Chapter 20: Instrumentation
Major Components
Depends on Type of Experiment
Absorption
Fluorescence
Emission
Source
Wavelen...
http://www.youtube.com/watch?v=O39avevqndU
Instrument Components
Light Source
Detectable Output over wavelength region of interest
Continuum Source
Line Source
From ...
Common:
Visible: Tungsten filament Lamp (320-2500 nm)
UV- Deuterium Lamp (160-320 nm)
IR: Heated Inert Solid (Globar, Nern...
Instrument Components
2. Wavelength Selector
Restrict radiation to a narrow band
Two Types
Filter – removes “wide” bands
M...
Monochromator
A. Prism
B. Grating
•Lenses/mirrors to focus the radiation
•Entrance and exit silts to restrict unwanted rad...
Grating monochromator
Instrument Components
Bandwidth – wavelength range passed by selector
High Quality: ~ 0.1 nm (monochromator)
Filter  50 n...
Sample Container
Holds the sample
Must be transparent in the region of interest
UV: Quartz
Vis: Glass
IR: Salt Crystals
1. In the equation, A = εbc, what quantity is represented by "ε" ?
a) Absorptivity
b) Molar absorptivity
c) Path length
d)...
Instrument Components
Radiation Detectors
Stable
Sensitive in region of interest
Rapid
Examples:
Phototube
Photomultiplier...
Phototube
From Skoog, West, Holler
PMT
Why is it better then a phototube
for measuring low light levels?
Types of Instruments
Single Beam (Spectronic 20)
Double Beam (separated in time or space)
Multichannel
Single Beam Spectro...
Spec 20
From Skoog, West, Holler
Double Beam Spectrophotometer
More complex
Compensates for drifts in detector/source
Wavelength range: 195-850 nm
Bandwidt...
Photodiode Array
200-1000 nm
Resolution 1-2 nm
Time: 0.1 s
No scanning
From Skoog, West, Holler
Advantages/Disadvantages?
An 8.64 ppm solution of [FeSCN]Cl (149 g/mol) has a T of 0.295
at 580 nm when measured in a 1.00-cm cell. Calculate
the mo...
Cytochrome c has a molar absorptivity of 106,000 M-1
cm-1
.
A solution is prepared by diluting a 10.0 uM solution by a
hun...
Chapter 19 instrument components
Chapter 19 instrument components
Chapter 19 instrument components
Chapter 19 instrument components
Chapter 19 instrument components
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Chapter 19 instrument components

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Chapter 19 instrument components

  1. 1. Chapter 20: Instrumentation Major Components Depends on Type of Experiment Absorption Fluorescence Emission Source Wavelength Selector Sample Detector Signal Processor Most Common Placement depends on experiment
  2. 2. http://www.youtube.com/watch?v=O39avevqndU
  3. 3. Instrument Components Light Source Detectable Output over wavelength region of interest Continuum Source Line Source From Skoog etal From Skoog, West, Holler
  4. 4. Common: Visible: Tungsten filament Lamp (320-2500 nm) UV- Deuterium Lamp (160-320 nm) IR: Heated Inert Solid (Globar, Nernst Glower) AA: Hollow cathode lamp (line source)
  5. 5. Instrument Components 2. Wavelength Selector Restrict radiation to a narrow band Two Types Filter – removes “wide” bands Monochromator
  6. 6. Monochromator A. Prism B. Grating •Lenses/mirrors to focus the radiation •Entrance and exit silts to restrict unwanted radiation •Dispersing Element to produce the “monochromatic” radiation
  7. 7. Grating monochromator
  8. 8. Instrument Components Bandwidth – wavelength range passed by selector High Quality: ~ 0.1 nm (monochromator) Filter  50 nm From Skoog, West, Holler
  9. 9. Sample Container Holds the sample Must be transparent in the region of interest UV: Quartz Vis: Glass IR: Salt Crystals
  10. 10. 1. In the equation, A = εbc, what quantity is represented by "ε" ? a) Absorptivity b) Molar absorptivity c) Path length d) Concentration 2. Can one measure a smaller amount of a compound if it has a high or low absorptivity a) higher b) lower
  11. 11. Instrument Components Radiation Detectors Stable Sensitive in region of interest Rapid Examples: Phototube Photomultiplier tube (most sensitive) Photodiode array (multichannel) CCD Heat detectors (IR)
  12. 12. Phototube From Skoog, West, Holler
  13. 13. PMT Why is it better then a phototube for measuring low light levels?
  14. 14. Types of Instruments Single Beam (Spectronic 20) Double Beam (separated in time or space) Multichannel Single Beam Spectrophotometer Simple, Inexpensive Wavelength range: 340 – 625 nm Bandwidth: 20 nm Wavelength accuracy: 2.5 nm
  15. 15. Spec 20 From Skoog, West, Holler
  16. 16. Double Beam Spectrophotometer More complex Compensates for drifts in detector/source Wavelength range: 195-850 nm Bandwidth: 4 nm Photometric accuracy: 0.5%T
  17. 17. Photodiode Array 200-1000 nm Resolution 1-2 nm Time: 0.1 s No scanning From Skoog, West, Holler Advantages/Disadvantages?
  18. 18. An 8.64 ppm solution of [FeSCN]Cl (149 g/mol) has a T of 0.295 at 580 nm when measured in a 1.00-cm cell. Calculate the molar absorptivity coefficient for the complex at this wavelength.
  19. 19. Cytochrome c has a molar absorptivity of 106,000 M-1 cm-1 . A solution is prepared by diluting a 10.0 uM solution by a hundred. What would be the absorbance of the diluted solution if measured in a 1.00 cm cell.

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