INORGANIC ANALYSISINORGANIC ANALYSISChapter 6Chapter 6

Inorganic CompoundsInorganic Compounds

Compounds which do not contain carbonCompounds which do not contain carbon Metals- Tools, coins, weapons, metal scrapings, Metals- Tools, coins, weapons, metal scrapings,

paints, dyes, explosives, poisonspaints, dyes, explosives, poisons

Trace ElementsTrace Elements

Trace elements Trace elements (<1%)- “invisible” (<1%)- “invisible” markers, additional markers, additional points of comparisonpoints of comparison

Soil, fibers, glass, Soil, fibers, glass, metallic objects, hair, metallic objects, hair, paintpaint

AtomicAtomic StructureStructure

Nucleus- in the center, contains neutrons and Nucleus- in the center, contains neutrons and protons protons

Protons have a positive charge (1)Protons have a positive charge (1) Electrons have a negative charge (1/1837)Electrons have a negative charge (1/1837) Neutrons have a neutral charge (1) Neutrons have a neutral charge (1)

AtomicAtomic StructureStructure

Atomic number = the number of protons in Atomic number = the number of protons in the nucleus of an atom, the number the nucleus of an atom, the number identifies the element (also tells the identifies the element (also tells the number of electrons)number of electrons)

Atomic mass (mass number) = the number Atomic mass (mass number) = the number of protons + the number of neutronsof protons + the number of neutrons

Atomic StructureAtomic Structure

Atoms that differ from other atoms of the same Atoms that differ from other atoms of the same element by the number of neutrons in the nucleus element by the number of neutrons in the nucleus (have the same number of protons and (have the same number of protons and electrons)electrons)

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

Atomic StructureAtomic Structure

Electrons travel around the nucleus in orbital paths with Electrons travel around the nucleus in orbital paths with particular energy levelparticular energy level

Excited state- electrons pushed into higher orbitals Excited state- electrons pushed into higher orbitals (requires energy)(requires energy)

Atomic Absorption Spectrophotometry-Atomic Absorption Spectrophotometry- measures the measures the value & amount of light energy going into atomvalue & amount of light energy going into atom

Falls back after short period of time (releases energy)Falls back after short period of time (releases energy) Emission Spectroscopy-Emission Spectroscopy- collects & measures the various collects & measures the various

light energies given offlight energies given off E = hf : E = hf : Energy difference between orbitals equals Energy difference between orbitals equals

Planck’s Constant times frequency of light (absorbed or Planck’s Constant times frequency of light (absorbed or emitted)emitted)

Emission SpectroscopyEmission Spectroscopy

Emission Spectrum- light (energy) emitted from Emission Spectrum- light (energy) emitted from a source and passed through a prism is a source and passed through a prism is separated into its component colors or separated into its component colors or frequenciesfrequencies

Continuous Spectrum- all colors merge to form Continuous Spectrum- all colors merge to form continuous band (sunlight, incandescent)continuous band (sunlight, incandescent)

Line Spectrum- emitted as several individual Line Spectrum- emitted as several individual colored lines representing definite wavelengths colored lines representing definite wavelengths or frequencies (sodium lamp, mercury arc, neon)or frequencies (sodium lamp, mercury arc, neon)

Vaporized, excited matter emits characteristic Vaporized, excited matter emits characteristic line spectrum (“fingerprint” of elements)line spectrum (“fingerprint” of elements)

Emission SpectroscopyEmission Spectroscopy

Emission SpectroscopyEmission Spectroscopy

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

ICPICP

Inductively Coupled Plasma Emission Inductively Coupled Plasma Emission SpectrometrySpectrometry

Identifies and measures elements through Identifies and measures elements through light energy emitted by excited atoms using light energy emitted by excited atoms using hot plasma torch (argon gas)hot plasma torch (argon gas)

Radio- Frequency (RF) coil carries currentRadio- Frequency (RF) coil carries current Accepted method of identification and Accepted method of identification and

characterization of mutilated bullets and characterization of mutilated bullets and glass fragmentsglass fragments

Atomic Absorption Atomic Absorption SpectrophotometerSpectrophotometer

Light (energy) absorption of element (photon of Light (energy) absorption of element (photon of light interacts w/ an electronlight interacts w/ an electron jumps to higher jumps to higher orbital)orbital)

