Cyclic voltammetric determination of phosphate in tap water via [Omim]6Mo7O24-carbon paste electrodes

Stably retaining the water-soluble molybdate within electrodes is of great significance in phosphate analysis. This study fabricated an [Omim] 6 Mo 7 O 24 carbon paste electrode (OCPE), which was able to effectively retain molybdate in the aqueous solution. The electrochemistry of phosphate at the surface of the OCPE was studied using cyclic voltammetry (CV). The voltammograms showed three reversible redox peaks corresponding to the redox of Mo(VI/V) as well as several irreversible peaks involving the formation of hydrogen molybdenum bronze. The currents of all three reversible redox peaks linearly varied versus phosphate concentrations in 0.1 mol·L −1 H 2 SO 4 -KCl. After optimizing the mass ratio of the [Omim] 6 Mo 7 O 24 and carbon powder, peak C6 shows a wide linear range (1.0 × 10 –2 –1.0 × 10 –7  mol·L −1 ; R 2  = 0.9970) with a sensitivity of 5.3 (± 0.1) μA/μM. The limit of detection (LOD = 3 σ /s) was 8.5 × 10 –8  mol·L −1 . Interferences from common anions, silicate, and glyphosate on phosphate analysis were also investigated. The proposed sensing method was successfully applied to the determination of phosphate in tap water, whose results were verified with ion chromatography (IC).