Inorganic Analysis

Inorganic Evidence: Non-carbon-containing substances, often the physical evidence.
Forensic scientists analyze inorganics such as tools, coins, weapons, explosives, poisons, metal scrapings, and trace components in paints and dyes.
Many products contain small quantities of elements, known as trace elements, present in concentrations of less than 1 percent.
For the criminalist, the presence of trace elements is helpful because they provide “invisible” markers that may establish the source of a material
The forensic scientist must perform tests that will determine the specific chemical identity of the suspect material to the exclusion of all others.

Techniques available to forensic scientists for determining the elemental composition of materials are:

1. ==Atomic Emission Spectrophotometry (AES)→ Inductively coupled plasma== 2. __Atomic Absorption Spectrophotometry (AAS)__

Recall: molecules can be ABSORBED by UV, Vis or IR
Molecules can also EMIT radiation. * Forms the basis of two important analytical techniques * __Emission spectroscopy * ^^Atomic absorption spectroscopy__^^

Recall…atoms are composed of a nucleus (protons and neutrons) with electrons orbiting the nucleus * Energy Level: %%Orbits have a certain amount of energy%%
Each element has its own number of energy levels→ an atom will absorb a certain amount of energy

An emission spectrograph: * heats substance * gets “excited” * emits energy (light) * ^^based on what elements are in the substance, it will produce a unique line pattern^^

AES: convert samples to atoms * $By “exciting” them→bringing them to higher electronic states$

Inductively coupled plasma emission spectrometry (ICP): * The sample (aerosol) is heated (charged) * Charged particles emit light * Different wavelengths depend on what elements are present
==How is it used in forensics??== * ==Identification and characterization of mutilated bullets== * ==Identification and characterization of glass fragments==

\ b. Atomic Absorption

Atomic Absorption Spectrophotometry: * ^^Heat substances (“excites” atoms)^^ * ^^Expose it to radiation for a specific element^^

If the element is present, a portion will be absorbed

If want to detect a certain element can shine specific light patterns to see if the element present

\ Radioactive Decay: Unstable atoms will decompose

==Three types of radiation== * ^^Alpha rays^^ * $Beta rays$ * %%Gamma rays%%
Neutrons produce radioactive isotopes

measure gamma-ray energy (specific to the element)

%%Very sensitive→identifies and quantifies 20 to 30 trace elements.%%
How is it used in forensics? * Find trace elements in metals, drugs, paint, soil, gunpowder residue, and hair.
Since this technique requires access to a nuclear reactor, however, it has limited value to forensic analysis.

@@Provide elements present but no info about how elements are combined in a compound@@
So, aim a beam of X-rays at a crystal to study how they interact with the atoms * X-ray Diffraction * ^^ONLY applied to the study of solid, crystalline materials.^^ * ^^Fortunately, 95% of all inorganics are crystalline^^

X-rays penetrate the crystal→ some reflected→ combine to form light and dark bands * known as diffraction patterns
^^Every inorganic compound produces its own “fingerprint” of diffraction patterns^^