Fire debris sample analysis can be very complicated. The number of compounds in an ignitable liquid can vary from one (ex. toluene) to hundreds (ex. kerosene). There are many different ignitable liquids available to the general public, such as paint thinners, nail polish removers, fuel oils, and of course gasoline. In addition, there are rarer ignitable liquids such as specialty industrial solvents and jet fuels that are available to a more limited population.
Fire debris samples also produce volatile compounds that are not components of ignitable liquids – the analyst goes through extensive training to be able to tell the difference between compounds that naturally arise from burned materials, and those that come from ignitable liquids.
Each sample is run through a gas chromatograph-mass spectrometer (GC-MS). The GC portion of this instrument is what separates the compounds from each other, so that they may be analyzed separately. This is done by injecting the mixture into a very long, very thin column that has gas flowing through it. Different compounds will travel through this column at different speeds, separating from each other as they go. Once the compounds are separated, they enter the MS for analysis. The MS breaks the compound apart into fragments. Different compounds break into fragments differently. The combination of the time the compound enters the MS and the pattern produced by fragmentation of that compound allows the analyst to identify that compound.
Gas chromatograph / Mass Spectrometer