SUPERCRITICAL-FLUID EXTRACTION GAS-CHROMATOGRAPHY WITH THERMAL-DESORPTION MODULATOR INTERFACE AND NITRO-SPECIFIC DETECTION FOR THE ANALYSIS OF EXPLOSIVES

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.