Chromatographic detection of nitroaromatic and nitramine compounds by electrochemical reduction combined with photoluminescence following electron transfer
Sj. Woltman et al., Chromatographic detection of nitroaromatic and nitramine compounds by electrochemical reduction combined with photoluminescence following electron transfer, ANALYT CHEM, 72(20), 2000, pp. 4928-4933
The oxidizing agent tris(bipyridyl)ruthenium(II), or Ru(bpy)(3)(3+), is use
d as a postcolumn reagent for the detection of nitroaromatic and nitramine
explosive compounds. After separation, the explosives are reduced electroch
emically to oxidizable products such as hydroxlamines and nitrosamines, and
these products react readily with Ru(bpy)(3)(3+) and RU(bpy)(3)(2+). The p
hotolumininescence from the latter is used far detection. A porous carbon e
lectrode was used for on-line analyte reduction following chromatography. A
nother porous carbon electrode was used to generate the nonluminescent RU(b
py)(3)(3+) from Ru(bpy)(3)(3+) on-line at high efficiency. The two streams
were combined, and the Ru(bpy)(3)(2+) produced by oxidation of the reduced
analytes was detected by laser illumination and light detection, Reductive
hydrodynamic voltammograms of nitrobenzene, 2,4,6-trinitotoluene, and hexah
ydro-1,3,5-trinitro-1,3,5-triazine indicated that a potential of -1500 mV v
s Ag/AgCl was sufficient to achieve a maximum signal from the reduced analy
tes. HPLC with a water/acetonitrile gradient on a C-18 reversed-phase colum
n was then used to determine these three compounds plus the four additional
examples, 1,3,5,7-tetrazocine, 2,4-dinitrotoluene; 2,6-dinitrotoluene, and
4-nitrotoluene, For both hydrodynamic voltammetry and HPLC detection, the
photoluminescence following electron-transfer signal was calibrated using t
he one-electron standards ferrocene and ferrocenecarboxylic acid. Detection
limits were in the low-nanomolar range for 20-mu L injections of nonprecon
centrated nitro compounds.