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Management of GI and Endocrine Conditions > Lecture 15 - Analytical Methods > Flashcards

Lecture 15 - Analytical Methods Flashcards

1
Q

What does pharmaceutical analysis do?

A

determines the quality of drug products via analytical chemistry

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2
Q

What are the variety of analytical techniques?

A

spectroscopic, chromatographic and diffraction

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3
Q

What does each technique play a role in?

A

determining the quality of the pharmaceutical product and excipients

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4
Q

How to analyse pharmaceutical products?

A

UV/Vis spectroscopy

high pressure liquid chromatography

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5
Q

How to analyse the solid product?

A

Infrared spectroscopy

xray diffraction

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6
Q

UV/Vis spectrum?

A

radiate a UV light source through the sample, molecules absorb different wavelengths of radiation and the light which isn’t absorbed reaches a detector which allows us to plot absorbance vs wavelength

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7
Q

What is the lowest energy transitions?

A

rotational

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8
Q

What radiation induces transitions within rotational energy levels?

A

microwave raidation

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9
Q

What induces transitions within the vibrational energy levels?

A

Infrared radiation

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10
Q

What induces transitions within the electronic energy levels?

A

UV/Vis wavelengths

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11
Q

What are transitions?

A

electrons jumping from low energy states to high energy states

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12
Q

What else is related to electronic?

A

fluorescence and phosphorescence - related to changes in electronic structure

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13
Q

At room temp, what states are most molecules in?

A

ground vibrational and electronic states

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14
Q

How do molecules absorb radiation?

A

if polychromatic light of the correct wavelength interacts with the molecules

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15
Q

What happens to certain types of electrons?

A

they will be excited to higher energy states (electron transition)

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16
Q

What is the excitation accompanied by?

A

invariably accompanied by an increase in the energy levels of rotational and vibrational states

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17
Q

Where can transitions occur between?

A

between low electron energy levels to higher electron energy levels

can also get transitions from within the rotational energy levels, e.g. from first rotational level in the lower state to first in the higher state

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18
Q

What type of electronic transitions do not follow the specific pattern?

A

one that goes from the highest rotational energy level on the lower level, to the first rotational energy level on the higher level

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19
Q

How does a conventional spectrophotometer work?

A

polychromatic light source hits a diffraction grate, which splits the light up into its individual wavelengths (spectrum)

the exit slit then selects particular wavelengths of light that have come off the diffraction grate and allow it to pass through our sample

the sample absorbs some of the light and what isnt absorbed passes through to the PMT, which amplifies the signal

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20
Q

What is the PMT?

A

photomultiplier tube

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21
Q

How does a PDA spectrophotometer work?

A

polychromatic light passes through the whoe sample and the light is absorbed by the molecules contained

the light which is not absorbed passes through the diffraction grating, which seperates out the polychromatic light into a spectra

we then have a photodiode array which is a series of photosensitive diodes and each wavelength of light hits a specific diode

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22
Q

Benefits of PDA spectrophotometer?

A

increases the speed of analysis and allows us to asses the effect of interfering peaks more accurately

they are more expensive and have few moving components

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23
Q

Disadvantages of conventional spectrophotometer?

A

require more maintenance because they have many moving components

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24
Q

What is beer’s law?

A

the intensity of a beam of parallel monochromatic light decreases exponentially with the number of absorbing molecules

absorbance is proportional to the concentration

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25
Q

What does lambert’s law state?

A

absorbance is proportional to path length

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26
Q

What is the beer lambert law?

A

A = A(1%, 1 cm).b.c

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27
Q

what is the A11 value?

A

the specific absorbance or specific absorbance coefficient

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28
Q

What is c in BL?

A

concentration in g/100ml (%w/v)

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29
Q

what is A in BL?

A

absorbance

30
Q

what is b in BL?

A

path length in cm

31
Q

What is A(1%, 1 cm)?

A

the absorbance of a 1g/100ml solution in a 1cm cell at a specific wavelength

32
Q

What does light scattering in a sample cause?

