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PHA6124 LEC Manufacturing Pharmacy > Mixing > Flashcards

Mixing Flashcards

1
Q

unit operation that aims to treat two or more components, initially in an unmixed or partially mixed state

A

mixing

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2
Q

done so that each unit (particle, molecule, etc.) of the components lies as nearly as possible in contact with a unit of each of the other components

A

mixing

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3
Q

ideal situation when each particle lay adjacent to a particle of the other component

A

perfect mix

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4
Q

probability of selecting a particular type of particle is the same at all positions and is equal to the proportion of such particles in the total mix

A

random mix

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5
Q

[TRUE OR FALSE] In a perfect mix, a particular particle is the same at all positions and is equal to the proportion of such particles in the total mix

A

FALSE - random mix

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6
Q

Importance of Mixing

A
  1. Ensure even distribution of active components
  2. Ensure even appearance
  3. Ensure that the dosage form releases the drug at the correct site at the desired rate
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7
Q

Types of mixtures

A
  1. Positive
  2. Negative
  3. Neutral
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8
Q

formed from gases or miscible liquids

A

positive mixtures

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9
Q

mix spontaneously and irreversibly by diffusion

A

positive mixtures

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10
Q

Positive mixtures mix spontaneously and irreversibly by diffusion, and tend to approach a _______________

A

perfect mix

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11
Q

no energy input needed

A

positive mixtures

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12
Q

materials that use this type of mixing present no problems during manufacture

A

positive mixtures

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13
Q

components tend to separate out

A

negative mixtures

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14
Q

continuous energy input is required to keep the components adequately dispersed

A

negative mixtures

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15
Q

type of mixture that is more difficult to form and maintain

A

negative mixtures

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16
Q

require a higher degree of mixing efficiency

A

negative mixtures

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17
Q

static behavior

A

neutral mixtures

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18
Q

components tend to mix spontaneously or segregate spontaneously once work has been input to mix them

A

neutral mixtures

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19
Q

mixed powders, pastes, ointments

A

neutral mixtures

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20
Q

Mathematical Treatment of Mixing Process

A
  1. STD
  2. % coefficient of variation
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21
Q

Mechanism of mixing and demixing of powders (P-CSD)

A

convection mixing, shear mixing, and diffusion mixing

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22
Q

Mechanism of mixing and demixing of liquids (L-BTM)

A

bulk transport, turbulent mixing, molecular diffusion

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23
Q

powder segregation

A

demixing

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24
Q

transfer of relatively large group of particles from one part of the powder bed to another

A

convection mixing

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25
Q

[TRUE OR FALSE] In convection mixing, transfer might occur when a mixer blade or paddle moves through the mix

A

TRUE

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26
Q

mainly contributes to the macroscopic mixing of powder mixtures

A

convection mixing

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27
Q

produce large degree of mixing fairly quickly

A

convection mixing

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28
Q

[TRUE OR FALSE] convection mixing occurs within the same group of particles, thus an extended mixing time is required

A

FALSE - does not occur in the same group of particles

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29
Q

occurs when a layer of material moves or flows over another layer

A

shear mixing

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30
Q

might be due to the removal of mass by convective mixing, creating an unstable shear/slip plane

A

shear mixing

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31
Q

cause the powder bed to collapse

A

unstable shear/slip plane

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32
Q

occurs in high shear mixers or tumbling mixers where the action of the mixer induces velocity gradients within the powder bed

A

shear mixing

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33
Q

movement of indiv particles through voids

A

diffusive mixing

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34
Q

voids are created by ___________

A

gravity

35
Q

potential to produce random mix, resulting in a low rate of mixing

A

diffusive mixing

36
Q

analogous to convective mixing of powders

A

bulk transport

37
Q

movement of a relatively large amount of material from one position in the mixer to another (e.g., due to mixer paddle)

A

bulk transport

38
Q

from haphazard movement of molecules when forced to move in a turbulent manner

A

turbulent mixing

39
Q

in turbulent mixing, constant changes in speed and direction means that induced turbulence is _______________________ mechanism for mixing

A

highly effective mechanism

40
Q

analogous to diffusive mixing in powder

A

molecular diffusion

41
Q

occur with miscible fluids wherever a conc gradient exits; eventually produce well-mixed product

A

molecular diffusion

42
Q

demixing; opposite effect of mixing

A

powder segregation

43
Q

components tend to separate out

A

powder segregation

44
Q

cause an increase in content variation in samples taken from the mix

A

powder segregation

45
Q

may cause a batch to fail a uniformity of content test

A

powder segregation

46
Q

particle size effects, particle density effects, particle shape effects

A

powder segregation

47
Q

occurs when powder mix, owing to interactions and cohesive/adhesive forces between constituents

A

ordered mixing

48
Q

most likely to occur when smaller particle exist due to their high specific surface area

