A computational study investigating the suitability of zigzag graphene nanoribbons to serve as selective chemical detectors for trinitrotoluene is presented. Using lithium adatoms as surface anchoring sites, we find that chemisorption of different chemical precursors serving in the trinitrotoluene synthesis process induces unique and distinguishable fingerprints on the electronic structure of the underlying nanoribbon. Furthermore, mixed adsorption of trinitrotoluene and its various chemical precursors may allow the determination of the specific synthesis route used to produce this commonly used explosive material. The understanding of the contaminant adsorption process gained in this study suggests that lithium-decorated graphene nanoribbons may serve as selective chemical detectors.