Transcript 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
 Soil, fibers, glass,
metallic objects, hair,
paint
Atomic Structure
 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 Structure
 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 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 Structure
 Electrons travel around the nucleus in orbital paths with
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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 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 Spectroscopy
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
 Light (energy) absorption of element (photon of
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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
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Nuclear energychanging number of
subatomic particles
Radioactivity- emission
of radiation when
unstable nuclei
spontaneously
disintegrate (radioactive
decay)
Ex- radium, uranium,
thorium
Radioactivity
 Three types of radiation:
1)Alpha rays- positively charged helium
atoms minus orbiting electrons
2)Beta rays- electrons
3)Gamma rays-high energy form of
electromagnetic radiation (*)
Radioactivity
Neutron Activation Analysis
 Nondestructive method for identifying and
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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
 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
 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 Assassination
 1977- Bullet, fragments and wounds
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examined for trace elements
Western Cartridge Co./MannlicherCarcano 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
 Identifies crystalline materials, how
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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
X-ray Diffraction