This document specifies a method for the determination of dissolved perchlorate in water (e.g. drinking water, mineral water, raw water, surface water, partially treated water or swimming pool water, waste water from drinking/swimming pool water treatment plants). Appropriate pre-treatment of the sample (e.g. matrix elimination) allows a direct determination of perchlorate e" 1 ¼g/l. The working range is restricted by the ion exchange capacity of the separator column. Dilution of the sample to the working range can be necessary.