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HYPERTENSION > Powders > Flashcards

Powders Flashcards

1
Q

What is a mono-disperesed powder ?

A

A powder in which EVERY particle is the same size. This means that the population can be identified by a SINGLE PARAMETER.

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2
Q

TRUE OR FALSE

The peak in a ‘positively skewed’ histogram lies on the lower value side.

A

TRUE

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3
Q

The tail in a negatively skewed histrogram faces the higher values.

A

FALSE - on a negatively skewed histrogram the tail faces the lower values.

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4
Q

What value is extractable from a histogram distribution ?

A

The mode

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5
Q

TRUE OR FALSE

A bimodal size distribution has two medians

A

FALSE - It has two local maxinums.

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6
Q

What data is extractable from a cumulative frequency graph ?

A

The median and the interquartile range.

The interquartile range describes how broad the distribution is within a dataset.

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7
Q

What does sieve analysis determine ?

A

Sieve analysis is used to determine the distribution of the particle diameters.
Every level has holes of different diameter and therefore the amount of particles in each level signify their diameter.

This data is best represented in a cumulative frequency graph.

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8
Q

What is the minimum particle diameter that a mechanical sieve can measure up to ?

A

45μm

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9
Q

What types of sieving are there ?

A
  • Air jet sieving
  • Mechanical sieving
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10
Q

What are the pros and cons of air jet sieving ?

A

Pros:
* More accurate
* More reproducable results

Cons:
* Takes longer time
* Air jet sieving requires a partial vacuum

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11
Q

TRUE OR FALSE

Optical microscopy is a three dimensional assessment method

A

FALSE

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12
Q

Light microscope max measure

A

10μm

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13
Q

Electron miscroscope maxinum measure

A

100μm

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14
Q

What are microscopes used for on particles ?

A

To measure their size (diameter).

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15
Q

What are the different types of diameters ?

A
  • Projected perimeter diameter
  • Projected area diameter
  • Martins diameter
  • Feret’s diameter
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16
Q

How is the projected area diameter measured ?

A

There is an equal amount of particle outside the diameter ring as there is inside.

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17
Q

How is the projected perimeter diameter measured?

A

The diameter ring encapsulates the WHOLE particle

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18
Q

How is Martins diameter measured?

A

Draw a line down the middle of the particle so that there is an EQUAL amount of particle on either side.

19
Q

Disadvantage of wet granulation

A

Not suitable for moisture-sensetive drugs

20
Q

Electrical stream sensing zone

A

The measuring of the particle volume diameter.

The particles are placed in an electrolyte solution. One-by-one they pass through between two electrodes. The electrodes pick up the increase in resistance from the particle.

21
Q

ESSZ issues

A

Difficult to ensure that particles pass one-by-one.
* Electrode gap TOO LARGE = multiple particles fit through.
* Electrode gap TOO SMALL = particles are blocked from passing through.

The electrolyte solution should be SATURATED to avoid the particles dissolving.

IDEALLY you want single particle passage for the highest accuracy.

22
Q

ESSZ benefits

A
  • Quick and easy
  • particle size aplication 0.1-1000μm
23
Q

Laser light scattering

A

A laser is applied to a suspension of particles in which the level of diffraction correlates to a certain diameter range.

The smaller the particle = Higher level of diffraction.
Two types:
* Large-light particle analysers [1-1000μm]
* Photon correlation [10nm-1μm]

24
Q

Laser light scattering issue

A

It has to be a helium-neon laser

25
Q

TRUE OR FLASE

Large particle analysers can measure up to 10nm

A

FALSE - Photon correlation 10nm-1μm

large particle = 1-1000μm

26
Q

LLS benefits

A
  • Rapid
  • Reliable results
  • Can produce a particle size distribution graph.
27
Q

TRUE OR FALSE

Adhesive powders DO NOT flow well

A

FALSE - Cohesive powders do not flow well.

28
Q

Adhesion

A

The attraction between a material and a DIFFERENT material.

29
Q

Cohesion

A

The attraction betweena material and an IDENTICAL material.

30
Q

General rule of cohesion and powders

A

The less cohesive a powder is the better it will flow.

31
Q

UNAVOIDABLE INTERPARTICULAR FORCE

A

van der Waals force

higher surface area = more van der waals

32
Q

Interparticular forces

A
  • Van der waal force
  • Electrostatic charging
  • Surface tension forces between absorbed liquid
33
Q

TRUE OR FALSE

LARGE particles flow better than small particles

A

TRUE

34
Q

TRUE OR FALSE

Round particles flow better than needles (or other complex shapes)

A

TRUE

35
Q

Angle of repose

A

By pouring a powder onto a plate you can measure the angle between the flat surface and the peak of the heap.

HIGHER ANGLE = HIGHER LEVEL OF COHESION

>50 degrees = poor flow

36
Q

Angle of inclination

A
37
Q

Coefficient of internal friction

A

μ=tanθ
* μ= coefficient of internal friction
* θ = angle of repose

38
Q

Bulk density measurement

A
  1. Measure the density of the initial powder.
  2. Pour powder into tube.
  3. Turn on machine and let it consolidate the tapping the tube.
  4. Measure density of the powder after tapping.

Use hausner ratio to measure flowability

39
Q

Hausner ratio

A

An equation that allows you to determine the flowability of a powder.

Df/Do
* Df = Final bulk density
* Do = Initial powder density

40
Q

TRUE OR FALSE

A hopper determines the singular flow rate of the bulk powder

A

FALSE - Different zones form in the hopper of which have different flow rates.

41
Q

Hausner ratio standards

A

<1.2 = good flow
>1.6 = poor flow

42
Q

Hopper issues

A

‘Ratholing’ or ‘bridging’ is very common

43
Q

Hopper benefits

A

They display the efficiency of and reproducability of flow.

HYPERTENSION (12 decks)

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