Simple and direct potentiometric determination of potassium ions in biodiesel microemulsions at a glassy carbon electrode modified with nickel(II) hexacyanoferrate nanoparticles

Considering the great importance of the determination of inorganic ions present in fuels, particularly in relation to potassium, the scope of this work was to develop a potentiometric method using a chemically modified electrode with nanoparticles of nickel hexacyanoferrate for the determination of potassium ions in a microemulsion of biodiesel. The electrochemical studies showed the possibility of electrochemical measurements in biodiesel microemulsion and the good stability of the modified electrode in this medium. The modified electrodes (surface excess of 16.1 +/- 1.6 nmol cm(-2)) in a microemulsion composed of biodiesel : propan-1-ol : aqueous phase (5 : 70 : 25 in volume) exhibited a detection limit for potassium ions of 5.3 x 10(-5) mol L-1 and a slope of 58 mV, with a linear response in the concentration range of 5.0 x 10(-5) mol L-1 to 1.0 x 10(-2) mol L-1. The recoveries obtained were between 91 and 106%. Thus, the proposed method using the preparation of a microemulsion of the samples proved to be an efficient method for the determination of potassium in biodiesel.