A novel phosphomolybdic acid–polypyrrole/graphene composite modified electrode for sensitive determination of folic acid

• A novel PMo12–PPy/GR composite modified electrode is fabricated.
• FA exhibits excellent inhibition toward the redox of PMo12 on the PMo12–PPy/GR/GCE.
• GR and PPy have synergistic effect on PMo12 for sensitive determination of FA.

A novel phosphomolybdic acid–polypyrrole/graphene composite modified glassy carbon electrode has been fabricated for the sensitive determination of folic acid based on the inhibitory activity of folic acid towards the redox behavior of Keggin-type phosphomolybdic acid. The redox behavior of the modified glassy carbon electrode is investigated by cyclic voltammetry and the electrochemical behavior of folic acid is studied by differential pulse voltammetry. From this study, it is found that on the modified electrode the redox process of phosphomolybdic acid is surface-controlled, which can form a much stronger complex with folic acid than H+ in 0.01 M H2SO4. The reduced peak current of phosphomolybdic acid has a good linear relationship with FA concentration in the range from 1.0 × 10−9 to 2.0 × 10−7 M, and the detection limit of FA is calculated to be 3.3 × 10−11 M.