A gas chromatography method, coupled with diode array photometric spectral detection in the ultraviolet region (167-330 nm), was developed for the analysis of the gas phase of cigarette smoke. The method enabled us to identify more than 20 volatiles present in the vapor phase of cigarette smoke. In that way, all major volatile organic compounds (including aldehydes, conjugated dienes, ketones, sulfides, furans, and single-ring aromatics), as well as nitric oxide (NO) and hydrogen sulfide (H(2)S), can be analyzed in a straightforward manner through a single chromatographic run of <50-min duration. The method can easily be applied by the introduction of a small volume of the gas-phase stream into the GC injection loop directly through the smoking apparatus exhaust circuit, thus providing an excellent alternative to available methods, which usually require extraction or concentration steps prior to any chromatographic analysis. Furthermore, all problems concerning aging of the gas phase are eliminated. Twelve compounds (including NO) were chosen for quantification through the use of appropriate calibration standards. Comparison of the vapor phase yields of these compounds for the reference cigarette Kentucky 1R4F with already reported data indicates that this method is very reliable as far as accuracy and reproducibility of the results are concerned. Finally, the proposed methodology was used to compare the concentration of these cigarette smoke gas-phase constituents among individual puffs.

A novel instrument, which combines gas chromatographic separation with ultraviolet detection, has been employed in the qualitative study of molecular UV absorption spectra in the gas phase. The wavelength range available with the current instrument made studies in the region of 168-330 nm possible. The absorption spectra between 168 and 330 nm for ∼1000 organic compounds and a number of inorganic gases were registered. For all the spectra recorded, 69% showed absorption maxima shorter than 190 nm, and as much as 87% shorter than 200 nm. This indicates the importance of the short UV wavelength region for analytical purposes. The results showed that each compound studied gave rise to unique absorption spectra. The influence of temperature on the shape of the spectra was studied in the range of 15-205 °C. A slight broadening effect on spectral absorption bands (0.3 nm) and the vibrational structure (maximally 1.4 nm) with increased temperature was observed. However, this effect was shown to have no influence on the analytical results. In the vast majority of cases, where structural isomers were investigated, there were clear differences between the recorded spectra. Compounds with the same functional group showed pronounced similarities. The influence of conjugation and various substituents could be demonstrated. A commercial computer program was used for a computer search of unknowns against the recorded reference spectra. This showed that the gas-phase UV spectra are very well defined and that a search always resulted in a very close agreement, even if concentrations and chromatographic conditions were different between the recording of reference and unknown. When a search was performed on a compound not present in the library, the result pointed out the correct class of compounds.

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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...

This instrument consists of a gas flow cell with a small, built-in gas chromatograph. The dimensions are such that it can be directly placed in the gas cuvette holder in most of the UV spectrophotometers available. The construction material is filled PTFE, which is an electrically conductive material. By applying a voltage over the whole instrument the gas flow cell, including the gas chromatograph with its injector, can be heated to a stable temperature. The gas-chromatographic column is 80 mm long and, in order to get a sufficient plate number, ordinary HPLC packing materials are used. The best results have been obtained by using Nucleosil CI8 (10 pm) as the support and didecyl phthalate as the liquid loading at about 4% mlm; for an 80-mm column about 1000 theoretical plates are obtained. UV spectral scanning of compounds is obtained by interrupting the gas glow when the separated compound is in position in the light beam.