Selective determination of 2,4,6-Trinitrotoluene (TNT) with cysteamine in deep eutectic solvents

Abstract

2,4,6-trinitrotoluene (TNT) is one of the most widely used explosives for military and civilian purposes. Detection of TNT is very important for both human health and public safety. In this study, TNT determination was carried out using a new solvent medium containing cysteamine (CysN) without the need for noble metal nanoparticles (i.e. CysN-AuNPs used for anchoring CysN through S-atom) or strong alkalinity (i.e. to stabilize TNT-Meisenheimer anions in aqueous medium). CysN was prepared in a deep eutectic solvent (DES) consisting of a mixture of choline chloride and ethylene glycol, and the color of the Meisenheimer complex was derived from the donor–acceptor interaction between the amine group on CysN and the nitro group on TNT. The Lewis base-acid neutralization product, CysN-TNT charge-transfer complex, was stable in the optimized DES solvent unlike that in water. The absorbance of the resulting red complex was measured at 515 nm. The LOD and LOQ values were found to be 67.17 and 223.90 μg L− 1, respectively. The proposed method was not affected by similar explosives, camouflage agents, and possible ion interference in the soil. Finally, the method was validated with an HPLC-DAD analysis. This method is the first study to use DESs in the determination of energetic materials such as TNT and the proposed assay shows excellent selectivity for TNT. The proposed method stands out as it is fast, simple, of low cost, compatible with green chemistry with the potential to convert to a paper-based colorimetric sensor.