![Page 1: Chapter 13 An Introduction to Ultraviolet/Visible Molecular Absorption Spectrometry](https://reader033.vdocuments.mx/reader033/viewer/2022061618/5519e54b550346443e8b5120/html5/thumbnails/1.jpg)
Chapter 13
An Introduction to Ultraviolet/Visible Molecular Absorption Spectrometry
![Page 2: Chapter 13 An Introduction to Ultraviolet/Visible Molecular Absorption Spectrometry](https://reader033.vdocuments.mx/reader033/viewer/2022061618/5519e54b550346443e8b5120/html5/thumbnails/2.jpg)
Terms & Symbols
![Page 3: Chapter 13 An Introduction to Ultraviolet/Visible Molecular Absorption Spectrometry](https://reader033.vdocuments.mx/reader033/viewer/2022061618/5519e54b550346443e8b5120/html5/thumbnails/3.jpg)
Beer’s Law
log Po/P = ebc = A
The derivation of this law assumes
a) That the incident radiation is monochromatic.
b) The absorption occurs in a volume of uniform cross-section.
c) The absorbing substances behave independently of each other in the absorbing process.
![Page 4: Chapter 13 An Introduction to Ultraviolet/Visible Molecular Absorption Spectrometry](https://reader033.vdocuments.mx/reader033/viewer/2022061618/5519e54b550346443e8b5120/html5/thumbnails/4.jpg)
Beer’s Law
Limitations to Beer’s LawReal Limitations to Beer’s Law Apparent Chemical Deviations Apparent Instrumental Deviations with
Polychromatic Radiation Instrumental Deviations in the Presence
of Stray Radiation
![Page 5: Chapter 13 An Introduction to Ultraviolet/Visible Molecular Absorption Spectrometry](https://reader033.vdocuments.mx/reader033/viewer/2022061618/5519e54b550346443e8b5120/html5/thumbnails/5.jpg)
The Effects of Instrumental Noise on Spectrophotometric Analyses Types of Noise Shot noise – This noise is generated by current flowing across
a P-N junction and is a function of the bias current and the electron charge. The impulse of charge q depicted as a single shot event in the time domain can be Fourier transformed into the frequency domain as a wideband noise.
Thermal noise – In any object with electrical resistance the thermal fluctuations of the electrons in the object will generate noise.
White noise- The spectral density of thermal noise is flat with frequency.
Burst noise – Occurs in semiconductor devices, especially monolithic amplifiers and manifests as a noise crackle.
![Page 6: Chapter 13 An Introduction to Ultraviolet/Visible Molecular Absorption Spectrometry](https://reader033.vdocuments.mx/reader033/viewer/2022061618/5519e54b550346443e8b5120/html5/thumbnails/6.jpg)
The Effects of Instrumental Noise on Spectrophotometric AnalysesTypes of Noise Avalanche noise – Occurs in Zener diodes are reversed
biased P-N junctions at breakdown. This noise is considerably larger than shot noise, so if zeners have to be used as part of a bias circuit then they need to be RF decoupled.
Flicker noise – This noise occurs in almost all electronic devices at low frequencies. Flicker noise is usually defined by the corner frequency FL.
