Comparison of plain and indoline modified mercury film electrodes for determination of lead, cadmium and copper in urine samples by anodic stripping voltammetry

The objective of this work is to assess response characteristics of conventional mercury film (MFE) and (poly)indoline modified mercury film electrodes (ICMFE) in determination of Cu, Pb and Cd ions by voltammetric stripping analysis. Parameters regarding to mercury and polymer film formations (such as potential, electrochemical mode chosen for film growth, polymer and mercury film thicknesses) and supporting electrolyte type and pH in stripping analysis were thoroughly studied, and conditions providing the highest and most stable responses for the three test metal ions were determined for both electrode types. Performances of the electrodes were evaluated in terms of sensitivity and selectivity in both synthetic aqueous solutions and urine samples. Responses at ICMFE were invariably much lower compared to that obtained at plain MFE. Decomposition of urine samples by hot mineral acid gave rise to enhanced responses at both electrodes. However, ICMFE always exhibited negative selectivity toward Cd even in acid decomposed urine samples. Reliability of the concentration values calculated by the method of standard addition in complex matrices, such as urine, was discussed comprehensively on statistical basis.