodynamic diameter measured? |
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Definition
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Term
| In to measure an irregular particle, what is a Feret diameter? |
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Definition
| The diameter from the tip to the tip, as long as possible |
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Term
| In to measure an irregular particle, what is a Martin diameter? |
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Definition
| The diameter between two bisected parts (must measure consistently) |
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Term
| In to measure an irregular particle, what is a projected diameter? |
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Definition
| The diameter of a circle drawn around the particle |
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Term
| Describe the process of sieving to determine particle size |
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Definition
A "nest" series of USP approved meshes with decreasing diameter are used so the smallest fall to the bottom
Size expressed as undersize, oversize, and mean particle size |
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Term
| Give the equation for the drag force on a particle |
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Definition
(π/6)d3(ps-pf)g
d=diameter
g=gravity
ps=density of particle
pf=density of fluid |
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Term
| Give the equation for terminal velocity of a particle in sedimentation |
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Definition
v=(d^2/18η)(ps-pf)g
(assumes all particles have same density, are spheres, flow laminar, and will not aggregate) |
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Term
| How do you determine if a flow is laminar or turbulent? |
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Definition
If Re is less than .2, the flow is laminar
R=vdpf/η |
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Term
| Describe the steps to analyze particle size via an Andreasen Pipette |
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Definition
1. A suspension is allowed to settle
2. Samples are taken at predetermined times, recording distance of fall
3. Fluid is evaporated from each sample and weight of particles are measured
Particle size is calculated by plotting the cumulative weight undersize |
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Term
| What is the general principle of a sensor of volume diameter? |
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Definition
| A particle is suspended or aerosolized within a region connected to a sensing mechanism that correlates instrument output with the volume of a particle |
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Term
| How does a coulter counter measure volume/diameter? |
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Definition
A particle goes through an orifice and that is translated into voltage that is sent to a screen
(Smaller particles move more) |
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Term
| How does a dynamic light scattering measure volume/diameter? |
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Definition
Movement of particles is detected by a laser sensor that reflects off them
(Smaller particles move more) |
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Term
| How does a laser diffraction measure volume/diameter? |
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Definition
Particles are aerosolized into a region of a laser beam. As particles pass through a lens, the diffraction particle corresponds to size.
Smaller particles give larger diffraction intensity.
Diffraction pattern is different depending on shape. |
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Term
| What are some disadvantages to automated methods to determine particle size? |
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Definition
Does not discriminate between individual particles and aggregates
Instruments are expensive, require maintenance and training |
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Term
| If the ratio of αs/αv =6, what is the particle shape? |
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Definition
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Term
| If the ratio of αs/αv >6, what is the particle shape? |
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Definition
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Term
| How do you calculate Sv, the specific surface area per unit volume? |
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Definition
| Surface area of particles/ volume of particles |
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Term
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Definition
| The adhesion of atoms, ions, biomolecules or molecules of gas, liquid, or dissolved solids to a surface |
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Term
| How is gas adsorption used to calculate surface area? |
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Definition
It assumes that a monolayer of gas (nitrogen/helium) is adsorbed on the surface of particles when a sample of powder is placed on a container where gas is circulated
(Based on the Brunauer Emmett Teller equation) |
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Term
| How does the Air Permeability Method calulate surface area |
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Definition
Surface area is proportional to the pressure drop or permeability of a fluid (usually air) flowing through a compacted sample of powder
(Based on the Kozeny-Carman equation) |
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Term
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Definition
Porosity, or void fraction, is a measure of the void spaces in a powder
A fraction of the volume of voids in each particle over the total volume of the powder |
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Term
| List some things that affect porosity |
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Definition
-Density
-Mixing different powders
-Packing arrangements
-Flow properties
-Compressibility
-Dissolution rate
-Aerodynamic properties |
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Term
| What determines if a liquid will penetrate all the pores in a powder? |
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Definition
| The density of a liquid and if the pores are connected |
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Term
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Definition
| Density for the material itself, without pores or interparticulate spaces |
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Term
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Definition
| Density of the material itself, but considers pores >10μm and inter-particular spaces |
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Term
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Definition
| Relationship of the volume occupied by a determined mass of powder |
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Term
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Definition
| Relationship of the compacted volume occupied by a determined mass of powder |
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Term
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Definition
A gas or liquid machine to measure density based on Archimides' principle:
The weight of the displaced fluid is directly proportional to the volume of the displaced fluid |
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Term
| How is porosity (ε) measured? |
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Definition
ε= 1- (ρ'/ρ)
ρ'= apparent or bulk density
ρ= true density |
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Term
| Where is tapped density especially important? |
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Definition
| In the field of inhalation |
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Term
| What sort of things influence flow properties of powder? |
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Definition
-Size and distribution
-Shape
-Porosity
-Density
-Surface texture |
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Term
| List some reasons why a powder would not flow smoothly |
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Definition
-Capillary forces (moisture)
-Van der Waals Forces
-Mechanical interlocking
-Electrostatic charge |
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Term
| What is the Carr's compressibility index? |
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Definition
A relationship of bulk and tapped density
CCI= (ρT-ρ')/ρT
CCI>30 is a good indication that the powder will make a good tablet |
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Term
| What is the angle of repose? |
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Definition
| A way to measure powder flow, by creating a mountain of powder and seeing how steep the mountain side is |
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Term
| List some ways to regulate powder flow |
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Definition
| Granulation, formulating into particles, add glidants |
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Term
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Definition
Something to add to large or granular powders to make it easier to flow
Ex. magnesium stearate, starch, talc |
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