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7.1.12 Ion Chromatography

Use: Analysis of metal cations and anions in water samples.


Ion chromatography is a form of liquid chromatography that uses ion-exchange resins to separate atomic or molecular ions based on their interaction with the resin. Its greatest utility is for analysis of anions for which there are no other rapid analytical methods. Most ion-exchange separations are done with pumps and nonmetallic columns. The column packing for ion chromatography consists of ion-exchange resins bonded to inert polymeric particles (typically 10 mm diameter). For cation separation, the cation-exchange resin is usually a sulfonic or carboxylic acid. For anion separation the anion-exchange resin is usually a quaternary ammonium group. Most ion chromatography instruments use two mobile phase reservoirs containing buffers of different pH, and a programmable pump that can change the pH of the mobile phase during the separation.

Ions in solution can be detected by measuring the conductivity of the solution. In ion chromatography, the mobile phase contains ions that create background conductivity, making it difficult to measure the conductivity due only to the analyte ions as they exit the column. This problem can be greatly reduced by selectively removing the mobile phase ions after the analytical column and before the detector. Converting the mobile phase ions to a neutral form or removing them with an eluent suppressor, which consists of an ion-exchange column or membrane, does this.


7. Metals


Soil/Sediment Water Gas/Air
Requires extraction to liquid or gas phase BETTER Not Applicable
Selectivity: Technique measures the contaminant indirectly.
Susceptibility to Interference: Medium.
Detection Limits : 100-1000 ppb (soil); 1-50 ppb (water).
Turnaround Time per Sample: Minutes, if analysis solutions are prepared prior to field deployment.
Applicable To:
Screen/Identify Characterize Concentration/Extent Cleanup Performance Long-Term Monitoring
Quantitative Data Capability: Produces quantitative data.
Technology Status: Commercially available technology with limited field experience.
Certification/Verification: Technology has not participated in CalEPA certification and/or CSCT verification program.
Relative Cost per Analysis: Mid-range expense.


EPA Methods:

7199 Determination of Hexavalent Chromium in Drinking Water, Groundwater, and Industrial Wastewater Effluents by Ion Chromatography.
9056 Determination of Inorganic Anions by Ion Chromatography.

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