![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.](https://image.slidesharecdn.com/chapter19instrumentcomponents-140707142833-phpapp02/85/Chapter-19-instrument-components-23-320.jpg)
Chapter 19 instrument components
- 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
- 4. Instrument Components Light Source Detectable Output over wavelength region of interest Continuum Source Line Source From Skoog etal From Skoog, West, Holler
- 6. 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)
- 7. Instrument Components 2. Wavelength Selector Restrict radiation to a narrow band Two Types Filter – removes “wide” bands Monochromator
- 8. 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
- 10. Instrument Components Bandwidth – wavelength range passed by selector High Quality: ~ 0.1 nm (monochromator) Filter 50 nm From Skoog, West, Holler
- 11. Sample Container Holds the sample Must be transparent in the region of interest UV: Quartz Vis: Glass IR: Salt Crystals
- 12. 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
- 13. Instrument Components Radiation Detectors Stable Sensitive in region of interest Rapid Examples: Phototube Photomultiplier tube (most sensitive) Photodiode array (multichannel) CCD Heat detectors (IR)
- 14. Phototube From Skoog, West, Holler
- 15. PMT Why is it better then a phototube for measuring low light levels?
- 17. 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
- 18. Spec 20 From Skoog, West, Holler
- 19. Double Beam Spectrophotometer More complex Compensates for drifts in detector/source Wavelength range: 195-850 nm Bandwidth: 4 nm Photometric accuracy: 0.5%T
- 22. Photodiode Array 200-1000 nm Resolution 1-2 nm Time: 0.1 s No scanning From Skoog, West, Holler Advantages/Disadvantages?
- 23. 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.
- 24. 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.