Cyclic voltammetry as a screening tool for the fungal degradation of 2,4,6-trinitrotoluene in aqueous media

ABSTRACT

The use of an electrochemical technique based on cyclic voltammetry (CV) that can be implemented to monitor the degradation of the important nitroaromatic explosive 2,4,6-trinitrotoluene (TNT) in aqueous media when in contact with a microorganism is presented. The microorganism used in this study was an isolated fungus belonging to the Aspergillus genus. In the degradation experiments, during the first 21 days of exposure of the fungal growth to a 68 mg L⁻¹ TNT aqueous stock solution, the analyte concentration decreased by 44% to 38 mg L⁻¹ before plateauing through the 58th day of the study. Statistical figures of merit of the technique included linearity in the 1–92 mg L⁻¹ range and correlation coefficients above 98% for the three reduction peaks of TNT, a limit of detection (LOD) of 3 mg L⁻¹, a limit of quantification of 10 mg L⁻¹ and a method precision of 3.8% relative standard deviation (%RSD). Day-to-day and week-to-week repeatability were low at 5.1%RSD and 5.8%RSD, respectively. The results herein exhibit first-order kinetics for the ‘ortho’ nitro group. A clear to yellow colour transition in the control solution and fungi samples suggests the appearance of a TNT metabolite. UV-Vis spectrophotometry supports the presence of a possible derivative of TNT in the fungi samples.

KEYWORDS:

• Highly energetic materials
• electrochemistry of explosives
• cyclic voltammetry
• UV-Vis spectrophotometry
• fungi
• degradation kinetics

Acknowledgements

We thank Dr. Juan Lopez-Garriga for allowing us to use his facilities to conduct UV-Vis spectrophotometric measurements. This material is based upon work supported by the US Department of Homeland Security, Science and Technology Directorate, Office of University Programs, under Grant Award 2013-ST-061-ED0001. The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the US Department of Homeland Security.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the U.S. Department of Homeland Security, Science and Technology Directorate; Office of University Programs: [Grant Number 2013-ST-061-ED0001].