A novel electrochemical sensor for nitroguanidine determination using a glassy carbon electrode modified with multi-walled carbon nanotubes and polyvinylpyrrolidone

A novel electrochemical method for the determination of nitroguanidine (NG) was developed by modifying a glassy carbon electrode surface with a mixture of well-dispersed multi-walled carbon nanotubes (MWCNTs) and polyvinylpyrrolidone (PVP) used as a hydrogen-bonding substrate for the analyte. This sensitive and selective square wave voltammetric (SWV) method was applied in a mixture of acetonitrile and the 0.1 mol L-1 pH 7 phosphate buffer (1 : 9; v : v). The characteristic reduction potential of NG was obtained at about -1.32 V, at which the current was recorded against concentration to build the SWV calibration curves within the range of 3-100 mg L-1 of NG. The limit of detection (LOD) and limit of quantification (LOQ) were 0.6 mg L-1 and 2.0 mg L-1, respectively. NG determination was efficiently carried out in the presence of synthetic and real energetic material mixtures using the prepared GC/PVP/MWCNTs modified electrode to obtain high recoveries. Additionally, NG (10 mg L-1) was determined with quantitative recovery in the presence of 100-fold concentration (except 5-fold for Fe3+ and Cu2+) levels of potentially interferent soil ions (Cl-, CO32-, SO42-, NO3-, Na+, K+, NH4+, Mg2+, Ca2+, Pb2+, Fe3+ and Cu2+) and of some electroactive substances used as camouflage materials having a similar color and appearance to explosives (paracetamol, caffeine (6-fold), acetylsalicylic acid, aspartame, d-glucose and detergent). The proposed SWV method was also applied to NG-contaminated clay soil samples, and statistically validated against LC-MS using Student t- and F-tests.