Simple, robust, and low-cost nitrate- and ammonium-selective electrodes were made using substrate prepared from household materials. We explored phosphonium-based ILs and poly (methyl methacrylate)/poly(decyl methacrylate)(MMA-DMA) copolymer as matrix materials alternative to classical PVC-based membranes. IL-based membranes showed suitability only for nitrate-selective electrode exhibiting linear concentration range between 5.0 × 10-6 and 2.5 × 10-3 M with a detection limit of 5.5 × 10-7 M. On the other hand, MMA-DMA-based membranes showed suitability for both ammonium- and nitrate-selective electrodes, and were successfully applied to detect NO₃- and NH₄⁺ in water and soil samples. The proposed ISEs exhibited near-Nernstian potentiometric responses to NO₃- and NH₄⁺ with the linear range concentration between 5.0 × 10-5 and 5.0 × 10-2 M (LOD = 11.3 µM) and 5.0 × 10-6 and 1.0 × 10-3 M (LOD = 1.2 µM), respectively. The power of ISEs to detect NO₃- and NH₄⁺ in water and soils was tested by comparison with traditional, portable colorimetric techniques. Procedures required for analysis by each technique from the perspective of a non-trained person (e.g., farmer) and the convenience of the use on the field are compared and contrasted.
Keywords: electrodes versus colorimetric assay; environmental analysis; ion-selective electrodes; soil analysis.