What's the difference between UV-visible and AAS?

[/0]

I kinda can't tell...

They both use lamps which emit wavelengths of light that the chemical absorbs, and in both cases an electron is excited.

They both have similar read-out graphs.

They both deal with metals, right?

Is the only difference that in AAS the sample is atomised through a flame whereas in UV it's in solution? Or is there more to it than just that...



Also,
One trial paper said AAS only operates over the colored bit of the spectrum, is that right? 


Thanks from an :idiot2:

[dekoyl]

I think UV-Vis spectroscopy can also deal with organic samples (and metals).

Absorption of ultraviolet and visible radiation in organic molecules is restricted to certain functional groups (chromophores) that contain valence electrons of low excitation energy.

[Mao]

AAS can deals with metallic atoms, it excites valence electrons.

UV-vis deal with molecules, it excites electrons in molecular orbitals (i.e. electrons in bonds)

UV-vis operates over UV and visible part of the spectrum, AAS operates in the visible spectrum.

UV vis uses a lamp that can generate a wide spectrum, and uses a monochromator to select the wavelength required for the analysis. AAS uses a metal cathode lamp (matching the sample) that can generate a few distinct wavelengths, and uses a monochromator to select one of these wavelengths.

UV vis analyses solutions, AAS analyses vapourised metal atoms.

UV vis is performed in dark (isolated environment), AAS is performed under normal conditions (ambient lighting doesn't affect it).

[arthurk]

i heard AAS was capable of uv light as well
as seen on tsfx 2009 multi choice

[Mao]

if the cathode lamp can produce those frequencies, then yes.

[arthurk]

how does a cathode lamp manage to produce such frequencies?

[Mao]

Cathode lamps are vapourised metal lamps [the metal is specific to what you are analysing]. The metal is excited, which then emits specific frequencies according to transition in energy levels between electron shells/orbitals. These frequencies are emitted by that metal, and can only be absorbed by the same metal as energy level between electron shell/orbital are unique for each element.