Supercritical fluid extraction/gas chromatography with thermal desorption modulator interface and nitro‐specific detection for the analysis of explosives

Abstract

Abstract. Supercritical fluid extraction (SFE) can greatly reduce the sample preparation time of analytes in solid matrices. The on-line coupling of SFE with high-speed gas chromatography (GC) can further reduce the total analysis time. SFE has been coupled to GC with a thermal desorption modulator (TDM) interface. A thermal energy analyzer (TEA), a chemiluminescence detector which is specific for nitro and nitroso compounds, has been coupled to the system to analyze explosives in soil samples.The use of organic modifiers to increase the solvation power of carbon dioxide was necessary for the extraction of various explosives, and did not adversely affect the performance of the system. Thermally labile compounds, however, such as the nitrate esters, were shown to decompose in the modulator before the chromatographic separation.This method allows for the rapid analysis of relatively volatile and thermally stable nitro compounds from solid matrices. The system can be used for screening small samples in short periods of time. Total analysis can be completed in less than 10 minutes and requires only 200 mg of soil. The minimum detectable quantity for the analysis of 2,4-DNT was found to be 2.6 ppb in an actual soil sample.

Supercritical Fluid Chromatography and Extraction

“…The key to combining SFE with chromatographic methods is the interface between the techniques. Francis et al used a thermally modulated interface approach for the SFE-GC determination of explosives with detection with a thermal energy analyzer (372). Detection in SFE-GC systems was also evaluated by Farnsworth et al who used a two-channel optical device to enhance the selectivity of sulfur detection with a radiofrequency plasma detector (373).…”

Chemiluminescence detection systems for the analysis of explosives

“…TEA has also been used by Francis et al [22] as a detection method in chromatography combined with supercritical fluid extraction (SFE) to analyze explosives in soil samples. The authors report that the coupling of SFE and GC with a thermal desorption modulator (TDM) interface allows the rapid analysis (10 min) of relatively volatile and thermally stable nitro compounds from solid matrices and it can be used for screening small samples in short periods of times.…”

Ion spectrometric detection technologies for ultra‐traces of explosives: A review

“…SFE is a potential extraction method for various explosives: air samples containing TNT, DNT and dinitrobenzene (DNB) in ng concentrations have been successfully detected by HPLC (Batlle et al, 2002) and GC using SFE as an on-line extraction method. SFE/GC with organic modifiers has been used to analyze explosives from solid matrices (Francis et al, 1995) Improved selectivity and sensitivity were obtained using a hyphenated technique including SFE and SFC: this method facilitates the analysis of explosive materials at pg levels. The separation of explosives prior to MS analysis with SFC has been demonstrated (McAvoy et al, 1999).…”