Boiler feed water is a working medium in thermal power plant. To keep corrosion low, the pH value should be in the slightly alkali range, which is why amines are added to the feed water. This addition must be monitored regularly. Also important is the monitoring of the sodium concentration, because an increase of this indicates that cooling water is seeping into the condenser. Ion chromatography with conductivity detection following sequential suppression is the optimum system for monitoring, particularly in combination with intelligent Sample Preconcentration and Matrix Elimination.