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Pharmaceutics > Spectroscopy > Flashcards

Spectroscopy Flashcards

1
Q

What region do most drugs absorb light?

A

In the ultraviolet (UV) region of the electromagnetic spectrum (190-390 nm)

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2
Q

What region can human eyes detect?

A

Visible light

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3
Q

What does high frequency mean?

A

High energy

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4
Q

What does high wavelength mean?

A

Low energy

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5
Q

What ways can radiation interact with matter?

A

Reflection
Transparency
Absorption

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6
Q

What are the three factor is each peak in a spectrum characterised by?

A

Wavelength max- Inversely proportional to the energy of the transition
Intensity - quantity of substance in sample
Broadness of peak

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7
Q

What is the range of ultraviolet radiation?

A

100-350 nm

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8
Q

What is the range of visible radiation?

A

350-800 nm

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9
Q

What is the range for far-UV?

A

200-240

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10
Q

What is the range for near UV?

A

240-350

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11
Q

Why is it difficult to measure below 185 nm?

A

Oxygen will absorb radiation

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12
Q

UV has higher frequency and shorter wavelength than visible region what does this mean?

A

UV has higher energy

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13
Q

What does UV-Vis radiation lead to?

A

Excitation of electrons then to electronic transition due to transitions in the electronic energy levels of molecular bonds

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14
Q

When does excitation occur?

A

When energy absorbed is equal to the energy difference between binding and anti-binding orbitals

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15
Q

What is conjugated bonds?

A

When one single bond is linkage the two double bonds they said to be conjugated

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16
Q

What is conjugation result in regards to energy?

A

Less energy being needed for electronic transitions so excitation occurs with longer wavelength

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17
Q

What happens as conjugation in a molecule increases?

A

The excitation energy decreases which results in longer wavelength wavelength required for excitation

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18
Q

What are chromophores?

A

Compounds that absorb in the visible region that are coloured

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19
Q

What is the wavelength of red?

A

620-750 nm

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20
Q

What is the wavelength of orange?

A

590-620 nm

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21
Q

What is the wavelength of yellow?

A

570-590 nm

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22
Q

What is the wavelength of green?

A

495-570 nm

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23
Q

What is the wavelength of blue?

A

450-495 nm

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24
Q

What is the wavelength of violet?

A

380-450 nm

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25
Q

What region does coloured molecules absorb colour in?

A

Visible region

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26
Q

What does the Beer-Lambert law state?

A

States that the absorbance of a solution is proportional to the solutions concentration

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27
Q

What does the greater the conjugation mean in regards to absorption?

A

The higher the absorbance

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28
Q

What are concentrations expressed in, in the Beer-Lambert law?

A

mg/mL (or g/100mL)

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29
Q

Which wavelength of a molecule is chosen for analysis?

A

Wavelength of maximum absorbance

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30
Q

What is the amount of light absorbed by a solution of drug proportional to?

A

The concentration of the drug

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31
Q

What is the most common chromophores in drugs?

A

Benzene ring

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32
Q

What do bathochromic & hyperchromic shift effect in regard to symmetry?

A

Decreased symmetry

Peak goes to longer wavelength

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33
Q

What can bathochromic shift be caused by?

34
Q

What is a auxochromes?

A

Any atom or group which when added to a chromophores causes a bathochromic shift

35
Q

What is increased absorption termed?

A

Hyperchromic shift

36
Q

What is a hypochromic shift?

A

A effect that declared absorption intensity

37
Q

What is hypsochromic shift or blue shift?

A

A shift of an absorption maximum towards shorter wavelength or higher energy

38
Q

What is a bathochromic shift or red shift?

A

A shift of an absorption maximum towards longer wavelength or lower energy

39
Q

What hour auxochromes does phenylrphrine have?

A

A hydroxyl group auxochrome

40
Q

What happens in acidic conditions with phenylephrine?

A

Both hydroxyl & amino group are protonated

41
Q

What happens on basic conditions with phenylephrine?

A

Both hydroxyl & amino groups are deprotonated

42
Q

What happens when phenylrphrine is protonated?

A

Lone pair electrons on the oxygen can interact with the ring pi-system

43
Q

What happens when phenylephrine is deprotonated?

