Profiling of volatile impurities in tetramethylenedisulfotetramine (TETS) for synthetic-route determination

This study investigated the feasibility of using volatile impurities from the rodenticide tetramethylenedisulfotetramine (TETS) for the discrimination of TETS produced by three synthetic routes. Each route was used to make one batch of TETS by reacting sulfamide with one of three formaldehyde analogs in the presence of either trifluroacetic acid (TFA) or hydrochloric acid. Ten impurities useful for differentiating the three TETS batches were discovered and tentatively identified by headspace solid-phase microextraction comprehensive two-dimensional gas chromatography–mass spectrometry (HS-SPME/GC × CG–MS). Of the ten identified impurities, the alkyl trifluoroacetate and alkyl chloride impurities distinguished TETS routes based on their use of either TFA or HCl as catalyst. On the other hand, four 6-carbon ketone impurities appeared to be batch specific rather than route specific and hence potentially useful for sample matching. Interestingly, 1,3,5-trioxane was not found in the TETS batch where it was used as a reactant, but instead was found in the two batches that did not have 1,3,5-trioxane as the reactant. In brief, the limited work discussed in this paper supports: (1) the feasibility of sampling and detecting volatile organic impurities from a solid chemical-threat agent, (2) the probable forensic benefit of catalysts acting as reactants in side reactions, (3) the uniqueness of a synthetic batch's impurity profile for potential sample matching, and (4) the possibility that some impurities, such as formaldehyde analogs, are not forensically helpful and may lead to an incorrect estimate about the synthetic route if not supported by sound chemical knowledge.