A

absorbance > true, we overestimate the absorbance

33
Q

What is light scattering?

A

the light will hit small particles in the sample, and will be scattered, hitting internal surfaces of the UV spectrophotometer

the light is no longer making it to the detector and the detector things its been lost

34
Q

How can we prevent light scattering?

A

by filtering our sample

35
Q

What can the beer lambert law quantify?

A

the amount of sample present or the amount of analyte in a sample

36
Q

What does ionisation cause?

A

structural changes that can cause changes in the electronic system, this changes the UV spectra

it causes a shift in the absorption spectra

37
Q

What is an issue with UV/Vis?

A

its lack of specificity

it does not allow us to discriminate between closely related structures

38
Q

What is absorbance?

A

additive, so total absorbance may be from more than one compound absorbing at that particular wavelength

39
Q

What is chromatography?

A

a separation technique

40
Q

How does chromatography work?

A

we spot our mixture of component on the TLC plate of an appropriate solvent, and immerse this within the tank

the bottom of the TLC plate sits within the mobile phase and through capillary action it would be drawn up the plate

as the mobile phase migrates up the plate, it drags along the components at different rates

41
Q

What affects the rate the components are separated at?

A

the interaction with the stationary phase

if it interacts more strongly with the stationary phase, it will be more retained

42
Q

What is column chromatograpy?

A

mixture is applied to the column in solvent

applying a flow of eluate to this compound allows the components to start to migrate through the column

43
Q

what is the stationary phase typically in chromatography?

A

silica gel

44
Q

What does column chromatography allow us to get?

A

a chromatogram, plotting response against time

45
Q

What does the chromatogram allow?

A

to quantify the use of the components within the mixture

46
Q

What is the frequency of use of tablets and capsules?

A 
tabs = 46%
capsules = 13%
47
Q

What is the frequency of use of oral liquids and injections?

A

oral liquids = 16%

injections = 15%

48
Q

What are the physiochemical properties of solid dosage forms correlated to?

A

the crystal structure of the raw materials

49
Q

What does the final product affect?

A

the stability and the bioavailability

50
Q

What is an IR spectrum?

A

graph of absorbance or % transmission against wavelength or wavenumber

%T = It/Io and A = log Io/It

51
Q

What is the wavenumber?

A

number of waves in 1cm

units are cm-1

52
Q

What is energy of IR proportional to?

A

E = 1/wavelength

53
Q

IR has less energy than..?

A

UV/visible light

54
Q

What does absorption of IR cause transitions in?

A

vibrational and rotational energy levels

55
Q

For a compound to be active in IR what must absorption cause?

A

a change in dipole moment of the molecule

56
Q

Stretching vibrations?

A

symmetric and asymmetric

result in a shift in the dipole of the molecule

57
Q

Bending vibrations?

A

in plane rocking

in plane scissoring

out of plane wagging

out of plane twisting

58
Q

What do bending vibrations result in?

A

A change of the dipole moment of the molecule

59
Q

What is a strength of IR?

A

The specificity

60
Q

What is the lower region of the IR spectrum?

A

the finger print region

specific to each individual molecule

61
Q

What can we use the finger print region for?

A

to determine the exact structure of our analyte

62
Q

What is polymorphism?

A

the ability of a compound to crystallise in more than one 3D packing arrangement

63
Q

What do different polymorphs have?

A

distinct IR patterns if we look at the finger print regions

64
Q

What can polymorphism cause?

A

different dissolution and bioavailability

65
Q

What is the unit cell of a molecule?

A

the smallest repeating unit

66
Q

What is Bragg’s law?

A

nλ = 2dsinθ

67
Q

What do crystalline forms show?

A

diffraction

68
Q

What do amorphous forms show?

A

they do not diffract

69
Q

What types of X ray diffraction are available?

A

powder or single crystal X ray diffraction

70
Q

What does powder X ray diffraction give us?

A

a similar finger print pattern as IR

71
Q

what does single crystal X ray diffraction give?

A

absolute structure of particular analyte

Management of GI and Endocrine Conditions (24 decks)

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