1. Atomic Emission Spectroscopy (AES)
Devon Brown
SUPA Forensics
Block 4

2. What Is AES?
A method of chemical analysis that measures the intensity of light emitted by the atoms of elements at specific wavelength

3. Chemical Principles
Electrons from a higher energy level drop to a lower energy level
Electron emits a photon of light to dispose of extra energy

4. How it Works Flame, spark, or plasma excites the electrons
Electrons jump to a higher energy level
As electrons return to ground state, they release a photon
Instrument measures intensity of photons and their wavelength
Determines elements present and they’re quantity

5. Emission Lines
The frequency of an atom moving from a high energy level to a lower energy level
Wavelengths of photons emitted create lines
Each element has unique emission lines
Qualifies elements present in sample

6. Emission Band
Graph of the intensity of the light emitted from a sample
Intensity is a function of the wavelength
Separates various elements by color (like emission lines)
Quantifies the amount of an element in a sample

7. Flame Atomic Emission Spectroscopy
Sample is in the form of a sprayed solution or gas
Flame heat evaporates solvent and breaks chemical bonds
Produces free atoms of the material
Heat changes atoms into electrically charge particles
Emit light as they lose energy
Wavelength of light characteristic to specific element
Light dispersed by a prism and detected in spectrometer

8. Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES)
Inductively coupled plasma produces excited ions
Ions and atoms radiate electromagnetically charged particles
Wavelengths produced correspond to a definite element

9. Uses
Determine the proportional quantity of a particular element in a given sample
Determine the elemental composition of an unknown sample
Study structures of atoms
Analyzing motor oils
Determine the presence of arsenic in food and metals in wine
Study trace elements that are bound to proteins

10. AES in Forensic Science

11. Uses Analyze trace elements in soil
Determine origin
Determine the composition of metallic and glass samples
Determine origin and/or manufacturer
Confirm a poison
Detect a drug

12. Evidence
Preparation: samples must be converted into highly excited free atoms
Solid samples (glass, soil, metal alloy)
Directly vaporize sample
Excite sample by using a laser pulse or spark between electrodes
Introduced to a exciting source by a semiliquid mixture or melted by a laser in a stream of gas
Liquid samples (bodily fluids, unknown solution)
Reduced to a fine spray
Carried to exciting source by flowing gas

13. Safety and Hazard Issues
Chemicals tested can be very dangerous
Keep away any flammable materials
Extreme temperatures
Glass and metal samples can have sharp edges
Biological samples can contain poisonous materials and disease

14. Difficulties/Interference
Self-absorption
Flame’s temperature is greatest at center – concentration of excited atoms greater at center
Atoms around outer edges not in the same state
Excited atom emits a photon – grounded atoms in outer regions of flame may absorb photon
Decrease the emission intensity

15. Limitations Originally: High possibility of chemical interaction
Need a fairly large sample
Sensitivity of instruments low
Instability of atomization source
Cannot conduct simultaneous or multi-elemental analyses
With the development of technology, most of these limitations have been overcome.

16. Advantages Disadvantages Equipment is more expensive
Several elements can be recorded at once
Higher temperatures means lower inter-element interference
Several elements can be analyzed from a very small sample
Nonmetals can be determined by plasma
Low concentration refractory compounds can be determined
High concentration range for plasma sources
Equipment is more expensive
Procedure is more complicated
More time consuming
Higher operating costs

17. Works Cited
“Atomic Spectroscopy.” Andor: An Oxford Instruments Company. Web. March 29, 2015.
Banerjee, Prasenjit. “Atomic Emission Spectroscopy.” Chemistry Learner. Web. March 17, March 30, 2015.
Cylinder, Drew. “Atomic Spectra.” UC Davis Chemwiki. chemwiki.ucdavis.edu. Web. March 29, 2015
Harvey, Davis. “Atomic Emission Spectroscopy.” UC Davis Chemwiki. chemwiki.ucdavis.edu. Web. March 29, 2015.
Rosen, Vasiliy, Ph.D. “Atomic Spectroscopy: Basic Principles and Instruments.” Slideshare. Web. March 28, March 29, 2015.
Scheeline, Alexander and Spudich, Thomas M. “Atomic Emission Spectroscopy.” Analytical Science Digital Library. Web. March 30, 2015.
Spencer, James T, Ph.D. An Introduction to Forensic Science: The Science of Criminalistics. Cengage Learning March 29, 2015
Stone, David C, Ph.D. “Atomic Spectroscopy: Intrumentation, Techniques, and Theory.” Chemistry University of Toronto. Web. May 7, March 29, 2015.
Troy, David B. The Science and Practice of Pharmacy. Remington books.google.com. Web. March 30, 2015.