Question

1.How does a hollow cathode lamp work and why is it required by atomic absorption spectroscopy? Start with a diagram of the HCL and label the parts.

2.Sketch a generic energy level diagram and show how K, L, and M lines are generated.

3.Make a diagram of the stages of atomization and excitation that occur in an ICP torch.

4.Why is ionization suppressed in an ICP torch?

Answer 1

1.

Hollow cathode lamp (HCL) is the major light source for atomic absorption spectroscopy (AAS).

In HCL, a hollow cup is formed by a metal element which is to be determined and it is uses as cathod. A tungsten wire is used as anode. The two electrodes are sealed in a glass cylinder which is filled with an inert gas. A quartz or glass window is sealed on the end of the cylinder.

When applying high voltage between the two electrodes, cathode emits narrow and intense lines (emission spectrum). Inert gas atoms become ionized at the anode and are attracted at high velocity to the cathode. When the ions strike the cathode surface, some of the metal atoms displaced and are excited by collision with electrons. These excited metal atoms give the characteristic emission spectrum.