Simultaneous selective extraction of nitramine explosives using molecularly imprinted polymer hollow spheres from post blast samples

Molecularly imprinted polymer hollow spheres (MIHSs) were produced by using hexanitrohexaazaisowurtzitane (HNIW or CL-20) as a template, silica nanospheres as a sacrificial matrix, acrylamide as a functional monomer, ethylene glycol dimethacrylate as a cross-linker and acetonitrile as a porogen at 4 °C under UV irradiation. This sorbent was applied to the selective solid-phase extraction (SPE) of several explosives simultaneously by using a newly-developed SPE procedure. For the first time, 2,4,6-trinitrotoluene (TNT), 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX), 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX) and CL-20 were selectively extracted and determined simultaneously from simulated post-blast samples prepared from motor oil and vacuum pump oil. The matrix effects were successfully eliminated and accurate quantization was achieved. When the loading amounts of HMX, RDX, TNT and CL-20 were, respectively, below 10, 2, 5 and 20 nmol for 100 mg of MIHS, these explosives were almost retrieved completely (above 98%). For the MIHSs and non-imprinted polymer hollow spheres (NIHSs), in acetonitrile and methanol, the imprinting factors (IFs) of CL-20 and tetraacetyldibenzylhexaazaisowurtzitane (TADB, a structural analogue of CL-20) changed dramatically, from 7.75 to 1.57 and 0.88 to 2.39, respectively. It highlighted the significant effect of solvents on imprinted sites.