The use of mass spectrometric ion ratios for analyte identification is well accepted in drug testing and other laboratories.  In order for a positive identification of the analyte to be made (in analyses involving gas chromatography-mass spectrometry with electron impact), the two ion ratios for the analyte must fall within ± 20% of the same ion ratios in the control.  These criteria are part of a laboratory’s quality assurance program and are defendable in a court of law.  The goal of our work it to determine the applicability of ion ratio acceptance criteria to six gasoline target compounds for use in arson investigations. <br/>The ability to accurately determine the presence of an ignitable liquid (IL) found at an arson scene can give information about the fire’s cause. Its presence may indicate criminal activity. Conditions affecting a positive identification include the amount if IL that has been allowed to evaporate (a process called weathering which results in loss of lighter molecular weight compounds) and the substrate or matrix that the sample has been collected on.  Weathered samples result in chromatograms that differ from those of neat samples that are used for comparison for identification.  Currently, there is no explicit way to determine if a sample is too weathered to be identified as an IL.  This is left to the discretion of the analyst and is not defendable in a court of law.  Our goal is to take the subjectivity out of the assignment of weathered gasoline (the most common IL) by using ion ratio criteria to definitively identify six target compounds currently used, in addition to other qualitative data, in the identification of gasoline per the American Society for Testing and Materials 1618.<br/>Our study is the first to apply ion ratio acceptance critera to the identification of gasoline target compounds found in gasoline subjected to a variety of experimental conditions that one would come across as part of arson analysis.   We present these findings and comment on the incorporation of ion ratios into the identification process allowing analysts to go beyond pattern matching and instead use an identification process that relies on quantifiable data.

Use of peak ion ratios measured by gas chromatography-mass spectrometry for the quantitative determination of gasoline target compounds recovered from weathered gasoline spiked onto burnt nylon carpet for forensic purposes

2019 Spring National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.