A

An extra lone pair electrons on the oxygen

44
Q

What auxochrome does procaine have?

A

Amino group

45
Q

What happens when procaine is in acidic conditions?

A

Amino groups are protonated

46
Q

What happens to procaine in basic conditions?

A

Both amino groups are deprotonated

47
Q

What happens when procaine is deprotonated?

A

Lone pair electrons in the nitrogen can interact with ring pi-system

48
Q

What happens when procaine is protonated?

A

No lone pair electrons on the nitrogen

49
Q

What do cell or curve the need to have?

A

Transparency

50
Q

What must the absorbance be less than?

51
Q

What is a diode array used for?

A

UV-Vis detection in HPLC equipment

52
Q

What is the wavelength of D2 lamp?

A

180-350 nm

53
Q

What is the wavelength of W lamp?

A

350-1000 nm

54
Q

What is a monochromator?

A

A prism or diffraction grating

55
Q

What is applications of UV-Vis spectroscopy?

A

Quantitative measurements of drugs in formulations.
Determination of some physico-chemical properties of drugs e.g. Log P, pKa.
Measuring the release of a drug form a formulation

56
Q

What are strengths of UV-Vis spectroscopy?

A

Easy to use, cheap and robust method.

Can be used as a routine method

57
Q

What are limitations of UV-Vis spectroscopy?

A

Only moderately selective

Not readily applicable to analysis of mixtures

58
Q

What is the con of UV analysis for preformulation?

A

Not tell us which molecule is absorbing the light

59
Q

What does HPLC mean?

A

High performance liquid chromatography assay

60
Q

What is the mid infrared region used for?

A

Structural confirmation

61
Q

What is the typical range of an infrared spectrum?

A

4,000-625 cm-1

62
Q

What is the spectral range of infrared spectroscopy?

A

800 nm- 1mm

63
Q

Why do we see IR spectra?

A

Chemical bond have specific vibrational energy levels which correspond to frequencies at which they may vibrate

64
Q

What must molecules be in order to be IR active?

A

Must be associated with changes in the permanent electrical dipole

65
Q

What are resonant frequencies proportional to?

A

Bond strength mass of atoms forming the bond

66
Q

What six ways can atoms in CH2 vibrate?

A 
Symmetrical
Sis spring
Wagging
Asymmetrical
Rocking 
Twisting
67
Q

What much the atoms forming a bond be in order to IR-active?

A

Atoms forming the bond must be different as partial charge is needed on each atom

68
Q

What does intensity of absorption depend on?

A

Dipole moment - relative electronegativities of the atoms involved

69
Q

Which are stronger double bonds or single bonds?

A

Double bonds

70
Q

What does reduced mass play a major role in determine in single bonds?

A

In determining v which is frequency of vibration

71
Q

Does functional groups IR absorptions change from one compound to another?

72
Q

What is the fingerprint region value?

A

Region below 1500 cm-1

73
Q

What units is wavelength expressed in?

74
Q

What are absorption bands described by?

A

Wavenumber
Signal intensity
Breadth of the peak (full width at half height)

75
Q

What is the absorption of OH?

76
Q

What is the absorption of C=O?

77
Q

What is the absorption of triple bonds?

A

2100-2200 cm-1

78
Q

What is application of IR?

A

Finger print check identity of raw materials
Preliminary check for compound identity - presence of functional groups such as carbonyl so
Used to characterise solids/semi-solids such as creams and tablets
Used to detect polymorphs of drugs

79
Q

What are polymorphs?

A

Different crystal forms of s molecule that have driftnet physical properties e.g. Solubility snd melting point, which may be important in the manufacturing process and bioavailability

80
Q

What are strengths of IR?

A

Provides complex fingerprint which is unique to the molecule/drug
Matching of a spectrum of a compound to its standard fingerprint can be carried out readily by computers

81
Q

What are limitations of IR?

A

Rarely used as quantitative technique due to complexity due to complexity of spectra
Only detects gross impurities in sample

82
Q

What is spectroscopy?

A

The study of matter and its properties by investigating light, sound or particles that are emitted, absorbed or scattered

Pharmaceutics (6 decks)

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