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

Abstract

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.