Determination of explosives in soil and ground water by liquid chromatography-amperometric detection

Electrochemical reduction of trinitrotoluene (TNT) and several nitroaromatics has been exploited toward the development of an amperometric detector for liquid chromatography (LC). Up to a ten-fold increase in sensitivity was accomplished for the explosives using amperometric detection instead of conventional UV measurement. A working glassy carbon electrode (poised at -0.80 V vs. Ag/AgCl) offered a detection limit of 9, 44 and 550 nM for trinitrobenzene, TNT and 1,4-dinitrobenzene, respectively. Separation of eleven TNT-related compounds in a mixture was achieved within 15 min using a C18 column and a mobile phase consisting of acetonitrile-50 mM phosphate buffer pH 5 (1:2, v/v) and 18 mM sodium dodecylsulfate. The LC-amperometric detection system was applicable for analyzing soil extracts and ground water and the results obtained agreed well with that of the US Environmental Protection Agency recommended procedure. Extension to analysis of HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine) and RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) was accomplished with a silver working electrode instead of a glassy carbon electrode installed in a thin channel cell.