Chemistry question

BL1993

What principles is atomic absorption spectrometry, IR spectroscopy and UV spectroscopy based on?

Also, if asked what secondary stage of sewage treatment is, would it be sufficient to say the biological oxidation of dissolved organic matter in the sewage as micro-organisms aerobically digest the waste?

hotfuzz2

BL1993 wrote: »

What principles is atomic absorption spectrometry, IR spectroscopy and UV spectroscopy based on?

Also, if asked what secondary stage of sewage treatment is, would it be sufficient to say the biological oxidation of dissolved organic matter in the sewage as micro-organisms aerobically digest the waste?

To seperate ions according to their mass by varying magnetic fields.

Yes and mention the activated sludge process too

BL1993

That's Mass spectrometry. Thanks for confirming the other bit.

DepoProvera

No, thats mass spectrometry. (Different ions are separated according o their masses(mass/charge ratio) when moving in a magnetic field)

AAS principle is: the amount of light absorbed is proportional to the concentration of the element.

I'd also mention the water is constantly churned in large aeration tanks (increasing the dissolved O2 content). Then it's passed to sedimentation tanks and the sludge is removed(used for fertilizer or anaerobically oxidised by bacteria to produce methane)

BL1993

Thanks a million! Got anything for UV and IR?

DepoProvera

I think they're based on the same principle.

partyatmygaff

BL1993 wrote: »

What principles is atomic absorption spectrometry, IR spectroscopy and UV spectroscopy based on?

Essentially they're all forms of spectroscopy where electromagnetic radiation (In the form of light) is passed through a sample and the quantity of light absorbed (And its wavelength) is used to identify substances.

AAS is primarily used for metallic substances (E.g. testing for the presence and quantity of heavy metals such as lead in water).

UV-Vis spectroscopy is used primarily for testing transition metals, highly conjugated organic molecules (A simple if inaccurate explanation is: "A lot of double bonds") and biological polymers such as DNA and protein. Only certain moieties absorb UV radiation.

IR Spectroscopy has a huge number of uses. Essentially, bonds within a molecule absorb IR radiation. Each type of bond vibrates and absorbs a specific amount of radiation at a specific wavelength. When a molecule is tested and IR spectra are generated, you can "fingerprint" a molecule by its bonds. The key thing to note about IR spectroscopy is that the amount of light absorbed is associated with bond vibration.

Also, if asked what secondary stage of sewage treatment is, would it be sufficient to say the biological oxidation of dissolved organic matter in the sewage as micro-organisms aerobically digest the waste?

Yes. You could also mention it's also known as the activated sludge process but IIRC that's not strictly speaking necessary to obtain full marks.

hotfuzz2

BL1993 wrote: »

That's Mass spectrometry. Thanks for confirming the other bit.

Oops! Sorry :P

BL1993

partyatmygaff wrote: »

Essentially they're all forms of spectroscopy where electromagnetic radiation (In the form of light) is passed through a sample and the quantity of light absorbed (And its wavelength) is used to identify substances.

So could I just say that the underlying principle is that the absorbance of electromagnetic radtion is proportional the concentration?

partyatmygaff

BL1993 wrote: »

So could I just say that the underlying principle is that the absorbance of electromagnetic radtion is proportional the concentration?

For the purposes of LC Chemistry, yes that's perfectly acceptable.