Exp 8 - Lab Manual: Atomic Absorption & Emission...

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Lab Manual: Atomic Absorption & Emission Spectrometry 1 Atomic Spectrometry (I) Absorption Mode (II) Emission Mode Part I – Absorption Mode INTRODUCTION & THEORY The first step is to find an analytical textbook and/or go online to read up on the theory of spectroscopy, in general, atomic absorption spectrometry, in particular. In this part of the experiment, the absorption mode will be used to determine the amount of calcium that is present in dry cereal. The experiment is described in the article “Determination of Calcium in Cereal with Flame Atomic Absorption Spectroscopy” by Ali Bazzi, Bette Kreuz, and Jeffrey Fischer, J ournal of Chemical Education volume 81, 1042 (2004). You should have gotten this paper before. If not, go back to the Assignment of Buret Preparation and Calibration and redo postlab problem #10. Study this paper carefully so that you know, for example, what other chemical problems have been studied by this method, how it is used to determine the amount of calcium in dry cereal, how the results shown in the paper are calculated, what sort of results are obtained (at the University of Michigan-Dearborn), and how they are relevant to one’s everyday life. MATERIALS & METHODS Once you have acquired a good understanding of the paper, go to WebCT and obtain the detailed procedure given in the form of slides (Lab Manual Atomic Absorption Spectrometry Supp). A number of relevant problems are given in these slides. When you correlate the slides and the paper, you will find that the experimental procedure is not exactly the same. Make a note of the differences. There may be further changes which will be announced by your TA in the lab. It is the procedure described in the slides NOT what is given in the article that you need to follow. The procedural changes are necessary to fit our situation (e.g., equipment we have, our class size, waste management, etc.). Part II – Emission Mode INTRODUCTION & THEORY Obtain an analytical chemistry textbook and/or go on the internet and search for some information on the basic theory of spectroscopy and the difference between atomic absorption and emission spectrometry. Following provides some basic background for flame atomic emission spectroscopy. Compounds give broad absorption spectra while elements give thin line spectra (see Figure 1 below). This is due to the fact that individual atoms do not have the rotational and vibrational modes that atoms attached in compounds have. The absorption of energy by individual atoms can result in only electronic transitions, which are quantized and therefore result in line spectra. Either the absorption or the emission of the energy when the atom's electrons fall back to the ground state can be used for analysis. The wavelength of absorption (or emission) can be used to identify the element (qualitative data) and the intensity of absorption (or emission) can be used to determine the amount of element present in a sample (quantitative data).
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This note was uploaded on 06/02/2011 for the course CHEM 100A taught by Professor Dai during the Winter '06 term at UCSD.

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Exp 8 - Lab Manual: Atomic Absorption & Emission...

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