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3.23 > Lecture 3: Challenges of CV disease - Formulation and practice > Flashcards

Lecture 3: Challenges of CV disease - Formulation and practice Flashcards

1
Q

What are the strengths of UV/Vis spectroscopy in pharmacy? (3)

A
  • Easy to use, cheap and robust
  • Quantitative measurements of drugs in formulations
  • Routine methods to asses physiochemical properties of drug
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2
Q

What are the limitations of UV/Vis spectroscopy in pharmacy? (4)

A
  • Only moderately selective
  • Drugs need to have a chromophore
  • Not readily applicable to analysis of mixtures
  • Lack specificity
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3
Q

What is spectroscopy?

A

The study of molecular structure and dynamics through the absorption, emission and scattering of light

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4
Q

What is light?

A

An electromagnetic field characterised by a frequency f, velocity v and wavelength

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5
Q

What is the relationship of light

A

f = v/ wavelength

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6
Q

What colour does the human eye see when light is transmitted?

A

The colour complementary to that which is absorbed

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7
Q

How is transmittance calculated?

A

T = lt/l0

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8
Q

How is absorbance calculated?

A

A = log10 l0/lt

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9
Q

What is the beer lambert law?

A

A=abc

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10
Q

What is a?

A

Absorptivity

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11
Q

What are the two forms of absorptivity?

A

Molar and specific

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12
Q

What is b?

A

Pathlength

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13
Q

What is c?

A

Concentration of analyte / chromophore in solution

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14
Q

What is quantitative analysis?

A

Single absorbing substance - two ways of determining the concentration of an unknown solution

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15
Q

What are the two methods of quantitive analysis?

A
  1. Use of a literature A (1%, 1cm) or E values
  2. Use of a calibration line/ curve
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16
Q

When is a literature value used?

A
  • When a pure standard is not available
  • Used in many blood pressure assays
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17
Q

How do you calculate absorbance and wavelength scales of the spectrophotometer?

A

y = mx + c

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18
Q

What is y?

A

Absorbance

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19
Q

What is m?

A

Slope of the line

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20
Q

What is x?

A

Concentration (how far along)

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21
Q

What is c?

A

Intercept
- Should be zero or negligible

22
Q

How is the validity of Beers Law checked?

A
  • Use calibration line to determine concentration of the sample either manually or by linear regression (equation)
  • For linear regression, rearange the equation to solve for x (ie unknown concentration)
  • Need to use pure standard, prepare standard solutions
23
Q

What absorbing components can pharmaceutical samples contain?

A
  • Active ingredients
  • Excipients: preservatives/ anti- oxidants, binders, disintegrants, colouring/ flavouring agents
  • Impurities from synthesis: starting materials, byproducts, intermediate products
24
Q

What are the units of ε ?

A

liters/mole cm

25
Q

what is ε?

A

Molar absorptivity

26
Q

What can ε be known as?

A
  • Molar absorption coefficient
  • Extinction coefficient
27
Q

What is A (1%, 1cm)

A

The absorbance of a 1g/100ml solution in a 1cm cell

28
Q

How can drug release be monitored?

A

UV visable spectroscopy

29
Q

What is esmolol?

A

Beta blocker

30
Q

How does UV spectroscopuy lack specificity?

A

On an abosrbance graph the shape of the graph for different drugs may be the same so cant differentiate between different drugs.

31
Q

What range does UV vis specrometry cover?

A

Ultraviolet / visable range

32
Q

What is used to calculate how much energy a specific type of EM radiation carries?

A

E=hc/ wavelength

33
Q

How does a spectrophotometer work?

A

Select a wavelength that we know will excite electrons to go to a higher level.
Spectrophotometer has a light source that is split into the different components of the light.
A selector selects the correct wavelength to be shown on the sample
The spectrophotometer detects ho much light is being shone on the detector

34
Q

Where does the UV spectra start?

A

200nm

35
Q

Where does the visable spectra start?

A

700nm

36
Q

What is a chromophore?

A

A chemical structure that loves to absorb specific wavelengths of light

37
Q

Name a good chromophore

A

Benzene rings are good chromophores because of the type of orbitals it has. The electrons can be excited to higher orbitals.

38
Q

What is transmittance?

A

The transmitted light

39
Q

what is Io?

A

Incidence light - the light shone onto the sample, it has a certain length. Some of this light is absorbed by the compoundd present in the cuvette, the compound in the solution has a chromophore and can absorb some of the light. The amount of transmited light is less than what is being shined into the sample.

40
Q

What is It

A

The amount of light that comes out at the end of the cuvette

41
Q

What is Io?

A

How much light is put into the cuvette

42
Q

What does an increase in chromophore mean?

A

The concentration of the compound is increased so less light is transmitted from the cuvette

43
Q

What effect does making the cuvette wider have?

A

More chromophore in the cuvette, so less light comes out the other end as more is absorbed by the chromophore in solution

44
Q

What is the pathlength?

A

Length the light travels in the cuvette.

45
Q

How does a high concnetration of chromophore affect the transmittance value?

A

Transmittance value becomes small

46
Q

What is the Beer lamberts law?

A

A simple version of calculating the absorbance

47
Q

What does the beer lambarts law state?

A

Absorbance is porportional to pathlength and concnetration

48
Q

What is beer lamberts law used to calculate?

A

How much drug is in solution

49
Q

What is another name for molar absorptivity?

A

Molar exctinction coefficiant

50
Q

Why is y=mc+c a straight line?

A

Absorptivity is porportional to concentration

3.23 (26 decks)

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