Arson Flashcards
Fire
rapid oxidation process with the evolution of heat and light
Explosion
sudden conversion of potential energy (chemical or mechanical) into kinetic energy with a production and release of gases under pressure
- has both high order and low order
higher order explosion
rapid pressure rise or high force explosion characterized by shattering the confining structure or container
low order explosion
a slow rate of pressurization or low-force explosion characterized by a pushing or dislodging the confining structure or container
Fire Debris
certain machines used to analyze debris to identify ignitable liquid and explosive residues
Extraction of Ignitable Liquid from fire debris
ignitable liquid residues (ILR) must first be isolated from the debris into a gaseous or liquid phase
What does ILR stand for/ mean
ignitable liquid residues
what are the different techniques to perform extraction of ILR
distillation
solvent extraction
headspace
adsorption
Distillation
obsolescence
Solvent Extraction
destructive
Headspace
nondestructive, screening technique
Adsorption
nondestructive, screening technique
Passive headspace concentration extraction with activated charcoal
most commonly used technique
Gas Chromotography- Mass Spectrometry
GC is the most suitable technique for separation
the detection of the analyte is achieved by utilizing Mass Spectrometry (MS)
Gas chromatography is the preferred technique for
separating the compounds in a complex mixture
based on their boiling points.
- The results are displayed as a graph showing a
number of peaks, one scale depicts the amount of
each component, the other the time taken for it to
emerge from the instrument (Retention time) - Under the same conditions, the time taken for the
component to emerge will always be the same.
Mass Spectrometry
complex chromatographic patterns can be simplified by passing the separated components through a mass spectrometer.
the mass spectrometer fragments each component into a collection of ions
each component has a unique collection of ions also referred to as its “chemical fingerprint”
What is a chemical fingerprint? in mass spec?
a unique collection of ions
analysis of extract
Ignitable liquids are usually composed of tens of hundreds of different compounds
analyzing the extract begins with separating its components and then detecting them
Interpretation of results
most important, difficult and delicate step of fire debris analysis
consists of reviewing and analyzing the data…determine whether or not an ignitable liquid is present
characterize the liquid present in the debris…ASTM internaionl
how does standard kerosene present?
eight evenly-
spaced major peaks, with a number
of minor intermediate peaks.
8 peaks are also present in a
chromatogram of diesel but in different proportions. Diesel also contains an additional eight evenly-
spaced peaks which emerge later from the instrument
