Got a Match? Ion Extraction GC–MS Characterization of Accelerants Adsorbed in Charcoal Using Negative Pressure Dynamic Headspace Concentration

An undergraduate organic chemistry experiment demonstrating real-life application of GC–MS to arson accelerant identification is described. Students are given the task of comparing a sample recovered from a “crime scene” to that from a “suspect’s clothing”. Accelerants subjected to different conditions are recovered using a quick and simple negative pressure dynamic headspace method. GC–MS data is acquired. Students apply ion-extraction techniques and spectral library searches in conjunction with mass spectral fragmentation pattern analyses to classify accelerants according to an ignitable liquid classification scheme similar to that used by the American Society for Testing and Materials. After classification, they are asked to make a determination about the degree (or lack thereof) of match between samples and address several critical thinking issues regarding a suspect’s possible innocence or guilt.