This is a sample pre-concentration, matrix elimination ion chromatographic (IC) method using suppressed conductivity detection for the determination of perchlorate in raw and finished drinking waters. This method requires the use of a confirmation column to validate all perchlorate concentrations reported at or above the MRL on the primary column. Precision and accuracy data have been generated for perchlorate, with both the primary and confirmation columns, in reagent water, finished groundwater, surface water and a Laboratory Fortified Synthetic Sample Matrix (LFSSM). The single laboratory Lowest Concentration Minimum Reporting Level (LCMRL) has also been determined in reagent water.