Particle Size Analysis

Question 1

Particle size distribution
Histogram

Answer 1

• Shows incramental distribution
• Showing number of falling within a given size increment

Question 2

Gemetric mean

Answer 2

• Progression root of first x second

Question 3

Cumulative distribution

Answer 3

• Shows how much material
  lies above or below a
  particular size

Question 4

Normal Histogram analysis

Answer 4

• Particle diameter In normal distribution
• Mean = Median = Mode
• Symetrical about the mean

Question 5

Positive skew Histogram

Answer 5

• Mean > median > mode
• Normalised by replotting
  the equivalent particle diameters using a logarithmic scale

Question 6

Bimodal histogram

Answer 6

• Has two modes of particle distribution
• Not normal or log

Question 7

Cumulative median split of distribution

Answer 7

• 50% split by the median into two half
• Undersize or oversize
• Use for <5 micrometer (undersize)

Question 8

Linear probability graph

Answer 8

• Undersize by particle size
• Straight line means normal distribution

Question 9

Lognormal distibution

Answer 9

• Plot on a cumulative frequency on normal graph
• If curved then plot on a lognormal graph if linear then lognormal

Question 10

Dispersion central tendancy

Answer 10

• Tendency of the particle size to cluster around a particular value
• Mean/mode/median

Question 11

Sample standard deviation

Answer 11

• Must -1 from the sample population (sum of n)

Question 12

Coefficient of variation

Answer 12

• Normalise the standard deviation through division by the mean
• Compare degree of varience between sample population
• SD/mean x 100

Question 13

D90/D10 Ratio

Answer 13

• polydispersity of powders, regardless of the distribution
  model
• 90% / 10% of particle diameter (small closser to 1 more uniform dose)

Question 14

Sieving

Answer 14

• Fill with the sieve pan with powder
• Seal and agitate then weigh
• Large to small mesh & mesh no measures number
• Measure using sive equivalent diameter

Question 15

Possible overestimates of undersize limitation of sieve

Answer 15

• Rod shaped particle size pass through sive verticle
• Hydroscopic could clamp togeth from moisture

Question 16

Microscopy

Answer 16

• Light microscope
• Scanning lectron microscope
• Atomic force microscope

Question 17

What does microscope measure

Answer 17

• Projected area diameter he diameter of acircle having the same area as the particle viewed on surface
• Use martins and feret diameter

Question 18

Limitations of microscope

Answer 18

• May not be representitive of a selection of particles

Question 19

Andreasen pipette

Answer 19

• Stokes law used to determine stokes diameter of particles suspened in powder
• Measurement of settling velocity
• Use centifugation speeding up the measurement

Question 20

Limitations to Andreasen pipette

Answer 20

• Aggregation in water clampring not representitive of size

Question 21

Electrical sensing zone

Answer 21

• Large particle cause resistance and bending when passing through
• Current pulse is directly proportional to the volume of the particle

Question 22

Limitation of electrical sensing zone

Answer 22

• Limited to those particles that can be suitably suspended in an electrolyte solution

Question 23

Laser Diffraction in static light

Answer 23

• Light waves diffracted on the
  particle surface change their direction of travel dependent upon particle size
• Amount of light hitting outer circles used to calculate the ammount of diffracted light on detector

Question 24

Limitations of Laser Diffraction in static light

Answer 24

• Non-spherical causes diffused scatter patterns wich is difficult to accurately interperate

Question 25

Photon correlation spectroscopy

Dynamic light scattering

Answer 25

• Particles diffused in fluid
• Calculation of angle of incidence of scattered lazer can be detected
• Measurement of the brownian motion relates to the size

Question 26

What does photon correlation spectroscopy
measure?

Answer 26

• Measurement of the Hydrodynamic diameter
• This measurement shows the diameter of a sphere that diffuses at the same rate in liquid as the particle

Question 27

Mie Theory

Answer 27

The Mie model takes into account both diffraction and diffusion of the light around the particle in its medium

Question 28

High intensity particle shown on spectroscopy graph

Answer 28

• A high intensity particle shows more scattered light with slow fluctuations

Question 29

Low intensity particle shown on spectroscopy graph

Answer 29

• Low intensity causes rapid fluctuations as less light is scattered and movement is faster

Question 30

Limitations of Photon correlation spectroscopy

Answer 30

• Small amounts of large aggregates or dust particles can disturb the
  size determination
• Small particles can aggregate together

Question 31

Cascade impactor

Answer 31

Particles break free of the
air stream, then impact on
the collection plates

Question 32

What does a cascade impactor measure

Answer 32

• For measuring particle size of inhaled products
• Corresponds to area in the respiratory tract
• Measurement of aerodynamic diameter of sphere with same terminal velocity

Question 33

Limitations of cascade impactor

Answer 33

• Does to indaviduals having different inhalation rates of flow canot determin that all is inhaled homogenously