All-Solid-State Potentiometric Sensor Based on Graphene Oxide as Ion-to-Electron Transducer for Nitrate Detection in Water Samples

Abstract

Graphene oxide (GO) was used as an ion-to-electron transducer for all-solid-state nitrate electrodes based on an alkyl ammonium salt as the sensing element. Commercially available carbon screen-printed electrodes modified with GO were used as conductive substrates, whose morphology and distribution along the surface were evaluated by scanning electron microscopy and Raman spectroscopy. The potentiometric performance of the GO-based electrodes revealed a Nernstian slope of −53.5 ± 2.0 mV decade−1 (R2 = 0.9976 ± 0.0015) in the range from 3.0 × 10−6 to 10−2 M and a lower limit of detection of 1.9 × 10−6 M. An impressive reproducibility between equally prepared electrodes (n = 15) was demonstrated by a variation of −1, and a stable performance (LOD and sensitivity) over 3 months. The applicability of the proposed sensors was demonstrated in determining nitrate levels in water samples with great accuracy, yielding recovery values from 87.8 to 107.9%, and comparable (p > 0.05) results to a commercial nitrate probe. These findings demonstrate the use of GO as an alternative ion-to-electron transducer for the fabrication of all-solid-state potentiometric electrodes.

Keywords

• graphene oxide
• ion-selective electrodes
• potentiometry
• nitrate
• water