A Novel ultrasensitive nitrite ion detection using tungsten trioxide-modified gold electrode

A novel ultrasensitive nitrite ion detection using tungsten trioxide/carbon (WO₃/C) modified gold electrode has been studied. The WO₃ was synthesized from tungsten metal through chemical methods with selective precipitation techniques. The visual color of the material obtained is bright yellow, indicating WO₃ compound. The X-ray diffraction (XRD) diffractogram confirms WO₃ compound in monoclinic shaped by showing of the 2θ at 23.205, 23.723, 24.384, 33.426, and 33.911. The characterization using Field Emission Scanning Electron Microscopy (FESEM) showed that the material obtained was a disk-shaped with diameter 150–250 nm and a thickness of 50 nm. The Energy Dispersive X-ray spectroscopy (EDX) also confirms WO₃ compound with no impurities. The gold electrode was modified by dip immersion technique where the gold electrode was dipped in a mixture of WO₃-carbon paste. The measurement of surface area by cyclic voltammetry shows that the WO₃/C modified gold electrode has the highest surface area compared to unmodified gold and C-modified gold electrode, indicating it has more active electron transfer sites. The WO₃/C modified gold electrode worked well at pH 7 for the detection of nitrite ion and gave the highest peak current (0.875 V) than the others. The measurement ranges from 1–200 mg/L with no interference from ${\text{NO}}_3^{-}$, ${\text{SO}}_4^{2-}$, $Z{n}^{2+}$, $F{e}^{2+}$, $P{b}^{2+}$, $C{l}^{-}$, $C{a}^{2+}$, and ${\text{NH}}_4^{+}$ ions. The sensitivity and the LOD of the electrode are 8.86 μA.L.mg⁻¹.cm⁻² and 0.8 µg/L, respectively. The proposed method not only exhibits identical precision and accuracy to the standard method in detecting nitrite ions in real samples but also offers the advantages of rapid analysis, uncomplicated pretreatment procedures, environmental friendliness, and economical operation. This performance indicates that the WO₃/C modified gold electrode is feasible as an alternative electrode for nitrite ion detection.