What method is employed for measuring iron or lead by plating and oxidizing it?

The method used for measuring iron or lead by plating and subsequently oxidizing it is anodic stripping voltammetry. This technique involves the deposition or plating of the ions onto the working electrode surface, followed by a potential sweep that oxidizes these plated metals back into their ionic forms. The current produced during the oxidation process is proportional to the concentration of the metal ions present in the sample, allowing for sensitive detection and quantification.

Anodic stripping voltammetry is particularly valuable for trace metal analysis due to its high sensitivity and ability to analyze metals at very low concentrations. The process involves two main steps: the accumulation phase, where metal ions are reduced and deposited onto the electrode surface, and the stripping phase, where the potential is reversed to oxidize the deposited metals. This combination of reduction and oxidation allows for precise measurements of the target metal.

In contrast, other methods like polarography and amperometry do not employ the same plating technique for measurement, while coulometry involves measuring the total electric charge required to completely convert the analyte to a product, which doesn't neatly fit the assessment of metals through plating followed by oxidation. Thus, anodic stripping voltammetry is the correct and most appropriate method for measuring iron or lead in this context.