Which instrument is commonly used for the titration of chlorine in water samples?

The amperometric titrator is commonly used for the titration of chlorine in water samples because it is specifically designed to measure the current produced by the redox reaction during the titration process. When titrating chlorine, the amperometric titrator can detect the endpoint of the reaction accurately by measuring changes in electrical current as reagents are added. This method is particularly effective for analyzing disinfectant levels such as chlorine, as it provides real-time measurements and can detect very low concentrations of chlorine.

In contrast, other instruments such as the gas chromatograph are primarily used for separating and analyzing compounds in gas phase and are not suitable for titrating aqueous samples. A fluorometer is used for measuring fluorescence, which is not applicable for direct titration of chlorine. A pH meter measures the acidity or basicity of a solution and does not provide information about chlorine levels or its titration. Thus, the amperometric titrator stands out as the most suitable choice for this specific application in water quality analysis.