Development of electrokinetic capillary electrophoresis equipped with amperometric detection for analysis of explosive compounds

Cyclic voltammograms of trinitrotoluene (TNT) and other related explosive c ompounds obtained by using glassy carbon, platinum, nickel, gold, and silve r electrodes revealed the applicability of gold and silver in capillary ele ctrophoresis (CE) amperometric detection. The selected electrode, gold or s ilver, was inserted into a specially designed detection cell that was easil y adapted to a commercial CE apparatus. The electrochemical reduction of TN T, octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), hexahydro-1,3,5- trinitro-1,3,5-triazine (RDX), and 10 other explosives could be reliably mo nitored at -700 mV vs Ag/AgCl. CE analyses were performed with a berate buf fer(15 mM, pH 8.7) containing 25 mM sodium dodecyl sulfate (SDS) to attain baseline resolution of the selected compounds. A bimetal electrode, prepare d by depositing silver on gold, offered a superior performance by exploitin g the sensitivity of gold while suppressing its response toward acetonitril e to achieve a 10-fold lower detection limit than UV measurement. The CE sy stem equipped with amperometric detection was used to determine the explosi ve content of soil extracts and groundwater, yielding results in good agree ment with those obtained by the liquid chromatographic method recommended b y the U.S. Environmental Protection Agency.