Sources of Noise Case I: sT = k1
Case II: sT = k2(T2 + T) ½
Case III: sT = k3T
![Page 7: Chapter 13 An Introduction to Ultraviolet/Visible Molecular Absorption Spectrometry](https://reader033.vdocuments.mx/reader033/viewer/2022061618/5519e54b550346443e8b5120/html5/thumbnails/7.jpg)
The Effects of Instrumental Noise on Spectrophotometric Analyses
Effect of Slit Width on Absorbance Measurements
![Page 8: Chapter 13 An Introduction to Ultraviolet/Visible Molecular Absorption Spectrometry](https://reader033.vdocuments.mx/reader033/viewer/2022061618/5519e54b550346443e8b5120/html5/thumbnails/8.jpg)
Instrumentation
Instrument ComponentsSourcesWavelengths selectorsSample containersRadiation detectorsSignal processors and readout devices
![Page 9: Chapter 13 An Introduction to Ultraviolet/Visible Molecular Absorption Spectrometry](https://reader033.vdocuments.mx/reader033/viewer/2022061618/5519e54b550346443e8b5120/html5/thumbnails/9.jpg)
Instrumentation
Sources- Light sources
Deuterium and Hydrogen Lamps
Tungsten Filament Lamps
Tungsten Filament Lamps
![Page 10: Chapter 13 An Introduction to Ultraviolet/Visible Molecular Absorption Spectrometry](https://reader033.vdocuments.mx/reader033/viewer/2022061618/5519e54b550346443e8b5120/html5/thumbnails/10.jpg)
Instrumentation
Types of InstrumentsSingle-beamDouble-beam in spaceDouble-beam in timeMultichannel
![Page 11: Chapter 13 An Introduction to Ultraviolet/Visible Molecular Absorption Spectrometry](https://reader033.vdocuments.mx/reader033/viewer/2022061618/5519e54b550346443e8b5120/html5/thumbnails/11.jpg)
Instrumentation
Single-Beam Instruments
![Page 12: Chapter 13 An Introduction to Ultraviolet/Visible Molecular Absorption Spectrometry](https://reader033.vdocuments.mx/reader033/viewer/2022061618/5519e54b550346443e8b5120/html5/thumbnails/12.jpg)
Instrumentation
Double-Beam Instruments
![Page 13: Chapter 13 An Introduction to Ultraviolet/Visible Molecular Absorption Spectrometry](https://reader033.vdocuments.mx/reader033/viewer/2022061618/5519e54b550346443e8b5120/html5/thumbnails/13.jpg)
Instrumentation
Typical InstrumentsPhotometersVisible PhotometersProbe-type PhotometersUltraviolet Absorption PhotometersSpectrophotometers
![Page 14: Chapter 13 An Introduction to Ultraviolet/Visible Molecular Absorption Spectrometry](https://reader033.vdocuments.mx/reader033/viewer/2022061618/5519e54b550346443e8b5120/html5/thumbnails/14.jpg)
Instrumentation
Most common spectrophotometer: Spectronic 20.
1. On/Off switch and zero transmission adjustment knob
2. Wavelength selector/Readout
3. Sample chamber
4. Blank adjustment knob
5. Absorbance/Transmittance scale
![Page 15: Chapter 13 An Introduction to Ultraviolet/Visible Molecular Absorption Spectrometry](https://reader033.vdocuments.mx/reader033/viewer/2022061618/5519e54b550346443e8b5120/html5/thumbnails/15.jpg)
InstrumentationVisible Region
![Page 16: Chapter 13 An Introduction to Ultraviolet/Visible Molecular Absorption Spectrometry](https://reader033.vdocuments.mx/reader033/viewer/2022061618/5519e54b550346443e8b5120/html5/thumbnails/16.jpg)
Instrumentation Single-Beam Instruments for the Ultraviolet/Visible
Region
![Page 17: Chapter 13 An Introduction to Ultraviolet/Visible Molecular Absorption Spectrometry](https://reader033.vdocuments.mx/reader033/viewer/2022061618/5519e54b550346443e8b5120/html5/thumbnails/17.jpg)
InstrumentationSingle-Beam Computerized
Spectrophotometers
Inside of a single-beam spectrophotometer connected to a computer.
![Page 18: Chapter 13 An Introduction to Ultraviolet/Visible Molecular Absorption Spectrometry](https://reader033.vdocuments.mx/reader033/viewer/2022061618/5519e54b550346443e8b5120/html5/thumbnails/18.jpg)
Instrumentation Double-Beam
Instrumetents Double-Dispersing
Instruments Diode Array
Instruments
![Page 19: Chapter 13 An Introduction to Ultraviolet/Visible Molecular Absorption Spectrometry](https://reader033.vdocuments.mx/reader033/viewer/2022061618/5519e54b550346443e8b5120/html5/thumbnails/19.jpg)
References http://www.anachem.umu.se/jumpstation.htm http://userwww.service.emory.edu/~kmurray/mslist.html http://www.anachem.umu.se/jumpstation.htm http://userwww.service.emory.edu/~kmurray/mslist.html http://www.anachem.umu.se/jumpstation.htm http://www1.shimadzu.com/products/lab/spectro/uv3150.html http://www.perten.com/product_range/diode_array/da_technology.html http://repairfaq.ece.drexel.edu/sam/CORD/leot/course10_mod03/mod10-
03.html http://las.perkinelmer.com/catalog/Product.aspx?ProductID=L950 http://www.olisweb.com/products/upgrades/ir983.php http://imagers.gsfc.nasa.gov/ems/visible.html http://biology.easternct.edu/courses/spectwenty.htm http://www.cairnweb.com/systems/prod_lamp.html http://www.odyseus.nildram.co.uk/RFIC_Theory_Files/Noise_Tutorial.pdf