A

Ordered Mixing

49
Q

[TRUE OR FALSE] Smaller particles have higher specific surface area, so the attractive forces holding the particles to the adsorption site are more likely to be greater than the gravitational forces trying to separate the components

A

TRUE

50
Q

ordered mixes can reduce or prevent segregation, it occurs if:

A
  1. carrier particles vary in size
  2. there is a competition for the active sites on the carrier particle
  3. there are insufficient carrier particles
51
Q

[TRUE OR FALSE] Mixers should be earthed to dissipate the static charge and the process should be carried out at a RH < approx. 40%

A

FALSE - >approx. 40%

52
Q

Powder mixing equipment

A
  1. Tumbling mixers
  2. High Speed mixer-granulators
  3. Fluidized bed mixers
  4. Agitated mixers
53
Q

commonly used for the mixing/blending of granules or free flowing powders but poor for cohesive or poorly flowing powders

A

tumbling mixers

54
Q

common use is in blending lubricants, glidants, or external disintegrant with granules prior to tableting

A

tumbling mixers

55
Q

can also be used to produce ordered mixes

A

tumbling mixers

56
Q

common to use IBCs both as the mixer bowl and to either feed the hopper of a tablet or capsule machine or as the hopper itself

A

tumbling mixers

57
Q

can both mix and granulate a product, removing the need to transfer the product between pieces of equipment and reducing the opportunity for segregation

A

high speed mixer-granulators

58
Q

drying of granules or coating of multiparticulates

A

fluidized bed mixers

59
Q

mix powders prior to granulation in the same bowl

A

fluidized bed mixers

60
Q

depends on the motion of a blade or paddle through the product, and hence the main mixing mechanism is convection

A

agitator mixers

61
Q

mixing is achieved by the rotation of helical blades in a hemispherical trough.

A

agitator mixers

62
Q

dead spots are difficult to eliminate in this type of mixer and the shearing action caused by the movement of the blades may be insufficient to break up drug aggregates

A

agitator mixers

63
Q

mixer poorly mix flowing material and is less likely to cause segregation than a tumbling mixer

A

agitator mixers

64
Q

[TRUE OR FALSE] Mobile liquids with low viscosity are not easily mixed with each other

A

FALSE - easily mixed

65
Q

[TRUE OR FALSE] Solid particles are readily suspended in mobile liquids, although particles settle slowly when mixing is discontinued

A

FALSE - settle rapidly

66
Q

Viscous liquids are more difficult to stir and mix but they reduce the ____________________ of suspended particles

A

sedimentation rate

67
Q

equipments used for the mixing of miscible liquids and susps

A

propeller mixer, turbine mixers, in lin mixers

68
Q

common arrangement for medium scale fluid mixing, which may be clamped to the edge of a vessel

A

propeller mixers

69
Q

[TRUE OR FALSE] Vortex forms when the centrifugal force imparted to the liquid by the propeller blades causes it to back up around the sides of the vessel and create a depression at the shaft.

A

TRUE

70
Q

ratio of the diameter of a propeller stirrer to that of the vessel

A

1:10 - 1:20

71
Q

propeller mixers operate at what speed

A

1-20 rps

72
Q

used for more viscous fluids

A

turbine mixers

73
Q

absence of an axial component, but a different head with the perforations pointing upwards can be fitted if this is desired

A

drawback of turbine mixers

74
Q

as the liquids is forced through the small orifices of the diffuser rings at high velocity large shear forces are produced

A

turbine mixers

75
Q

will not cope with liquids of very high viscosity, as the material will not be drawn into the mixer head

A

turbine mixers

76
Q

need continuous mixing process

A

inline mixers

77
Q

as an alternative to mixing fluids in batches in vessels, mobile miscible components may be fed through an inline mixer designed to create turbulence in a flowing fluid stream

A

inline mixers

78
Q

mixers used in mixing semisolids

A

planetary mixers, sigma blade mixer

79
Q

[TRUE OR FALSE] Semisolids will not flow easily as compared to powders and liquids

A

TRUE

80
Q

Commonly found in domestic kitchen and larger machines which operate on the same principle are used in industry

A

planetary mixers

81
Q

Used to mix powders, particularly if a wet mass granulation is required

A

planetary mixers

82
Q

Robust mixer that will deal with stiff pastes and ointments and depends for its action on the close intermeshing of the 2 blades

A

sigma blade mixer

83
Q

very difficult using primary mixers to completely disperse powder particles in a semisolid base so that they are invisible to the eye

A

sigma blade mixer

84
Q

mix is usually subjected to the further action of roller mill or colloid mill, so as to rub out these particles by the intense shear generated by rollers or cones set with very small clearance between them

A

sigma blade mixer

PHA6124 LEC Manufacturing Pharmacy (4 decks)

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