SPME-HPLC Methodology for Detection of Nitroexplosives

Solid phase microextraction (SPME) has been coupled with liquid chromatography to widen its range of application to nonvolatile and thermally unstable compounds, generally limited for SPME-GC. A method for analysis of nitroaromatic explosives and its degradations products was developed using SPME and high performance liquid chromatography with ultraviolet detection (HPLC/UV), introducing a modified interface that ensure accuracy, precision, repeatability, high efficiency, unique selectivity and high sensitive to detection and quantification of explosives from surface soil samples and increased chromatographic efficiency. A pretreatment step was introduced for the soil samples which extracted the target compounds into an aqueous phase. Several parameters that affect the microextraction were evaluated, such as: fiber coating, adsorption and desorption time, desorption mode, stirring rate, the effect of NaCl (salting out) concentration on analyte extraction and the role of various solvents on SPME fiber. Carbowax-templated resin (CW/TPR) and Polydimethilsiloxane-divinilbenzene (PDMS-DVB) fibers were used to extract the analytes from the aqueous samples. Explosives were detected at 330 pg concentrations. Effects of daylight and UV radiation were analyzed over soil samples during 1 month and degradations products found were: 1,3,5-TNB, 1,3-DNB, 2,4-DNT, 2,6-DNT, 4-Nitrotoluene and 3-Nitrotoluene. This study demonstrates that SPME-HPLC is a very promising method of analysis of explosives from soils and aqueous samples and has been successfully applied to the determination of nitroaromatic compounds, such as TNT.

Keywords: SPME, HPLC-UV, nitroexplosives, absorption fibers, TNT