Chemistry 366 Widener Molecular Ultraviolet and Visible Spectroscopy to answer 3 Qs in instrumental analysis all are in the attached file Chemistry 366 Hom

Chemistry 366 Widener Molecular Ultraviolet and Visible Spectroscopy to answer 3 Qs in instrumental analysis all are in the attached file Chemistry 366 Homework Problem Set
Widener University
Dr. Van Bramer
March 2019
Molecular Ultraviolet and Visible Spectroscopy Problem Set
1. Look at the information below to compare the wavelength range and intensity for deuterium, quartz
halogen, and Xe arc lamps. Additional information is available in the shared files for campus cruiser.
Use this information to identify:
a. Which lamp would you select to use for an instrument in the visible range? Why?
b. Which lamp would you select to use for an instrument that works for UV and VIS range?
Why?
Duterium Lamp http://www.newport.com/images/webclickthru-EN/images/1007.gif
Quartz Halogen Lamp – from: http://www.newport.com/images/webclickthru-EN/images/1016.gif
Xe Arc Lamp from http://www.newport.com/images/webclickthru-EN/images/1012.gif
2. Monochrometers involve tradeoffs between the spectral range, spectral resolution, transmission
efficiency, and design wavelength. Use the technical information available at the ocean optics
www.oceanoptics.com web sites. See the optical layout for a spectrometer: http://bit.ly/1KOlszu
Answer the following for a USB optical bench.
a. If you increase the number of grooves per mm, what happens to the resolution and spectral
range?
b. What happens to the resolution and spectral range when the slit width is reduced?
Chemistry 366 Homework Problem Set
Widener University
Dr. Van Bramer
March 2019
3. You are preparing to analyze a mixture with two different components. Based on the spectra in
figure 1.
a. Determine ?max and ? for compound A. Then calculate ? and E for ?max.
b. What would happen if you switched from a quartz cuvette to a glass cuvette for this
experiment?
c. What would happen to the spectrum in figure 1 if you took four times the number of scans
that you average? Describe the change and sketch what this new spectrum would look like.
d. Estimate the LOD for compound A and explain how you determined this answer.
e. The spectrum was acquired using a spectrometer with a deuterium and tungsten lamp, a
grating with the following specifications:
i. Wavelength range: 200-850 nm
ii. Grating:
600 lines/mm, set to 200-850 nm (blazed at 300 nm)
iii. Slit:
25 µm
iv. Optical resolution:
1.5 nm FWHM
Explain what would happen to the optical resolution and the tradeoffs involved if the slit width is
increased to 50 µm.
Spectrum
Absorbance
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
-0.1200
250
300
350
400
-0.2
Wavelength (nm)
Figure 1 – Spectrum of 2.75×10-5 M compound A in 1 cm cell
450

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