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3117 > powder_1 > Flashcards

powder_1 Flashcards

1
Q

properties of mesophase molecules

A
  • organic molecules
  • elongated or rectilinear molecules
  • rigid molecules
  • possess strong dipoles and easily polarisable groups
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2
Q

what are mesophase molecules classified as

A

thermotropic (solvent-free), and lyotropic (with solvent)

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3
Q

uses of mesophase molecules

A
  1. temperature sensor
  2. display- liquid crystals provide colors
  3. stabilisation of emulsions, by increasing viscosity
  4. improve solubilization drugs
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4
Q

characteristics of solids

A
  1. least amount of kinetic energy (more stable)
  2. structural rigidity, resist informative forces (short IM distance, densed and fixed)
  3. organised as crystalline or amorphous solid
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5
Q

calculated path of liquid molecules

A
  • volume with no set shape, takes shape of container
  • flow w relative ease
  • molecules move freely, unrestricted
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6
Q

calculated path of solid particles

A
  • definite mass, volume, and shape
  • molecules remain relatively immobile, oscillate about their mean positions
  • mechanically strong and incompressible
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7
Q

multi-particulate solid dosage form includes:

A
  1. powders: crystals, nanoparticles, microcapsules, microspheres
  2. granules, agglomerate
  3. pellets, spheroids, beads
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8
Q

final solid dosage form

A
  1. capsules; hard, soft
  2. tablets, caplets
  3. others: films, gums
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9
Q

why solid dosage form?

A
  1. when dry does not promote microbial growth
  2. markedly better chemical stability
  3. lower bulk volume
  4. ease of handling, added convenience
  5. flexible, single or multiple chemical components
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10
Q

what are crystals

A

crystals are ordered structures with arranged atoms, ions or molecules, forming symmetrical and repeating patterns in 3D; the basic repeating pattern is the unit cell of the structure

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11
Q

polymorphism

A

the ability of a solid to exist in more than one form or crystal structure, difference in crystal packing

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12
Q

what differs between different polymorphic forms

A

physical properties: solubility, dissolution, bioavailability, morphology thermal

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13
Q

why does solid exist in different polymorphs

A

minimise their crystal lattice energy under specific thermodynamic conditions (like temp and solute concentration)

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14
Q

properties of crystalline structures

A
  1. orderly arrangement of constituents, defined structures
  2. anisotropic, sharp x-ray diffraction patterns
  3. sharp melting points
  4. definite heat of fusion
  5. more stable
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15
Q

properties of amorphous structure

A
  1. no arrangement, irregular or undefined shapes
  2. isotropic, no well-resolved x-ray patterns
  3. melt over a range
  4. no definite heat of fusion
  5. more liable for degradation
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16
Q

preparation methods of amorphous state

A
  • milling
  • compaction
  • dehydration
  • vapor condensation
  • spray drying
  • precipitation
  • supercooling
  • freeze drying
17
Q

types of amphorous states

A
  1. amorphous
    - improve drug solubility (note 90% of new drugs under development are poorly water soluble)
  2. nanocrystalline (crystallite size of only few nanometers)
    - improve stability (but also good solubility)
18
Q

how to determine crystallinity/ polymorphism

A
  1. x-ray diffractometry (standard)
  2. melt behaviour (visual- hot stage microscopy; differential scanning calorimetry)
  3. raman spectroscopy
  4. infrared spectroscopy
  5. nuclear magnetic resonance spectroscopy
19
Q

x-ray diffraction by crystals

A

concept: planes of atoms in molecules give reflecting layers for xrays

20
Q

what is the relationship between grinding and diffraction of solids

A

milling can produce amorphous drugs, causing less diffractions, hence the x-ray diffraction pattern will have reducing peaks

21
Q

hot stage microscopy

A

visual characterisation of thermal transitions, may also have in-built sensor for calorimetric measurement

22
Q

differential scanning calorimetry

A

measure enthalpy change as a function of temperature or time, difference in the amount of heat required to increase the temperature of a sample and reference

23
Q

raman spectroscopy

A

when electromagnetic radiation is scattered, one photon of incident radiation is annihilated. at the same time, one photon of the scattered radiation is created.

24
Q

what is rayleigh scattering

A

when the energy of incident photo is equal to scattered on, the process is call rayleigh scattering

25
Q

what is raman scattering

A

when energy of incident photon is different to that of the scattered one

26
Q

advantage of raman spectroscopy

A
  1. provide distinct spectroscopic properties of a material
  2. fast measurement time
  3. able to measure from small spot size, to few microns
  4. can take measure in presence of water
27
Q

uses of raman spectroscopy

A

non-destructive, microscopic, chemical analysis applications

28
Q

how to use raman spectroscopy to tell between crystalline and amorphorous

A

crystalline: sharper narrower peaks
amorphous: rounder broader shorter peaks

3117 (15 decks)

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