Boosted sensing performance of picric acid explosive in wastewater and soil samples using disposable carbon electrodes immobilized with thiophenecarboxaldehyde and gold clusters

A cost-effective, easily fabricated, disposable, and highly selective electrochemical platform was fabricated for the sensitive detection of hazardous explosive picric acid in real samples. This innovative electrode was constructed by immobilizing multi-walled carbon nanotubes, gold clusters, and thiophenecarboxaldehyde onto a graphite surface. Comprehensive characterization of the manufactured sensor was carried out using cyclic voltammetry, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy techniques. The proposed electrode exhibited remarkable analytical performance, achieving a high calibration sensitivity of $26.44\mathrm{\mu A}.L.{\mathrm{mg}}^{-1}.{\mathrm{cm}}^{-2}$, an exceptionally low detection limit of 12 μg/L, and broad linear ranges of 25–400 μg/L and 1–16 mg/L. The fabricated electrode exhibited a 297 % increase in current compared to the bare electrode. This enhancement was attributed to mechanisms analogous to the Henry reaction and acid-base interactions. In addition, the sensor demonstrated excellent repeatability and reproducibility (relative standard deviation (RSD) <5 %) along with impressive stability, maintaining 97.3 % of its signal after seven days. To ensure accuracy, the proposed method was validated using Elements in Soil (UME EnvCRM 03) and Elements in Wastewater (UME CRM 1204) certified reference materials, yielding recovery rates between 96.88 % and 103.56 % and RSD values lower than 4.50 %. These results confirm the high reliability and accuracy of the developed sensor and the analytical method.