In the amperometric titration method for chlorine, what is the titrant that is used?

In the amperometric titration method for measuring chlorine levels in water, Phenylarsine Oxide (PAO) is the titrant used. This method operates on the principle of measuring electric current in response to the concentration of chlorine in the sample. When PAO is added as a titrant, it reacts specifically with the chlorine present in the sample. The reaction leads to a reduction of the chlorine level, and the change in the current measured by the amperometric sensor provides information about the concentration of chlorine that was present.

This specific choice of PAO as a titrant is essential because it facilitates a precise and accurate measurement of chlorine levels, which is critical for ensuring that water meets safety standards. Other substances, like sodium hydroxide, ferrous ammonium sulfate, and hydrochloric acid, do not have the same direct reaction with chlorine that would allow for the specific amperometric measurement needed in this context. Therefore, PAO is the appropriate and effective choice in the amperometric titration method for chlorine analysis.