The Trace Analysis for Explosives and Related Compounds Via High Performance Liquid Chromatography-Photolysis-Electrochemical Detection

Abstract

Organic nitro compounds, such as explosives, are amenable to high performance liquid chromatographic (HPLC) analysis with a variety of appropriate, selective or general, detectors. Although such compounds have been studied recently by electrochemical detection (EC) in the reductive mode, virtually nothing has been reported on the application of oxidative EC for such compounds. Since the parent compounds themselves cannot be electrochemically oxidized, nitrite (NO₂⁻) released post-column, on-line, in real time, by photolysis of the HPLC effluent, can very readily be detected at trace levels by oxidative EC methods and techniques. A wide variety of organic nitrate esters (R-O-NO₂), N-nitro (N-NO₂) nitramine derivatives, as well as aliphatic/aromatic C-nitro (C-NO₂) compounds, can all be analyzed at trace levels by this HPLC-photolysis-EC (HPLC-hv-EC) approach. A large number of explosives and certain drugs have been studied by these approaches. The basic high performance liquid chromatography-photolysis-electrochemical detection (HPLC-hv-EC) system has been optimized with regard to minimum detection limits (MDLs), linearity of responses as a function of concentration/amounts injected, specific HPLC separations and mobile phases compatible with hv-EC derivatization-detection, dual detector EC response ratios for individual analytes, and other suitable analytical parameters of importance and interest. Some applications of this method to real world samples of explosive debris are also described.