In this study, we successfully developed a solid-state reference electrode based on sodium polyanethol sulfonate (SPS) immobilised on a cellulose acetate membrane and coated on a layer of polypyrrole on top of a carbon screen-printed electrode (SPE). We varied the concentration of SPS salt from 1% to 5% (w/v) and achieved an optimal concentration of 4%. SPS optimisation test was performed by varying concentrations of KCl and pH buffer solution. The slope obtained for 4% SPS was 3.5 ± 0.3 with a residual standard deviation (RSD) of 9.3% of KCl solution, whereas the slope obtained for pH buffer solution was 3.4 ± 0.2 with 1.2% RSD. The stability test in pH 7 buffer and 10−3 M KCl yielded drift at <0.4 mV/h for 60 h of continuous monitoring. We also performed tests using standard NH4+, K+ and NO3− ion-selective electrode sensors, and the slopes measured were respectively 52.4 ± 0.4, 51.4 ± 0.4, and −52.3 ± 0.9 mV/dec with a dynamic range of 0.1–10−5 M.