Higher conc. of element Higher conc. of element more light absorbed more light absorbed Quantitative (even trace elements)Quantitative (even trace elements) Determine one element at a timeDetermine one element at a time Graphite furnace or heated strip of metal Graphite furnace or heated strip of metal

increases efficiency and sensitivity (one-trillionth increases efficiency and sensitivity (one-trillionth of gram)of gram)

Simple, low costSimple, low cost

Neutron Activation AnalysisNeutron Activation Analysis

Nuclear energy- Nuclear energy- changing number of changing number of subatomic particlessubatomic particles

Radioactivity- emission Radioactivity- emission of radiation when of radiation when unstable nuclei unstable nuclei spontaneously spontaneously disintegrate (radioactive disintegrate (radioactive decay) decay)

Ex- radium, uranium, Ex- radium, uranium, thoriumthorium

RadioactivityRadioactivity

Three types of radiation:Three types of radiation:

1)1)Alpha rays- positively charged helium Alpha rays- positively charged helium atoms minus orbiting electrons atoms minus orbiting electrons

2)2)Beta rays- electronsBeta rays- electrons

3)3)Gamma rays-high energy form of Gamma rays-high energy form of electromagnetic radiation (*)electromagnetic radiation (*)

RadioactivityRadioactivity

Neutron Activation AnalysisNeutron Activation Analysis

Nondestructive method for identifying and Nondestructive method for identifying and quantitating trace elementsquantitating trace elements

Bombards w/neutrons, measures emitted Bombards w/neutrons, measures emitted gamma raysgamma rays

Extremely sensitive (nanogram)Extremely sensitive (nanogram) Simultaneous analysis for 20-30 elementsSimultaneous analysis for 20-30 elements Very expensive (nuclear reactor + analyzer)Very expensive (nuclear reactor + analyzer) Metals, drugs, paint, soil, GSR, hairMetals, drugs, paint, soil, GSR, hair

JFK AssassinationJFK Assassination

1963, Lee Harvey 1963, Lee Harvey Oswald, Warren Oswald, Warren CommissionCommission

3 shots from Texas 3 shots from Texas School Book Depository School Book Depository behind JFKbehind JFK

JFK hit by 2 bullets JFK hit by 2 bullets 1: back1: backthroatthroat

Gov. Connally Gov. Connally backback chestchest right wrist right wrist left left thighthigh

2: JFK’s skull (fatal)2: JFK’s skull (fatal)

JKF AssassinationJKF Assassination

Evidence in depository:Evidence in depository: * 6.5-mm military rifle w/Oswald’s * 6.5-mm military rifle w/Oswald’s palm printpalm print * 3 spent 6.5 mm cartridge cases* 3 spent 6.5 mm cartridge cases * Oswald seen in AM and minutes * Oswald seen in AM and minutes after shootingafter shooting * “Grassy knoll”?* “Grassy knoll”?

JFK AssassinationJFK Assassination 1977- Bullet, fragments and wounds 1977- Bullet, fragments and wounds

examined for trace elementsexamined for trace elements Western Cartridge Co./Mannlicher-Western Cartridge Co./Mannlicher-

Carcano bullets contain Carcano bullets contain antimony & silverantimony & silver Neutron Activation AnalysisNeutron Activation Analysis Stretcher and wrist bullet indistinguishableStretcher and wrist bullet indistinguishable Car and brain fragments indistinguishableCar and brain fragments indistinguishable Results consistent with findingsResults consistent with findings See Table 6-3 pg. 153See Table 6-3 pg. 153

X-Ray DiffractionX-Ray Diffraction

Identifies crystalline materials, how elements Identifies crystalline materials, how elements are combined into are combined into compoundscompounds

Solid, crystalline materials: definite, orderly Solid, crystalline materials: definite, orderly arrangement of atomsarrangement of atoms

95% of inorganic compounds95% of inorganic compounds Diffraction pattern formed by reflection of X-Diffraction pattern formed by reflection of X-

rays (“fingerprint”)rays (“fingerprint”) Not sensitive (<5 % of mixture)Not sensitive (<5 % of mixture) Ex- ExplosivesEx- Explosives

X-ray DiffractionX-ray Diffraction