atomic absorption

Question 1

explain the components of a flame photometer and its mechanism.

Answer 1

• sample, nebuliser, burner, hollow cathode lamp, monochromator, PMT, digital display

Question 2

explain what background correction is and why its used

Question 3

briefly explain the light source used in atomic absorption

Answer 3

1. hollow cathode lamp
2. cathode is made of sample being analysed
3. low pressure Ar or Ne in lamp
4. high energy e- emitted by cathode
5. gas ionizes from e-
6. metal atoms excited by collisions with e- and ions

Question 4

what is background correction and how does it work

Answer 4

use a deuterium lamp and a rotating mirror

some samples can bond with other gases in the lamp which will cause a broad spectrum when the atom spectrum should be quite fine.

the deuterium lamp should only detect the background detection. whilst the cathode will measure the atom band AND the background.

so you subtract the background from the cathode lamp reading.

Question 5

what are the advantages to the graphite furnace

Answer 5

1. safer than FAAS because you don’t have to use volatile gases
2. don’t need a nebuliser
3. atoms present in the atom cell for a relatively long time
4. only small amounts of sample material required
   5.can use solid samples
5. heated electrically so removes flame interferences

Question 6

disadvantages of AA

Answer 6

• only determines 1 metal at a time
• need to change lamps for multi-component assays
• doesn’t determine non-metals
• more expensive technique than FP