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AAS and UV-VS - Coggle Diagram
AAS and UV-VS
Atomic Absorption Spectroscopy (AAS)
How does it work?
Lamp of element being tested projects specific wavelength of light
Lamp light passes through flame and vaporised lamp element
Left over beam passes through slit and monochromator
Reading is absorption value and can be plotted and compared
Converts intensity to absorbance which can determine concentration and therefore amount present in sample
What does it determine about inorganic substances?
Tool for measuring concentration/amounts of metals in parts per million
Benefits
Very fast
Accurate to parts per million or lower
Limitations
Only works with metals
Can only analyse one element at a time
Examples of industry application
Testing the amount of lead in paint
Forensics (crime scenes)
Ultraviolet-Visible Spectrophotometry (UV-VS)
How does it work?
Quantitative measurement of light absorbed by a chemical compound
Amount of energy absorbed is directly proportional to the concentration of the absorbing material in solution
Utilises Beer-Lambert Law
A=εcl
A is the absorbance of the substance, expressed in mol/L
ε is called the molar absorptivity or extinction coefficient
c is the molarity
l is the path or cell length in centimetres
Different wavelengths of light is shot through the solution. When absorption occurs the amount of compound present can be determined
Absorption is graphed between specific ranges and the peaks correspond to different compounds
What does it determine about inorganic substances?
For inorganic it determines the concentration of metals or coloured species but to a lower degree of accuracy compared to AAS
For organic it can determine multiple groups of compounds or groups, as well as the primary elements of each
Benefits
Organic analytes readily absorb UV wavelengths making UV-VS have a broad usage
Can be used on coloured solutions
Can determine the concentrations of metals/ ions in aqueous solution as well
Limitations
To measure concentration it must be able to absorb...
UV between 400-200nm
Visible light between 760-400nm
This can be counteracted by making a coloured complex or altering oxidisation states
To make the process shorter one needs to have an idea of what chemical is being looked for
Examples of industry application
Forensics
Traditional Chemistry
Life Science
Microbiology
Food & Agriculture
Material Science
Optical Components
Pharmaceutical Research
Petrochemistry
Cosmetic Industry
Quality Control