Cathodic Stripping Analysis Complicated by Adsorption Processes: Determination of 2-Thiouracil at a Rotating Silver Disk Electrode.

摘要

A new method of interpretation of cathodic stripping peak current data is proposed where slow adsorption/desorption of the solution species to be determined is involved. Mechanisms of processes taking place during deposition and stripping steps which are complicated by adsorption/desorption are considered. As an example of such a system, the electrodeposition and stripping of a 2-thiouracil silver compound at the rotating silver disk electrode have been investigated at physiological pH = 7.2. Two concentration regions for the determination of 2-thiouracil, which appear in nature as a pyrimidine base of nucleic acid, have been found. The first region involves microphase deposition which occurs if the total charge passed through the electrode during cathodic stripping of the most easily removed material is less than 70 micro c/sq cm. The second region, for charges greater than 200 micro c/sq cm, corresponds to macrophase stripping. The effect of concentration, potential sweep rate, rotation speed, deposition potential and other parameters on the shape and height of the stripping peaks have been determined. The lowest concentration of 2-thiouracil determined was 6 x 10 to the -8th power mol/cu m.