Electrochemical Determination of N-Guanylurea Dinitramide (FOX-12) Using a Poly(Methyl Orange)-Modified Carbon Nanotube Electrode

This study introduces a novel electrochemical method and a sensor electrode designed for the first time to enable the selective and sensitive quantification of N-guanylurea dinitramide (FOX-12) via square-wave voltammetry (SWV). A glassy carbon (GC) electrode was surface-modified to create the new working electrode using poly-(methyl orange: MO), which was altered by electropolymerizing the acid/base indicator MO using cyclic voltammetry and dripping well-dispersed multiwalled carbon nanotubes solution onto the electrode surface. The current intensity was correlated to the concentration of FOX-12, and the calibration line was built between 10 and 100 mg L^-1 of FOX-12. The limit of detection (LOD) and the limit of quantitation (LOQ) for FOX-12 were 1.5 mg L^-1 and 5.0 mg L^-1, respectively, and its distinctive reduction peak potential was determined to be around -1.25 V. Additionally, the modified GC/MWCNTs/pMO electrode was effectively used to measure FOX-12 in the presence of synthetic and real mixtures of energetic substances. Furthermore, FOX-12 (50 mg L^-1) was quantitatively recovered at 40-fold concentrations of common soil ions and 10-fold concentrations of camouflage materials. The proposed method was applied to clay soil samples polluted with FOX-12 and validated against an HPLC method using the statistical <i>t</i>- and <i>F</i>-tests.