2. Forensic Toxicologist
identifies and analyzes poisons, drugs, and
chemicals
studies the effect of such substances on the
body
Important in helping medical examiner
determine cause of death in an autopsy
all the blood and tissue samples undergo a
toxicology screening.
3. Toxicology Tests:
Chromatography – separate and quantify
individual chemical compounds
Mobile phase – substance is dissolved in solvent
Stationary phase – dissolved substance is
passed through a finely divided adsorbent,
different compounds move at different speeds,
rates of adsorption are plotted on a chart.
4. Toxicology Tests:
Thin-Layer Chromatography (TLC) –
uses a glass or plastic plate covered with a thin
layer of finely ground adsorbent such as silica
gel or alumina
sample is deposited on the plate
locations of separated components are noted
after the solvent evaporates
5. Toxicology Tests:
Gas Chromatography – separates liquids
and gases
material is coated on fine clay or glass beads
and packed into a steel or copper column
column is heated above boiling point of liquid
gas pushes compounds through column
detectors measure emerging fractions
6. Toxicology Tests:
Mass Spectrometry – identifies the chemical
structure of an unknown substance
after separating a substance using gas chromatography
each component enters a vacuum chamber
the components collide with a beam of high-energy
electrons causing the component molecules to lose
electrons and become charged ions
they then pass through a magnetic or electric field where
they are separated according to their masses and can
be identified
8. At the Crime Scene
Crime scene
technicians can Fire accelerants
conduct field tests Blood
that detect many Explosives
chemical residues Gunshot residue
found at crime Drugs
scenes, in Cosmetic material
vehicles, or on Construction material
clothing
Trace metals
9. Types of chemical
evidence
Solids –
poisons, drugs, soil, cement, minerals, explo
sive residues, gunshot
residues, cosmetics, trace materials
Liquids – acids, gasoline, body
fluids, beverages, chemicals for drug
labs, cleaning fluids, medications, poisons
Gases – natural
gases, refrigerants, butane, propane, tear
gas, propellants