Detection of explosive vapors from TNT buried in sand by gas chromatography and tunable electron energy monochromator-mass spectrometry using HS-SPME
The finding of buried explosives by detecting vapors emanating from explosives requires using a method that has high sensitivity and selectivity. In this work the results of an alternative methodology for explosive vapor detection based on GC-μECD is reported. A JEOL GCmate II - mass spectrometer coupled to a Tunable Electron Energy Monochromator (GC/TEEM-MS) was used for detected explosives identification. Both used the technique known as solid phase microextraction (SPME) in headspace (HS) mode to collect vapors above the samples. SPME is a simple technique that integrates sampling, extraction, concentration and sample introduction into a single step. Initially the optimum parameters for SPME were determined with the aim of obtain a high-quality extraction. The parameters were, type of SPME fiber, exposure time and desorption time in the port injection of the GC. HS-SPME procedure was carried out in samples with crystals of TNT buried in sand. These samples were analyzed under different environmental conditions such as temperature and water content. Analyses at several times after the TNT-soil mixture preparation were carried out during 1 month. Vapors of TNT and 2,4-DNT were found predominantly in the samples. HS-SPME coupled with GC-μ ECD and GC/TEEM-MS exhibited excellent selectivity and sensitivity.