Enhanced electrospray ionization mass spectrometric detection of hexamethylene triperoxide diamine (HMTD) after oxidation to tetramethylene diperoxide diamine dialdehyde (TMDDD).

Hexamethylene triperoxide diamine (HMTD) is one of the peroxide-based explosives that are difficult to detect using standard analytical methodologies. It was analyzed by electrospray ionization mass spectrometry (ESI-MS) on a UPLC-TOF instrument. Alkali metal salts were used to promote the formation of ions. In the full scan positive ion mode a 3 ng (13 pmol) limit of detection was achieved if [HMTD + Me](+) ions (Me = Li, Na, K) were detected. It was found that HMTD easily undergoes oxidation to tetramethylene diperoxide diamine dialdehyde (TMDDD) in the source as well as in the samples. TMDDD can be detected as [TMDDD + Me](+) ions, but better ionization efficiency leads to the detection limit of TMDDD at the 2 pg (0.01 pmol) level. In butyl acetate the yield of oxidation of HMTD to TMDDD reaches 25% within 20 min at 120 °C, which offers a simple way of improving the detection limit of HMTD by two orders of magnitude. A simple procedure of detection of HMTD that matches the most sensitive methods available was developed. It uses standard equipment available in many laboratories. It was shown that the frequently reported [HMTD-H](+) cation observed by various authors was in fact a misinterpretation of the results, and should be attributed to [TMDDD + H](+).