Iron is an essential element in the human diet and is found in many natural and treated waters. Therefore, the World Health Organization (WHO) does not issue a health-based guideline value for iron. Higher concentrations of iron in surface waters can indicate the presence of industrial effluents or outflow from other operations and sources of pollution. Because of this, precise, rapid, and accurate iron determination at low concentrations in environmental and industrial samples is of great importance. This can be achieved with the method described in this Application Bulletin.