CHEMISTRY SECTION

The chemistry section of the Laboratory analyzes evidence from suspected arson fires, bombings and unknown (non poisonous/non drug) substance cases. The evidence is analyzed by classical wet chemistry thru intricate instrumental analyses. Results obtained are compared to known samples previously tested. Members from the chemistry section have attended classes and workshops in arson analysis, post blast investigations and explosive residue analysis. They also participate in the training of investigators for the collection and preservation of arson and explosive evidence.

ARSON

The Connecticut State Forensic Laboratory analyzes submissions from 150-200 suspicious fires per year. These submissions originate from state and local fire marshals, fire departments and police departments.

Each submission undergoes a three step analysis process: extraction of volatiles, instrumental analysis and interpretation of results. Due to the nature of the materials commonly used in suspicious fires, the debris collected from a suspected arson scene is placed in an airtight can and sealed.

The extraction procedures require that the evidence in these cans be heated to liberate the volatile components. The volatiles are trapped in a charcoal tube under vacuum. Once this process is completed, the absorbed volatiles are eluted or flushed from the charcoal tube via a solvent into a small vial.

A portion of this extract is then injected into an analytical instrument. One instrument used is called a gas chromatograph. This instrument separates complex mixtures of compounds into recognizable patterns known as chromatograms. A second instrument is the gas chromatograph/mass spectrometer. This instrument not only separates complex mixtures into recognizable patterns known as total ion chromatograms but offers the additional capability of identifying individual components or selected groups of components in a mixture.

Once a sample has been run and a chromatogram generated, the results are then interpreted. The chromatogram generated is then compared to chromatograms of known compounds to determine what type of product might be present in the sample submitted.

CLASSIFICATION

Petroleum distillates are often used as accelerants in suspicious fires. An accelerant is any material that aids in the spread or intensity of the fire. Petroleum distillates are mixtures of hydrocarbons which are obtained by fractional distillation of crude oil. Gasoline is a man made petroleum product. Petroleum distillates are classified according to the boiling point of the hydrocarbon components. The following are examples of the different petroleum distillate and their classifications:

1. Low boiling range petroleum distillates may include cigarette lighter fluid and camp stove fuels.
2. Medium boiling petroleum distillates contain the largest number of commercial products such as paint thinner and charcoal lighter fluids. Kerosene is also included in this category.
3. Medium-to-high boiling petroleum distillates are number 2 fuel oil and diesel fuel.
4. High boiling petroleum distillates include motor oil and number 4 fuel oil.
5. Non petroleum distillate based flammable liquids can include organic solvents and painting products.

K-9 Assistance

Since 1984, the Forensic Science Laboratory has been involved in the arson canine training program. The arson trained canine can rapidly investigate possible points of origin. The canine can also pin point areas where possible flammable liquid residues are located. By using an arson canine, the submitting agency can reduce the number of submissions while improving the chance for a positive result.

EXPLOSIVES

The Laboratory receives approximately 15 to 20 explosive cases per year. Evidence from the blast site and surrounding area is submitted to the Laboratory for analysis. The evidence is thoroughly documented and the residues analyzed by wet chemistry and instrumental methods. Each type of explosive has a signature chemical make-up. Analysis of the residues from post blast evidence allows the examiner to determine what explosive material was used. Chemical residues are extracted from the post blast debris either by a water or organic solvent wash. It is the wash that is analyzed by traditional chemical and instrumental methods. It is also up to the examiner to determine the type of device and detonating mechanism whenever possible.

WET CHEMISTRY

Small amounts of the extracts are analyzed using chemical tests known as spot tests. Each spot test is for a particular ion or group of ions. Spot tests include color tests and crystal tests. Spot tests are considered screening tests and assist the examiner in determining the type of instrumentation needed to identify the explosive used.

GAS CHROMOTOGRAPHY/MASS SPECTROMETRY (GC/MS)

As with arson cases, extracts from debris can be analyzed by GC/MS. This technique is used mainly for high explosives (e.g. TNT). By utilizing the mass spec portion of this instrument, the examiner can identify the high explosive used. As with arson cases, the results obtained from these analyses are compared to known samples of explosives.

CAPILLARY ELECTROPHORESIS/ION CHROMOTOGRAPHY

Water extracts from low explosives can be analyzed by ion chromatography. This technique separates low explosive residues into their basic ionic components. Results of this analysis are compared to known low explosives.

HIGH PERFORMANCE LIQUID CHROMOTOGRAPHY (HPLC)

Organic solvent extracts from high explosives can be analyzed by HPLC. Components of high explosives can be separated into their basic elements. Results of this analysis are compared to known high explosive mixtures.

SCANNING ELECTRON MICROSCOPY

Samples taken directly from debris subjected to a low explosive can be analyzed by SEM. SEM is an instrument that analyzes particles that are characterized by their size, shape and elemental composition.

Based on the results of the above tests, the examiner is able to determine what type of explosive was used as well as the type of device and possible detenation source. No one test alone is used to determine such information as each test done provides one piece of the explosive puzzle.

IDENTIFICATION OF UNKNOWN SUBSTANCES

Numerous cases each year require the analyses of unknown substances. This can range from powders received in the mail to substances adhering to a piece of clothing. Basic chemical testing and instrumental techniques are used to determine the type of material present. Comparisons to known samples or library searches are needed to determine what material is present.

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