[Dolphinsiu]

Hollow cathode lamp is used instead of much simpler tungsten lamp as light source in atomic absorption (AA) measurement.Why?

I think that HCL consists of sealed but hollow cylinderical tubing (filled with nitrogen gas due to its inertness) with Pt anode and Y-shaped cathode made of the interest element. Hence, only line source of element is emitted at a certain wavelength. Since HCL is operated at low current, the line emission is more or less the same as the line absorption profile, light due to scattering or reflection is minimized. Also, as tungsten lamp is only useful in visible light but not UV absorption, but vice versa in HCL.

Is my answers correct, or not enough detailed/prefect?

[ARGOS++]

Dear Dolphinsiu;

With only a few exceptions: You are right!

The bulbs are filled with low pressure Argon and not Nitrogen, because its higher Ionisation energy and better inertness.
The emission lines have a much smaller HHW (Half height width) as the absorption of the atoms.

What makes the HCL very, very attractive are (but not lonely):

• -   Significant lower detection limits then in the Emission Spectroscopy (Boltzman).
• -   High Selectifity ( =  no continuous spectrum, small HHW).
• -   Less interferenced then Emission Spectroscopy (other elements, phys., etc).
• -   Multi Element HCL’s.
• -   Relatifly low price.

Your statement about tungsten lamp is correct, but HCL are not useful in UV/Vis because the high element selectifity.

I hope this may be of help to you.


Good Luck!
                   ARGOS⁺⁺

[Dolphinsiu]

o I see. Thank you!