EPA Method 302

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EPA Method 302:
DETERMINATION OF BROMATE IN DRINKING WATERS USING TWO-DIMENSIONAL ION CHROMATOGRAPHY WITH SUPPRESSED CONDUCTIVITY DETECTION

Summary:
Water samples are collected in the field using normal collection techniques and dechlorinated with ethylenediamine (EDA). A 1.0-mL sample aliquot is injected onto a 4-mm IC column. Separation of bromate is achieved in the first dimension (1-D) using 10 mM KOH at a flow rate of 1.0 mL per minute. Approximately 2 mL of the suppressed eluent containing the bromate is diverted from the first dimension column to a concentrator column used in place of the sample loop of the second dimension (2-D) injection valve. The concentrator column has low backpressure but sufficient capacity to trap the bromate ions quantitatively in the suppressed eluent. In this manner, bromate is separated from other matrix ions and concentrated on a trapping column. The heart-cut portion of the 1-D chromatogram is eluted off the concentrator column and onto a smaller diameter (2 mm diameter) guard and analytical column that have different selectivity from the first dimension columns to facilitate the 2-D separation using 10 mM KOH at a flow rate of 0.25 mL per minute. Bromate is quantitated using the external standard method.

Scope:
This is a large volume (1.0 mL), two-dimensional (2-D) ion chromatographic (IC) method using suppressed conductivity detection for the determination of bromate in raw and finished drinking waters. Because this method utilizes two dissimilar IC columns it does not require second column confirmation. Detection and quantitation in the second dimension are accomplished by suppressed conductivity detection. Precision and accuracy data have been generated for bromate using this 2-D IC method in reagent water, finished groundwater, finished 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.

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