FORENSIC CHEMISTRY LABORATORY MANUAL

by R.Q. Thompson; Oberlin College

ANALYSIS OF CARPET SAMPLES FOR FLAMMABLES

Objective

To identify the flammable used, if any, to start a fire at the crime scene or elsewhere.

 

Sample

Simulated burned carpet from the fire's point of origin. Prepare the sample in the following way.

Place 40 drops flammable liquid on a carpet sample (1.5" x 1.5"), and set the carpet on fire with a match (in a pan in the fume hood). Douse the flame with water after 2 minutes. Shake the burned carpet sample to remove water, and then place it in a paint can. Seal and label the can.

 

Reagents

Set of flammables (10 mL each) -- ethanol, gasoline, kerosene, lighter fluid, paint thinner; DFLEX activated charcoal strips (Albrayco Laboratories; 500 Corporate Row, Cromwell, CT 06416) used to collect volatile organics; carpet remnant

 

Standard Reference Material

 

None

 

Method

 

Gas chromatography
Special equipment

Capillary gas chromatograph with DB-1 (methyl silane) or DB-5 (phenyl methyl silane) column and flame ionization detector; 1-pint unused paint cans (from paint store); adjustable-temperature oven ; 2-mL chromatography vials with screw caps

 

Procedure

For instructor (detailed) ; For student (brief)

 

Typical results

Chromatograms of gasoline vapor and kerosene vapor: 1 µL injection of liquid sample at a 1:40 split; temperature-programmed separation; 1 mL/min helium flow; DB-5 column (30-m length, 0.25-m i.d., 0.25-µm film thickness).

 

Alternate Method

Gas Chromatography - Mass Spectrometry

 

Procedure

(planned for next edition)