Assessing the impact of background pyrolysis products on ignitable liquid comparisons /by Nichole Leeann Cruz.

Automated identification of ignitable liquids by comparison of gas chromatography-mass spectrometry (GC-MS) data could decrease the amount of time required to analyze fire debris case samples. Current chromatographic comparison techniques do not perform adequately for samples with pyrolysis products. A method was developed that used a set of linear transformations of the original GC-MS data to computationally add pyrolysis product data to ignitable liquid data. The test samples were used to evaluate automated methods of comparing ignitable liquids in the presence of pyrolysis products. The use of binned extracted ion chromatograms (EICs) significantly improved the correlation of ignitable liquids in the presence of pyrolysis products from synthetic materials with reference ignitable liquids. The algorithm accommodated up to a 70:30 ratio of the pyrolysis products relative to the ignitable liquid before the calculated Pearson correlation value was comparable to one obtained with a different ignitable liquid. The possibility of subtracting pyrolysis products from the background of impure ignitable liquid samples was evaluated and it was determined that the method will require that a robust alignment algorithm be developed to address differences in peaks shapes, peaks sizes and retention times. Better test samples and a larger variety of synthetic and natural materials will be required for optimizing the parameters of the ACCID algorithm for analyzing ignitable liquids mixed with pyrolysis product impurities