UV Vis Spectroscopy Flashcards
Frequency Ranges
UV
Visable
IR
NMR
Spectroscopy
Production, measurement, interpretation of spectra from interaction of electromagnetic radiation with matter
Wave properties
Frequency
Wavelength
Amplitude
Dual nature of light
Acts as a wave and particle
Wavelength
Distance between two peaks or valleys on a wave
Wavenumber
Used for IR
1/wavelength
How does a spectrophotometer work?
Light source → light is separated out into different colors → filter → hits sample → detector
Absorption of radiation
Energy from a photon of electromagnetic radiation is transferred to sample
Absorption spectrum
Shows absorbance at different wavelengths
Take readings using wavelength of peak absorbance
Emission of radiation
Energy is released in the from of a photon of radiation
Fluorescence or phosphorescence
Emission of light by a substance that has absorbed an electromagnetic radiation
Absorption of electromagnetic radiation by a molecule → emit a photon of lower NRG
Applications of UV Vis
Randicity
Analyze minerals
Detect contaminants
UV wavelength range
200-350 nm
Vis wavelength range
350-700 nm
Transmittance
Ratio of light that enters and leaves the sample
Beer lambert law
Absorbance = absorptivity x path length x concentration
Only for dilute solutions
UV sample prep
Want a clear, transparent, homogenous sample
UV Vis: other things to keep in mind
Need a reference solution
Need the right cuvettes that don’t absorb the radiation
Microplate readers
96 samples at a time!
Can do kinetics, microbial growth
Chromogens
Chemicals that form colored compounds upon reaction with the compound of interest
React selectively
Form a soluble colored compound
Quantifying minerals
Concentration of a mineral determined from a standard curve
Samples must be ashed or pretreated
Soluble mineral reacts with chromagen to produce a stable, colored product
Colorimetric methods pros
Cheap
Simple
Accurate
