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Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: dnbwise on November 17, 2005, 05:12:34 PM

Title: aas experiment
Post by: dnbwise on November 17, 2005, 05:12:34 PM

I have a printout from an aas experiment I did yesterday. I need to detail in my report the slit width used. The printout has various details on it, but doesn't say "slit width" but what is another term that may be synonymous with this? The paper has listed:

-instrument mode: flame
-spec mode: absorption
-wavelength: 589.0 nm
-high resolution: off
-lamp current: 75%
-signal type: continuous
-flame-type: air-c2h2
-bandpass: full 0.2
-measurement time: 4.0 secs
-fuel flow: 1.1 1/min
-etc

Title: Re:aas experiment
Post by: GCT on November 17, 2005, 08:14:53 PM

Quote from: dnbwise on November 17, 2005, 05:12:34 PM

I have a printout from an aas experiment I did yesterday. I need to detail in my report the slit width used. The printout has various details on it, but doesn't say "slit width" but what is another term that may be synonymous with this? The paper has listed:

-instrument mode: flame
-spec mode: absorption
-wavelength: 589.0 nm
-high resolution: off
-lamp current: 75%
-signal type: continuous
-flame-type: air-c2h2
-bandpass: full 0.2
-measurement time: 4.0 secs
-fuel flow: 1.1 1/min
-etc

instrumental bandpass is almost synonomous with slit width, at least its significance relates to slit width.  One can directly decrease the instrumental bandpass of a spectrometric instrument by decreasing the slit width, the bandpass relates to the FWHH for the final spectra obtained from a laser source.  For a basic instrumentation  , ignoring other effects of braodening, you can calculate the band width from the slit widths by referring to the entendue limiting slit (entrance or exit) and multiplying the slit width by the linear dispersion (monochromator).

Title: Re:aas experiment
Post by: dnbwise on November 25, 2005, 04:53:49 PM

thanks for the feedback. I have another question about aas that seems a bit vague to me, but it is on a practice exam for my final. What kind of chemical information samples does AAS not provide?

Title: Re:aas experiment
Post by: GCT on November 28, 2005, 03:51:47 PM

Quote from: dnbwise on November 25, 2005, 04:53:49 PM

thanks for the feedback. I have another question about aas that seems a bit vague to me, but it is on a practice exam for my final. What kind of chemical information samples does AAS not provide?

Your question is a bit unclear, maybe the following answers your question.

AAS is usually not employed with multicomponent analysis also it is limited somewhat (not the whole span of absorption spectroscopy) to atoms.  Also, one may have problems with chemical and spectral interference, particular with atoms with low IP AAS can be a problem and it has a limited dynamic range for quantitative analysis for most elements (due to the effect of slight polychromatic radiation, negative deviation....results in a limited linear range for application to beer's law).