Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

PMY2006 > Radiochemistry > Flashcards

Radiochemistry Flashcards

1
Q

Why can alpha emission not be used un diagnostics and treatment?

A

As it is densely ionising and can therefore cause considerable biological damage.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are the most commonly used radioisotopes in biochemistry?

A

beta emitters

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Negative β decay

A

Unstable atomic nucleus with an excess of neutrons may undergo β- decay; where a neutron is converted into a proton, an electron and an electron anti-neutrino

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Positive β decay (emission)

A

Unstable atomic nuclei with excess protons undergo β+ decay (positron decay) – where a proton is converted to a neutron, positron and electron neutrino

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Why do we not use metal to protect from β emission?

A

As bombardment of metal will cause production of x-rays

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Gamma emitters/rays

A

A photon of electromagnetic radiation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Why are gamma emitters safe to use in the body to track drug movement?

A

Lots of energy in gamma radiation but it doesn’t have the particle component therefore it is safe to use in the body to track drug movement

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Each isotope emits gamma at distinct energies. What can we use this property to do?

A

We can use this property to identify isotope.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What order is spontaneous disintergration?

A

First-order process

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Disintergration

A

Rate of radioactive decay proportional to the number of atoms present (the minus sign in the equation indicates there is radioactive decay and therfore loss)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Definition of half life (t1/2) from the natural log of disintergration

A

The time required for one-half of the radioactive atoms present in the sample to decay.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What radioisotopes are used in pharmacy research?

A

Most of the isotopes used are b emitters. There are some g emitters.
The isotopes have varying half-lives which influence how they are
used during an experiment.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What two basic units of radioactivity are used today?

A

Curie, ci and Becquerel, Bq

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Why are Ci and Bq more commonly seen as (mCi)/(uCi) and (MBq)/(TBq)?

A

The Ci is a large amount of radiation, so millicuries (mCi) and microcuries (mCi) are commonly seen. Similarly, the Bq is a small amount of radiation, so megabecquerel (MBq) and terabecquerel (TBq) are commonly seen.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What 3 units of radiation are used?

A
  1. roentgen
  2. rad
  3. rem
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the unit roentgen used for?

A

A unit for measuring the amount of gamma radiation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the unit rad used for?

A

A unit for measuring the absorbed energy from radiation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is the unit rem used for?

A

A unit for measuring biological damage from radiation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is the newer SI unit for roentgen?
,

A

coulomb/kg

20
Q

What is the newer SI unit for rad?

A

gray

21
Q

What is the newer SI unit for rem?

A

seivert

22
Q

What does the gray describe?

A

The gray describes amount of energy transferred by radiation to an object. An absorbed dose of 1 gray is equal to the absorption of 1 joule of radiation energy by 1 kilogram of matter

23
Q

What is the difference between rad and gray?

A

The difference between the rad and the gray is a proportionality factor: 100 rad = 1 gray.

24
Q

What does the roetgen describe?

A

The roentgen describes a different property from energy absorbed per unit mass. The roentgen is defined as the amount of x-ray or gamma ray radiation (electromagnetic radiation) that produces 1/3 x 10-9 coulomb of electric charge in 1 cm3 of dry air at standard conditions

25
Q

What does the sievert describe?

A

The sievert is the correct unit to use when you wish to monitor the biological danger of radiation.

26
Q

What is the difference between rem and sievert?

A

The difference between the rem and the sievert is a proportionality factor: 100 rem equal 1 sievert.

27
Q

What rays cause more biological damage?

A

Beta and alpha cause more biological damage per energy absorbed than x-rays and gamma rays as damage is greater with charged particles.

28
Q

What does the number of disintergrations in a sample depend on?

A
  1. The number of radioactive atoms present (purity)
  2. Decay constant
29
Q

Will all atoms in a sample be radioactive?

A

No E.g for every 10,000 molecules, 1 will be radioactive

30
Q

What will a radioactive sample contain?

A

• radioactive atoms
• atoms resulting from decay
• non-radioactive atoms, e.g. a carrier

31
Q

What is specific activity defined as?

A

Specific activity is defined as the rate of
Disintegration per unit of sample

32
Q

What are the typical units for specific activity?

A

mCi / mmole
uCi / umole

33
Q

What does the term dpm mean in terms of counting efficiency?

A

DPM = Disintegrations per minute

34
Q

What does the term dps mean in terms of counting efficiency?

A

DPS = Disintegrations per second

35
Q

Why are dpm and dps of a sample rarely determined?

A

Beacause instruments that respond to emitted particles can only count a small fraction of them.

36
Q

How is % efficiency calculated?

A

% efficiency = (observed cpm - background cpm)
———————————————— X 100
Actual dpm

The % efficiency can be determined by counting a standard of know radio activity

37
Q

Examples of background radiation that is always present

A

Cosmic rays, Granite (in the ground), Photo-multiplier tube (PMT)

38
Q

What two procedures are widely used for detection of radioactivity?

A

• the liquid scintillation counter
• Geiger-Müller tube

39
Q

What components do samples used for liquid scintillation consist of?

A

• the radioactive material
• an organic solvent, usually aromatic
• one or more organic fluorescent substances.

40
Q

How does the scintillation counter work?

A
  1. The process begins by collision of emitted b particle with solvent
    molecule.
  2. Excess energy on the b particle is transferred to solvent, S.
  3. One b particle can transfer energy to several solvent molecules
  4. Aromatic solvents are used because of the ease of excitation.
    The excited solvent molecules return to the ground state
  5. These photons have too short a wavelength for detection, so a
    primary fluor, F1, is added to the solvent.
  6. F1* molecules are fluorescent and emit their photon at a higher wavelength. Often, this is not high enough, so a secondary fluor is used, F2,
    WONT GET ASKED THIS - TOO DIFFICULT TO ASK
41
Q

Quencing during scintillation counting

A

• It causes underestimation of activity of sample
• Variable quenching causes similar sample to be
counted differently.

42
Q

What are the two mechanisms of quenching?

A

Chemical quenching and colour quenching

43
Q

Chemical Quenching

A

Interfere with the energy transfer to the fluors, capturing the energy and releasing it as heat e.g. sodium benzoate as benzene absorbs energy

44
Q

Colour quenching

A

Unwanted dyes that can absorb in the violet-blue region. These materials act as a filter, reducing intensity of photon e.g. Amamranth - marking site with pen = causes ink to be incorperated into formulation and affect quenching

45
Q

How do we evaluate quenching?

A

• internal standard
• channels ratio
• external standardisation

46
Q

Channels ratio

A

The position of the curve gives info about the level of quenching therefore:
Counting efficiency = f (spectrum position)
If the counting efficiency is known, then the real activity (dpm) can be determined

PMY2006 (12 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions