Particle sizing analysis 1 Flashcards
What is particle size analysis important in?
Particle size greatly influences physical properties of Pharmaceuticals:
Powder flow during handling & manufacturing solid dosage forms
Powder mixing: Drug content uniformity
Dissolution: small particles dissolve faster than larger particles (so better bioavailability)
Aerosol deposition
Stability (dispersions)
Safety & efficacy of medicinal products
Small particle size means
improved dissolution, increased specific surface area
dissolve more rapidly than large ones
Specific surface area (or surface area to volume ratio)
3/r
How do we decrease particle size
Milling
Measuring particle size - what are the different methods
equivalent diameters: projected area diameter, Feret’s diameter, Martin’s diameter
What is equivalent diameter
This imaginary sphere is called an equivalent sphere.
Its size (its diameter) is called the equivalent diameter.
What is projected area diameter
The projected area diameter is based on a circle of area equivalent to that of the projected image of a particle
DRAW PIC TOO!
What is ferets diameter
The (mean) value between pairs of parallel tangents to the projected outline of the particle
What is Martin’s diameter
The (mean) chord length of the projected outline of the particle
Particle size distribution - what do we use
particle size and population density (frequency) histogram, cumulative distribution
Histogram- what does it reflect
The histogram would reflect the distribution of particle sizes.
A representation of this type is called a frequency histogram
What does cumulative distribution show
Which shows how much
material lies above or below
a particular size.
