A mixture of explosives was analysed by gas chromatography (GC) linked to ultraviolet (UV) spectrophotometry that enabled detection in the range of 178 -330 nm. The gas phase UV spectra of 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (DNT), ethylene glycol dinitrate (EGDN), glycerine trinitrate (NG, nitroglycerine), triacetone triperoxide (TATP), pentaerytritol tetranitrate (PETN) were successfully recorded.The most interesting aspect of the current application is that it enabled simultaneous detection of both the target analyte and its decomposition products. At suitable elevated temperatures of the transfer line between the GC instrument and the UV detector, a partial decomposition was accomplished. Detection was made in real time and resulted in overlaid spectra of the mother compound and its decomposition product. Hence, the presented approach added another level to the qualitative identification of the explosives in comparison to traditional methods that relies only on the detection of the target analyte. As expected, the decomposition product of EGDN, NG and PETN was NO, while TATP degraded to acetone. DNT and TNT did not exhibit any decomposition at the temperatures used.UV detection in gas phase is a sensitive and selective universal detection that is suitable for identification and quantification. It is robust with easy maintenance, no moving parts, no ionization and no vacuum pumps. It is particularly useful for detection and identification of isomers.
KEYWORDS:Forensic science, ultraviolet detection, gas chromatography -ultraviolet spectrophotometry, ultraviolet spectra, explosive analysis, triacetone triperoxide, nitrate esters Gas chromatography with ultraviolet detection (GC-UV) is a hyphenation of gas chromatography and UV spectrophotometry in gas phase. The instrument INSCAN model 175, developed and built by Verner Lagesson and Ludmila Lagesson-Andrasko, was successfully employed in several studies (20,21). A spectral library containing more than 1400 gas phase UV spectra, as a basis for identification of compounds and determination of specific functional groups, was established.One of the GC-UV method advantages is an illustrative three dimensional presentation of the chromatogram. It is displayed at real time and the decomposition process can be followed visually on line. With benefit, this method can be employed in parallel with GC-MS for verification and as its complement. The simplicity and robustness of GC-UV is another advantage. It can easily be modified to a mobile design for use in the field or for continuous monitoring of industrial processes online. The GC-UV is excellent for identification of isomers and small gaseous molecules. On comparison with GC-IR detection, the sensitivity of GC-UV can be as much as 1000 times higher, depending on the 3 absorption properties of electronic spectra. The UV spectra in vapor phase are well defined because they are not influenced by solvent effects. Many substances show also vibrational fine structure overlaid to absorption bands. Thes...