Lecutre 1 Powders and Granules Flashcards
What is a powder?
A dry substance composed of finely divided particles which may be used for internal or external use.
What can particle size effect?
Dissolution rate (Stoke’s Law), suspendability of suspensions (accurate dosing), uniformity of mixtures in liquids, penetrability of particles for inhalation (narrow window 1-10 microns), lack of grittiness for dermatologicals.
Why does particle size matter?
- Uniform particle size aids in mixing and distribution.2. Migration may occur with differences in particle size.3. Differences may change the color intensity of a powder.4. Especially important in dermatologicals.
What is the study of small particles?
Micromeritics.
Micromeritics includes the study of …
particle size and particle size distribution, uniformity, morphololgy, flow, porosity, volume, density, ,compatibility with other formulation components.
What is the purpose of particle size analysis?
To obtain quantitative data on the size, distribution an morphology of powders.
What size range can powders be?
Extremely coarse (10 mm) to extremely fine (1 micron or less)
What are the USP descriptive terms?
very coarse, coarse, moderately coarse, fine, and very fine
Particle Size and Analysis
Very Coarse #8 Sieve 2,360 micrometerCoarse #20 Sieve 850 micrometerMod. Coarse #60 Sieve 425 micrometerFine # 60 Sieve 250 micrometerVery Fine #80 Sieve 180 micrometer
What are the five different methods of particle size analysis?
Sieve Analysis, Microscopy, Sedimentation Rate, Laser Light Scattering or Diffraction, Cascade Impaction.
How is Sieve Analysis preformed?
Particles are passed by mechanical shaking through a series of sieves of known and successively smaller size.
How does Microscopy determine particle size?
Particle size is determined by visual observation with the use of calibrated grid background or other measuring device.
What does a cascade impactor measure particle size for?
For inhalation dosage forms
What is powder flow impacted by?
size, shape, porosity
What is powder flow characterized by(tests)?
angle of repose, and carr index(compressibility Index)
What does Angle of Repose estimate and how is it measured?
Estimates flow properties and is a measure of the angle formed when powder is allowed to flow freely from a known height. Tan 0 = h/r
If a powder has a low angle of repose what does this mean?
The powder flows freely
What does tapped and bulk density determine?
Powder flow and compressibility
What is tapped and bulk density useful for?
It helps determine storage needs.
What is the CARR INDEX equation?
% compressibility = (Tapped Density - Bulk Density) / Tapped Density x 100As Zakiya says throw back Thursday
A compressibility range of 5-15 means the flow is?
Excellent (free flowing)
A compressibility range of 12-15 means the flow is?
Good (free flowing powdered granules)
A compressibility range of 18-21 means the flow is?
Fair (powdered granules)
A compressibility range of 23-28 means the flow is?
Poor (very fluid powders)
A compressibility range of 28-35 means the flow is?
Poor (fluid cohesive powders)
A compressibility range of 35-38 means the flow is?
Very poor (fluid cohesive powders)
A compressibility range greater than 40 means the flow is?
Extremely poor (cohesive powders)
What is the process of reducing the particle size of a solid substance to a finer state of subdivision?
comminution
What are the reasons to reduce particle size?
- Facilitate crude drug extraction2. Increase the dissolution rates of drugs3. Aid in the formulation process4. Enhance absorption
What are extemporaneous processes that can have the affect of communition?
TriturationPulverizationLevigation
What is continued rubbing of a solid in a mortar with a pestle to reduce the particle size?
Trituration
What is communition by utilizing a solvent that can be easily removed?
Pulverization
What is communition by triturating while moistened with a liquid in which the powder is insoluble?
Levigation
What are the different ways to reduce particle size industrially?
Milliing (Ball Mills, Roller Mills, Cutter Mills, Hammer Mills, Colloid Mills, Fluid Energy Mills), Lyophilization, Spray Drying
What are the 5 different ways to blend powders?
Spatulation, Trituration, Tumbling, Specialized equipment, and Geometric Dilution.
What is spatulation?
Mixing of powders on an ointment slab or pad using a spatula; no particle size reduction.
What is trituration?
Continued rubbing of a solid in a mortar with a pestle to reduce the particle size.
What is tumbling?
Uses clear glass or plastic bottles and zipper sealed plastic bags to mix powders.
What type of blending is used when blending two or more powders of unequal quantities to ensure that small quantities of usually potent drugs are uniformly distributed throughout the powder mixture?
Geometric Dilution
What do you use to blend powders industrially?
Tumblers(double cone blender and twin shell blender) and paddle blenders
What are the 4 factors that have to be considered when blending?
size, shape, density, electrostatic forces
What is a powder used to clean teeth?
Dentrifrices
What is a powder intended for application to body cavities?
Insufflations
What are substances that absorb moisture from the air?
Hygroscopic
What are substances that absorb moisture from the air to the extent that they liquefy by partially or wholly forming a solution?
Deliquescent
What are crystalline substances that become powdery and liberate their water of hydration when they are manipulated or stored under conditions of low relative humidity?
Efflorescent Powders
What is a mixture of certain components with a melting point less than room temperature; thus, they liquefy when in close and prolonged contact?
Eutectic Mixtures
How can you avoid eutectics?
Dispense powders separately, add an absorbent powder, keep ingredients separated as much as possible, make the eutectic, then add absorbent to incorporate the liquid.
What are some absorbent powders that can be used to avoid eutectics?
talc, starch, lactose, calcium phosphate
What are granules?
Prepared agglomerates of powdered materials ranging from 4 to 10 mesh in size.
How do you prepare a granule?
Prepared by moistening blended powders and by passing this mass through a screen or a granulator. Granules are then air or oven dried. Flavors can be sprayed on the granules and then dried.
What is an effervescent granule?
Contains mixtures of citric acid, tartaric acid, or sodium biphosphate with a bicarbonate and a medicinal agent. The carbonated solution is a pleasant vehicle and lessens the bitter and salty taste of salts.
