A Sensitive Simultaneous Determination of Epinephrine and Tyrosine using an Iron(III) Doped Zeolite-Modified Carbon Paste Electrode

A Zeolite modified carbon paste electrode doped with iron(III) was used as a highly sensitive and selective electrochemical sensor for simultaneous determination of minor amounts of epinephrine (Ep) and tyrosine (Tyr) as the biologically important compounds. The results of differential pulse voltammetry (DPV) using this modified electrode show two well-resolved anodic waves for the oxidation of Ep and Tyr, which makes it possible for simultaneous determination of both compounds. A linear range from 0.9 to 216 mu mol L-1 for Ep at a constant concentration of 30 mu mol L-1 Tyr in buffered solution (phosphate buffer, pH 3.0) was obtained from DPV measurement using this electrode with a correlation coefficient of 0.9998 and a detection limit of 0.44 mu mol L-1. The linear range, which is obtained for Tyr in the presence of 30 mu mol L-1 Ep, was in the range from 1.2 to 90 mu mol L-1 with a correlation coefficient of 0.9989 and a detection limit of 0.32 mu mol L-1. The modified electrode had good reproducibility (RSD < 2.5%), low detection limit (sub-micromolar) and high sensitivity for the detection of both Ep and Tyr with a very high stability in its voltammetric response. The analytical performance of this sensor has been evaluated for detection of Ep and Tyr in human serum and in a pharmaceutical sample with satisfactory results.