Stripping voltammetric analysis of cadmium on a dual working screen-printed carbon electrode modified with graphene-oxide/carbon-nanohorn composite

• Differential SV on 2WEs-SPCE decouples pre-concentration and measurement. • 1:1 GO/CNH coating enhances Cd²⁺ adsorption and electron-transfer kinetics. • Dual linear ranges (20–300 / 300–1000 µg L⁻¹) with 4.6 µg L⁻¹ detection limit. • Background-subtracted signal shows < 10 % interference from common ions. • Disposable, low-cost chip accurately quantifies Cd²⁺ in tap and lake water samples. . Accurate field monitoring of cadmium is hindered by electrode fouling and matrix interferences that plague conventional stripping voltammetry (SV). Here we introduce a differential-SV strategy that pairs two screen-printed working electrodes on the same chip (2WEs-SPCE) to decouple pre-concentration from signal read-out. The first electrode (WE1) accumulates Cd 2+ , while the second (WE2) records a background-free, non- pre-concentrated trace; subtracting the two currents suppresses drift and eliminates false positives. Both surfaces are nanostructured with a 1:1 graphene-oxide/carbon-nanohorn (GO/CNH) film that combines GO’s affinity for heavy metals with CNH’s high conductivity, boosting adsorption kinetics and signal stability. The sensor delivers dual linear ranges, 20-300 µg. L −1 (R 2 = 0.994; 0.0415 µA. µg −1 . L) and 300-1000 µg. L −1 (R 2 = 0.986; 0.0241 µA. µg −1 . L), with limit of detection and limit of quantification of 4.6 and 15.20 µg. L −1 , respectively, appropriate for qualification of Cd 2+ contamination in water sample. This differential 2WEs-SPCE platform marries low-cost printing with nanocarbon synergy, delivering interference-resistant, ppb-level cadmium sensing that is ready for on-site environmental and food-safety deployment. .