Monocrystalline Diamond Paste-Based Electrodes and Their Applications for the Determination of Fe(II) in Vitamins

A new class of electrochemical sensors, namely, electrodes based on diamond paste, was designed using monocrystalline diamond (natural diamond 1 (mu)m and synthetic diamond, 50 (mu)m (synthetic-1) and 1 (mu)m (synthetic2)) powder and paraffin oil. The characterization of the electrodes was performed using cyclic voltammetry and differential pulse voltammetry. Fe(II) was determined by differential pulse voltammetry (DPV) at 75 mV (vs Ag/AgCl) using all diamond paste-based electrodes. The linear concentration range was between 10-8 and 10-4 mol/L for both the natural diamond and synthetic-2 with detection limits of 10-10 and 10-9 mol/L, respectively, whereas the linear concentration range for synthetic-1 was between 10-7 and 10-3 mol/L with a detection limit of 10-8 mol/L. Fe(II) was determined successfully from four types of pharmaceutical products. The recovery values of Fe(II) in the pharmaceutical products were higher than 98.00% with relative standard deviation values <5%.