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INORGANIC ANALYSIS

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 ANALYSIS

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  1. INORGANIC ANALYSIS Chapter 6

  2. Inorganic Compounds • Compounds which do not contain carbon • Metals- Tools, coins, weapons, metal scrapings, paints, dyes, explosives, poisons

  3. Trace Elements • Trace elements (<1%)- “invisible” markers, additional points of comparison • Soil, fibers, glass, metallic objects, hair, paint

  4. 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)

  5. 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

  6. 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)

  7. 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)

  8. 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)

  9. Emission Spectroscopy

  10. Emission Spectroscopy • Emission spectrograph- instrument which vaporizes, excites, (carbon electrode/ electrical arc) separates frequencies and records the line spectra of elements

  11. 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

  12. 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

  13. 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

  14. 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 (*)

  15. Radioactivity

  16. 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

  17. 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)

  18. 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”?

  19. 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

  20. 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

  21. X-ray Diffraction

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