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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
What region does coloured molecules absorb colour in?
Visible region
26
What does the Beer-Lambert law state?
States that the absorbance of a solution is proportional to the solutions concentration
27
What does the greater the conjugation mean in regards to absorption?
The higher the absorbance
28
What are concentrations expressed in, in the Beer-Lambert law?
mg/mL (or g/100mL)
29
Which wavelength of a molecule is chosen for analysis?
Wavelength of maximum absorbance
30
What is the amount of light absorbed by a solution of drug proportional to?
The concentration of the drug
31
What is the most common chromophores in drugs?
Benzene ring
32
What do bathochromic & hyperchromic shift effect in regard to symmetry?
Decreased symmetry | Peak goes to longer wavelength
33
What can bathochromic shift be caused by?
Solvent
34
What is a auxochromes?
Any atom or group which when added to a chromophores causes a bathochromic shift
35
What is increased absorption termed?
Hyperchromic shift
36
What is a hypochromic shift?
A effect that declared absorption intensity
37
What is hypsochromic shift or blue shift?
A shift of an absorption maximum towards shorter wavelength or higher energy
38
What is a bathochromic shift or red shift?
A shift of an absorption maximum towards longer wavelength or lower energy
39
What hour auxochromes does phenylrphrine have?
A hydroxyl group auxochrome
40
What happens in acidic conditions with phenylephrine?
Both hydroxyl & amino group are protonated
41
What happens on basic conditions with phenylephrine?
Both hydroxyl & amino groups are deprotonated
42
What happens when phenylrphrine is protonated?
Lone pair electrons on the oxygen can interact with the ring pi-system
43
What happens when phenylephrine is deprotonated?
An extra lone pair electrons on the oxygen
44
What auxochrome does procaine have?
Amino group
45
What happens when procaine is in acidic conditions?
Amino groups are protonated
46
What happens to procaine in basic conditions?
Both amino groups are deprotonated
47
What happens when procaine is deprotonated?
Lone pair electrons in the nitrogen can interact with ring pi-system
48
What happens when procaine is protonated?
No lone pair electrons on the nitrogen
49
What do cell or curve the need to have?
Transparency
50
What must the absorbance be less than?
2
51
What is a diode array used for?
UV-Vis detection in HPLC equipment
52
What is the wavelength of D2 lamp?
180-350 nm
53
What is the wavelength of W lamp?
350-1000 nm
54
What is a monochromator?
A prism or diffraction grating
55
What is applications of UV-Vis spectroscopy?
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
What are strengths of UV-Vis spectroscopy?
Easy to use, cheap and robust method. | Can be used as a routine method
57
What are limitations of UV-Vis spectroscopy?
Only moderately selective | Not readily applicable to analysis of mixtures
58
What is the con of UV analysis for preformulation?
Not tell us which molecule is absorbing the light
59
What does HPLC mean?
High performance liquid chromatography assay
60
What is the mid infrared region used for?
Structural confirmation
61
What is the typical range of an infrared spectrum?
4,000-625 cm-1
62
What is the spectral range of infrared spectroscopy?
800 nm- 1mm
63
Why do we see IR spectra?
Chemical bond have specific vibrational energy levels which correspond to frequencies at which they may vibrate
64
What must molecules be in order to be IR active?
Must be associated with changes in the permanent electrical dipole
65
What are resonant frequencies proportional to?
Bond strength mass of atoms forming the bond
66
What six ways can atoms in CH2 vibrate?
``` Symmetrical Sis spring Wagging Asymmetrical Rocking Twisting ```
67
What much the atoms forming a bond be in order to IR-active?
Atoms forming the bond must be different as partial charge is needed on each atom
68
What does intensity of absorption depend on?
Dipole moment - relative electronegativities of the atoms involved
69
Which are stronger double bonds or single bonds?
Double bonds
70
What does reduced mass play a major role in determine in single bonds?
In determining v which is frequency of vibration
71
Does functional groups IR absorptions change from one compound to another?
No
72
What is the fingerprint region value?
Region below 1500 cm-1
73
What units is wavelength expressed in?
Cm-1
74
What are absorption bands described by?
Wavenumber Signal intensity Breadth of the peak (full width at half height)
75
What is the absorption of OH?
3300cm-1
76
What is the absorption of C=O?
1700 cm-1
77
What is the absorption of triple bonds?
2100-2200 cm-1
78
What is application of IR?
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
What are polymorphs?
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
What are strengths of IR?
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
What are limitations of IR?
Rarely used as quantitative technique due to complexity due to complexity of spectra Only detects gross impurities in sample
82
What is spectroscopy?
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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