CH4171-CH8-10 atomic spectroscopy with concept tests

CH4171-CH8-10 atomic spectroscopy with concept tests - CH...

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CH 8-10 Atomic Spectroscopy CH 8-10 Homework: Will not be collected 1. For Na and Mg + ions, compare the ratios of the number of ions in the 3p excited state to the number in the ground state at 1800 K, 2950 K, and 7250 K. 2. A 5.00 mL sample of blood was treated with trichloroacetic acid to precipitate proteins. After centrifugation, the resulting solution was brought to a pH of 3 and was extracted with two 5 mL portions of methyl isobutyl ketone containing the organic lead complexing agent APCD. The extract was aspirated directly into an air-acetylene flame yielding an absorbance of 0.444 at 283.3 nm. Five, 1 mL aliquots of standard solutions containing 0.250 and 0.450 ppm Pb were treated in the same way and yielded absorbances of 0.396 and 0.599. Calculate the concentration of Pb in the sample assuming Beer’s law is followed. 3. What is an internal standard and why is it used? 4. Describe three ways of introducing a sample into an ICP torch. 5. Why are ionization interferences less severe in ICP than in flame emission spectroscopy?
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CH 8-10 Atomic Spectroscopy Three common methods for identifying elements present in a sample: (1) Atomic Absorption/emission Spectroscopy Analysis of metals (2) Mass Spectrometry Analysis of metal complexes, particles, proteins, organic molecules (3) X-ray Spectroscopy Analysis of particles and surfaces
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Atomic Absorption and Emission Spectroscopy What are the atomic-level details behind this experiment? Sample is sprayed into a high-temperature atomizer to create gaseous atoms/ions, and then optical absorption/emission/fluorescence spectra are acquired. AA: Absorption of light source is measured. AF: Light source causes atomic fluorescence. AE: High T flame/plasma excites atoms which then emit.
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CH 8-10 Atomic Spectroscopy Atomic Energy Level Diagrams Recall the basic atomic energy level diagram. This diagram might lead one to believe that light-induced electronic transitions are very simple. They should be: (1) Narrow in wavelength. (2) Exactly equal to the differences in energy levels shown in the diagram.
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CH 8-10 Atomic Spectroscopy In reality, atomic absorptions are always broad (more than a single wavelength absorbed), and there are more absorptions than one would expect from the energy level diagram. Electric Pickle Na Doublet from an Electric Pickle
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Atomic Spectroscopy Note the splitting of the p level into a doublet. This is a magnetic field effect that occurs because electrons have spin, and any oscillating electric field produces a magnetic field. A single electron spins as it “orbits” the nucleus. Both the spin and orbit create magnetic fields. The direction of spin changes the way the spin magnetic field interacts with the orbital magnetic field. In fact, the observation of this “fine structure” was the first evidence of electron spin.
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This note was uploaded on 11/16/2011 for the course CHEM 4171 at Colorado.

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CH4171-CH8-10 atomic spectroscopy with concept tests - CH...

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