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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


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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