Development and application of pyrolysis gas chromatography/mass spectrometry for the analysis of bound trinitrotoluene residues in soil.
TNT (trinitrotoluene) is a contaminant of global environmental significance, yet determining its environmental fate has posed longstanding challenges. To date, only differential extraction-based approaches have been able to determine the presence of covalently bound, reduced forms of TNT in field soils. Here, we employed thermal elution, pyrolysis, and gas chromatography/mass spectrometry (GC/MS) to distinguish between covalently bound and noncovalently bound reduced forms of TNT in soil. Model soil organic matter-based matrixes were used to develop an assay in which noncovalently bound (monomeric) aminodinitrotoluene (ADNT) and diaminonitrotoluene (DANT) were desorbed from the matrix and analyzed at a lower temperature than covalently bound forms of these same compounds. A thermal desorption technique, evolved gas analysis, was initially employed to differentiate between covalently bound and added 15N-labeled monomeric compounds. A refined thermal elution procedure, termed "double-shot analysis" (DSA), allowed a sample to be sequentially analyzed in two phases. In phase 1, all of an added 15N-labeled monomeric contaminant was eluted from the sample at relatively low temperature. In phase 2 during high-temperature pyrolysis, the remaining covalently bound contaminants were detected. DSA analysis of soil from the Louisiana Army Ammunition Plant (LAAP; approximately 5000 ppm TNT) revealed the presence of DANT, ADNT, and TNT. After scrutinizing the DSA data and comparing them to results from solvent-extracted and base/ acid-hydrolyzed LAAP soil, we concluded that the TNT was a noncovalently bound "carryover" from phase 1. Thus, the pyrolysis-GC/MS technique successfully defined covalently bound pools of ADNT and DANT in the field soil sample.
Weiss
Jeffrey M
JM
Department of Microbiology, Wing Hall, Cornell University, Ithaca, New York 14853, USA.
McKay
Amanda J
AJ
Derito
Christopher
C
Watanabe
Chuichi
C
Thorn
Kevin A
KA
Madsen
Eugene L
EL
D008401:Gas Chromatography-Mass Spectrometry; D017745:Incineration; D009587:Nitrogen Isotopes / Q000032:analysis; D012680:Sensitivity and Specificity; D012989:Soil Pollutants / Q000032:analysis*; D013696:Temperature; D014303:Trinitrotoluene / Q000032:analysis*
D009587:Nitrogen Isotopes; D012989:Soil Pollutants; D014303:Trinitrotoluene