Determination of phosphate ions in aqueous solutions attracts a great deal of interest in the areas of environment, medicine, and agriculture. As phosphoric acid is a poly basic acid, the different forms of existence at different pH result in direct determination facing a big challenge. Herein, we reported a potentiometric phosphate ion sensor based on a surface-modified tungsten electrode. Pure tungsten was electrodeposited at a constant potential of 0.2 V versus Ag|AgCl in Na₂HPO₄. WO₃ and H₃O₄₀PW₁₂·xH₂O were electrodeposited on the surface of the tungsten electrode. The modified tungsten electrode was used as a working electrode in a two-electrode system to detect the concentration of phosphate ions in aqueous solutions. The detection limit of the modified tungsten electrode for phosphate ions is 10^–6 M from pH 7 to pH 8 and 10^–5 M from pH 9 to pH 10. It has good selectivity to other common anions. The long-term monitoring experiment showed that the potential fluctuation was less than ±3 mV in 24 h. Compared to conventional determination methods, the current phosphate ion sensor showed a close value in a real sample. The mechanism of phosphate ion response was investigated in detail. This sensor possesses advantages of simple manufacture, low cost, a wide pH range for detecting, and good selectivity.

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pH is an important chemical index. The measurement of pH is widely used in various fields. At present, the most common pH meter on the market is the glass electrode pH meter, which has many advantages, such as high accuracy, short response time and so on. However, when industrial wastewater and environmental water samples need long-time real-time monitoring, such as using glass electrode pH meter will lead to leakage of internal liquid, fragile glass and sodium difference. Therefore, it is urgent to design and develop a new type of pH meter with all solid, simple structure and no nanodeviation. In this study, an all solid state electrochemical modified pH electrode was developed based on the adsorption and storage of hydrogen by niobium. Hydrogen in hydrochloric acid was adsorbed and stored in niobium electrode by constant potential electrolysis. The results showed that the detection linear range was pH1-pH13, the response slope was −56.4 mV dec ⁻¹ , and the response time was 5 seconds. In the actual sample detection, the detection results are consistent with the glass electrode pH meter. In addition, cyclic voltammetry and electron microscopy were used to study the response mechanism.