Selective spectrophotometric determination of TNT in soil and water with dicyclohexylamine extraction

• Published in: Analytica Chimica Acta
• Main Authors: Apak, R, Uzer, AE, Ercag, Erol
• Other Authors: ,, 23480
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2005
• Subjects: Analitik Kimya; Temel Bilimler (SCI); Kimya; KİMYA; ANALİTİK; Temel Bilimler; Cold Regions Research and Engineering Laboratory
• Online Access: https://hdl.handle.net/20.500.12627/62365; https://doi.org/10.1016/j.aca.2004.11.045

Contaminated land and groundwater remediation in military waste dumping sites often necessitates the use of simple, cost-effective, and rapid tests for detecting trinitrotoluene (TNT) residues in the field along with their dinitro-analogues. A simple, rapid, low-cost, and field-adaptable (on-site) colorimetric method was developed for quantifying TNT in the presence of RDX, PETN, picric acid, 2,4-DNT (dinitrotoluene), dinitrophenol, and dinitroaniline. Most commercialized methods for TNT assay-with the exception of Cold Regions Research and Engineering Laboratory of the U.S. Army (CRREL) method-use proprietary chemicals, and the color stability and intensity are highly dependent on the composition of the organic solution comprised of acetone or methanol. The developed colorimetric method is based on the extraction of TNT from water-acetone solution into an organic solvent mixture of dicyclohexylamine (DCHA)-isobutyl methyl ketone (IBMK) (10: 1, v/v), filtration through a filter paper into a stoppered optical cell containing anhydrous sodium sulfate, and measurement of the absorbance of the organic extract at 531 nm after 5 min. The red-violet color of the extract was due to intermolecular charge-transfer (CT) between the electron attracting TNT and electron-donating DCHA, and the molar absorptivity for TNT in final organic solution was (1.16 +/- 0.02) x 10(4) L mol(-1) cm(-1).The R.S.D. of the slope of calibration line was 0.7%. The LOD of the method in the final organic phase was 0.38 mu M TNT, and LOD values expressed on the basis of original soil TNT content were 0.5, 1.3, and 1.5 ppm (mu g g(-1)) for clay, loamy clay, and sandy soils, respectively. Unlike other spectrophotometric methods, the developed assay was basically tolerant to common cations and anions found in soil and water at 100-fold weight ratios, and to soil humic acids. Among a number of compounds that may be encountered in polynitro-explosive storage and waste reclaimation sites such as picric acid, dinitrophenol, 2,4-dinitrotoluene. ...