A simple electroanalytical procedure for the determination of calcium in biodiesel

Voltammograms showing the qualitative reactivity for the Ca-EDTA system in pH 9.4 (ammonium buffer 0.01 mol L−1) on the glassy carbon electrode surface (υ = 100 mV/s; (a) bare electrode; (b) 4 × 10−3 mol L−1EDTA on the CGE; (c) = (b) after addition of 1 × 10−4 mol L−1 Ca2+.