Sensitive analytical detection of nitrite using an electrochemical sensor with STAB-functionalized Nb₂C@MWCNTs for...

An electrochemical sensor based on stearyl trimethyl ammonium bromide - functionalized niobium carbide@multi-walled carbon nanotubes (Nb₂C@MWCNTs-STAB) for signal amplification was successfully constructed for sensitive detection of nitrite (NO₂^-). Niobium carbide@multi-walled carbon nanotubes (Nb₂C@MWCNTs) with high electrical conductivity and water dispersibility were first prepared in a one-pot hydrothermal synthesis, after which cationic STAB was added to overcome the negative surface charge on the Nb₂C@MWCNTs. The electrostatic attraction between Nb₂C@MWCNTs-STAB and NO₂^- was improved by the STAB, which enhanced the sensitivity of the constructed sensor for NO₂^-. Under optimized conditions, Nb₂C@MWCNTs-STAB/GCE exhibited excellent analytical performance for detection NO₂^- with two wide liner ranges (0.1-100 μmol L^-1 and 100-2000 μmol L^-1) and a limit of detection of 0.022 μmol L^-1. Nitrite recovery tests in milk and spinach samples showed recoveries in the range of 89.82-104.52%. The NO₂^- residues in ham and pickled vegetable (cedrela sinensis) samples were analysed using the presented sensor and a spectrophotometric method, with no significant difference found between the results of the two methods.