Lecture 3: Challenges of CV disease - Formulation and practice

Question 1

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

Answer 1

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

Question 2

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

Answer 2

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

Question 3

What is spectroscopy?

Answer 3

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

Question 4

What is light?

Answer 4

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

Question 5

What is the relationship of light

Answer 5

f = v/ wavelength

Question 6

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

Answer 6

The colour complementary to that which is absorbed

Question 7

How is transmittance calculated?

Answer 7

T = lt/l0

Question 8

How is absorbance calculated?

Answer 8

A = log10 l0/lt

Question 9

What is the beer lambert law?

Answer 9

A=abc

Question 10

What is a?

Answer 10

Absorptivity

Question 11

What are the two forms of absorptivity?

Answer 11

Molar and specific

Question 12

What is b?

Answer 12

Pathlength

Question 13

What is c?

Answer 13

Concentration of analyte / chromophore in solution

Question 14

What is quantitative analysis?

Answer 14

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

Question 15

What are the two methods of quantitive analysis?

Answer 15

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

Question 16

When is a literature value used?

Answer 16

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

Question 17

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

Answer 17

y = mx + c

Question 18

What is y?

Answer 18

Absorbance

Question 19

What is m?

Answer 19

Slope of the line

Question 20

What is x?

Answer 20

Concentration (how far along)

Question 21

What is c?

Answer 21

Intercept
- Should be zero or negligible

Question 22

How is the validity of Beers Law checked?

Answer 22

• 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

Question 23

What absorbing components can pharmaceutical samples contain?

Answer 23

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

Question 24

What are the units of ε ?

Answer 24

liters/mole cm

Question 25

what is ε?

Answer 25

Molar absorptivity

Question 26

What can ε be known as?

Answer 26

- Molar absorption coefficient - Extinction coefficient

Question 27

What is A (1%, 1cm)

Answer 27

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

Question 28

How can drug release be monitored?

Answer 28

UV visable spectroscopy

Question 29

What is esmolol?

Answer 29

Beta blocker

Question 30

How does UV spectroscopuy lack specificity?

Answer 30

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

Question 31

What range does UV vis specrometry cover?

Answer 31

Ultraviolet / visable range

Question 32

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

Answer 32

E=hc/ wavelength

Question 33

How does a spectrophotometer work?

Answer 33

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

Question 34

Where does the UV spectra start?

Answer 34

200nm

Question 35

Where does the visable spectra start?

Answer 35

700nm

Question 36

What is a chromophore?

Answer 36

A chemical structure that loves to absorb specific wavelengths of light

Question 37

Name a good chromophore

Answer 37

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

Question 38

What is transmittance?

Answer 38

The transmitted light

Question 39

what is Io?

Answer 39

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.

Question 40

What is It

Answer 40

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

Question 41

What is Io?

Answer 41

How much light is put into the cuvette

Question 42

What does an increase in chromophore mean?

Answer 42

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

Question 43

What effect does making the cuvette wider have?

Answer 43

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

Question 44

What is the pathlength?

Answer 44

Length the light travels in the cuvette.

Question 45

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

Answer 45

Transmittance value becomes small

Question 46

What is the Beer lamberts law?

Answer 46

A simple version of calculating the absorbance

Question 47

What does the beer lambarts law state?

Answer 47

Absorbance is porportional to pathlength and concnetration

Question 48

What is beer lamberts law used to calculate?

Answer 48

How much drug is in solution

Question 49

What is another name for molar absorptivity?

Answer 49

Molar exctinction coefficiant

Question 50

Why is y=mc+c a straight line?

Answer 50

Absorptivity is porportional to concentration