The field recovery of explosive residues using solid-phase microextraction followed by chromatographic analysis

An inexpensive, rapid and sensitive method for the field pre-concentration and subsequent analysis of high explosives residues from solid debris samples and from aqueous samples has been evaluated using solid-phase microextraction (SPME). Explosives studied included nitrobenzene, 2-nitrotoluene, 3-nitrotoluene, 4-nitrotoluene, 2,6-dinitrotoluene, 1,3-dinitrobenzene, 2,4-dinitrotoluene, trinitrotoluene, 1,3,5-trinitrobenzene, 4-amimo-2,6-dinitrotoluene, 2-amino-4,6-dinitrotolene and tetryl. SPME/HPLC requires a special desorption apparatus to elute the extracted analyte onto the column at high pressures. Although the SPME procedures have generally proved to be inexpensive, reliable, and highly sensitive, SPME/HPLC has proven to be the most problematic. Analysis of the explosives by HPLC generally required specialized columns of high carbon loading, multiple columns or small column and particle size diameters for acceptable resolution. SPME followed by low injector temperature desorption into GC/ECD and GC/MS is shown to be a satisfactory method for the analysis of the explosives studied. The relative effects of controllable variables including fiber chemistry, absorption and desorption temperature, extraction time, and desorption time have been optimized. Explosives were detected at parts per trillion concentrations using the SPME method developed. The optimized method involves the extraction of the post-blast debris with an organic solvent followed by addition of high salt content water and SPME prior to chromatographic analysis. The technique can be used in the field utilizing commercially available portable chromatographic instruments.