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INORGANIC ANALYSIS. Chapter 6. Inorganic Compounds. Compounds which do not contain carbon Metals- Tools, coins, weapons, metal scrapings, paints, dyes, explosives, poisons. Trace Elements. Trace elements (<1%)- “invisible” markers, additional points of comparison

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inorganic compounds
Inorganic Compounds
  • Compounds which do not contain carbon
  • Metals- Tools, coins, weapons, metal scrapings, paints, dyes, explosives, poisons
trace elements
Trace Elements
  • Trace elements (<1%)- “invisible” markers, additional points of comparison
  • Soil, fibers, glass, metallic objects, hair, paint
atomic structure
AtomicStructure
  • Nucleus- in the center, contains neutrons and protons
  • Protons have a positive charge (1)
  • Electrons have a negative charge (1/1837)
  • Neutrons have a neutral charge (1)
atomic structure1
AtomicStructure
  • Atomic number = the number of protons in the nucleus of an atom, the number identifies the element (also tells the number of electrons)
  • Atomic mass (mass number) = the number of protons + the number of neutrons
atomic structure2
Atomic Structure
  • Atoms that differ from other atoms of the same element by the number of neutrons in the nucleus (have the same number of protons and electrons)

Ex: hydrogen has 3 isotopes – all have 1 proton but each has a different # of neutrons)

atomic structure3
Atomic Structure
  • Electrons travel around the nucleus in orbital paths with particular energy level
  • Excited state- electrons pushed into higher orbitals (requires energy)
  • Atomic Absorption Spectrophotometry- measures the value & amount of light energy going into atom
  • Falls back after short period of time (releases energy)
  • Emission Spectroscopy- collects & measures the various light energies given off
  • E = hf : Energy difference between orbitals equals Planck’s Constant times frequency of light (absorbed or emitted)
emission spectroscopy
Emission Spectroscopy
  • Emission Spectrum- light (energy) emitted from a source and passed through a prism is separated into its component colors or frequencies
  • Continuous Spectrum- all colors merge to form continuous band (sunlight, incandescent)
  • Line Spectrum- emitted as several individual colored lines representing definite wavelengths or frequencies (sodium lamp, mercury arc, neon)
  • Vaporized, excited matter emits characteristic line spectrum (“fingerprint” of elements)
emission spectroscopy2
Emission Spectroscopy
  • Emission spectrograph- instrument which vaporizes, excites, (carbon electrode/ electrical arc) separates frequencies and records the line spectra of elements
slide11
ICP
  • Inductively Coupled Plasma Emission Spectrometry
  • Identifies and measures elements through light energy emitted by excited atoms using hot plasma torch (argon gas)
  • Radio- Frequency (RF) coil carries current
  • Accepted method of identification and characterization of mutilated bullets and glass fragments
atomic absorption spectrophotometer
Atomic Absorption Spectrophotometer
  • Light (energy) absorption of element (photon of light interacts w/ an electron jumps to higher orbital)
  • Higher conc. of element  more light absorbed
  • Quantitative (even trace elements)
  • Determine one element at a time
  • Graphite furnace or heated strip of metal increases efficiency and sensitivity (one-trillionth of gram)
  • Simple, low cost
neutron activation analysis
Neutron Activation Analysis
  • Nuclear energy- changing number of subatomic particles
  • Radioactivity- emission of radiation when unstable nuclei spontaneously disintegrate (radioactive decay)
  • Ex- radium, uranium, thorium
radioactivity
Radioactivity
  • Three types of radiation:
  • Alpha rays- positively charged helium atoms minus orbiting electrons
  • Beta rays- electrons
  • Gamma rays-high energy form of electromagnetic radiation (*)
neutron activation analysis1
Neutron Activation Analysis
  • Nondestructive method for identifying and quantitating trace elements
  • Bombards w/neutrons, measures emitted gamma rays
  • Extremely sensitive (nanogram)
  • Simultaneous analysis for 20-30 elements
  • Very expensive (nuclear reactor + analyzer)
  • Metals, drugs, paint, soil, GSR, hair
jfk assassination
JFK Assassination
  • 1963, Lee Harvey Oswald, Warren Commission
  • 3 shots from Texas School Book Depository behind JFK
  • JFK hit by 2 bullets

1: backthroat Gov. Connally back chest right wrist  left thigh

2: JFK’s skull (fatal)

jkf assassination
JKF Assassination
  • Evidence in depository:

* 6.5-mm military rifle w/Oswald’s

palm print

* 3 spent 6.5 mm cartridge cases

* Oswald seen in AM and minutes

after shooting

* “Grassy knoll”?

jfk assassination1
JFK Assassination
  • 1977- Bullet, fragments and wounds examined for trace elements
  • Western Cartridge Co./Mannlicher-Carcano bullets contain antimony & silver
  • Neutron Activation Analysis
  • Stretcher and wrist bullet indistinguishable
  • Car and brain fragments indistinguishable
  • Results consistent with findings
  • See Table 6-3 pg. 153
x ray diffraction
X-Ray Diffraction
  • Identifies crystalline materials, how elements are combined into compounds
  • Solid, crystalline materials: definite, orderly arrangement of atoms
  • 95% of inorganic compounds
  • Diffraction pattern formed by reflection of X-rays (“fingerprint”)
  • Not sensitive (<5 % of mixture)
  • Ex- Explosives
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