Reusable doped sol-gel graphite electrodes for metal ions determination

A reusable sol-gel graphite composite electrode for the determination of Fe (II) in aqueous solutions is presented. This sensor was prepared by mixing a sol-gel precursor (e.g., methylhimethoxysilane) and graphite powder, prev iously modified with 4,7-dimethyl-1,10-phenanthroline. Fe(II) uptake was do ne by immersing the electrode in Fe(II) solutions at pH 2, TFA/NaOH, for 5 min. The complexation of Fe(II) was followed by Osteryoung square wave volt ammetry. Variables affecting the electrode response such as the chemical na ture of the ligand and sol-gel precursor, the HCl and ethanol concentration s, added organics and pretreating and renewing of the electrode surface wer e investigated. This sensor can measure Fe(II) with a linear range from 1.0 x 10(-5) M to 5.0 x 10(-4) M, a sensitivity of 4.80 A/M cm(2) and a detect ion limit of 7.0 x 10(-6) M. These results were not affected by the presenc e of a 100-fold amount times of Co(II), Ni(II), Mn(II), Cu(I), Cu(II) and A g(I). Determination of Fe(II) in peach leaves with this electrode gave a va lue of 210 +/- 11 mu g/g compared to an accepted value of 218 +/- 14 mu g/g and with a 3.7% relative error. The generality of this approach to the mea surement of other metal ions like Ni(II) and Cu(I) is also demonstrated. Im portant advantages of this electrode are its simple fabrication, easy renew ability, reproducible analytical results and good stability.