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Here is the question and answer out of an exam paper:

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Firstly, I thought UV-Visible can also use radiation in the visible spectrum. Also when analyzing sodium chloride (a molecule), then UV-Visible would be more appropriate than AAS, because AAS would be used for just Na (Sodium). Would I be wrong to have said UV-Visible?

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NaCl solution as you know is almost transparent in the VIS region, UV-VIS spectroscopy can be used to determinate concentration of soluble salt see J. Phys. Chem. A 2008, 112, 2242-2247 however UV part of the spectra is used instead of VIS part, so this does not fit the restrictions of your question.

Surely AAS has a greater sensibility and so is the best technique to use in this case.

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  • $\begingroup$ how would i know what "type" of compounds are transparent in the VIS region, for UV-VIS spectroscopy? Or is this type of question just expecting you to say AAS on the basis that UV-VIS may use the UV region of the emission of the spectrum... ? $\endgroup$ – confused Apr 11 '14 at 11:55
  • $\begingroup$ @confused yes it's a legitimate question, you can't know it from the structure if you don't have a Gaussian install in your brain. The rationale behind this question is that you are searching for 1 technique that suite for elemental analysis: AAS has a greater sensibility and you know for sure that can detect sodium. So however if for hypothesis NaCl could have a VIS spectra AAS is a better choice. $\endgroup$ – G M Apr 11 '14 at 12:24

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