A robust and highly sensitive electrochemical probe for detection of trace levels of NH₃/NH₄⁺ in water based on Berthelot's reaction

Traditional spectrochemical methods for quantifying NH₃/NH₄⁺ based on the colored oxidation product of Berthelot or Nessler reactions, face challenges due to spectral overlap, auto-self absorbance, background scattering noise and high limits of detection. Thus, the current study introduces a new electrochemical sensing platform utilizing an ex-situ Bi film-plated glassy carbon electrode (BiF/GCE) combined with Berthelot's reaction for detecting trace levels of NH₃/NH₄⁺ in water. The primary advantage of Bi as a surface modifier of GCE is its ability to provide a selective and explicit probe for NH₃/NH₄⁺ detection at trace levels. This platform employs an ex-situ BiF/GCE, square wave-adsorptive anodic stripping voltammetry (Ads SW-ASV), and the oxidation product of Berthelot's reaction for precise indirect detection of NH₃/NH₄⁺ in aqueous solutions at pH 10–11. The probe demonstrated excellent electrochemical performance for NH₃/NH₄⁺ detection over a concentration range of 3.2 nM to 20.0 μM, with detection and quantitation limits of 0.95 and 3.2 nM, respectively. It showed good selectivity towards detection of NH₃/NH₄⁺ in water with favorable repeatability (RSD = ±3.2 %) and reproducibility (RSD = ±4.1 %). The probe's measurements were validated against standard ion chromatography (IC) and microspectrophotometry methods, demonstrating high reliability for detecting NH₃/NH₄⁺ in environmental and Red Sea water samples. This assay is precise and versatile for ammonia detection, enabling measurement of trace levels of N-containing organic compounds in foodstuffs and their degradation products.