Standard Methods: 4110B:  Anions in Water by Ion Chromatography

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Official Method Name
4110 B. Ion Chromatography with Chemical Suppression of Eluent Conductivity
Current Revision
Standard Methods Online
Ion Chromatography
Method Subcategory
Method Source
  Standard Methods
  Standard Methods Online - Standard Methods for the Examination of Water and Wastewater
Brief Method Summary
A water sample is injected into a stream of eluent and passed through a series of ion exchangers. The anions of interest are separated on the basis of their relative affinities for a low-capacity, strongly basic anion exchanger (guard and analytical columns). The separated anions are directed through a suppressor device that provides continuous suppression of eluent conductivity and enhances analyte response. In the suppressor the separated anions are converted to their highly conductive acid forms while the conductivity of the eluent is greatly decreased. The separated anions in their acid forms are measured by conductivity. They are identified on the basis of retention time as compared to standards. Quantitation is by measurement of peak area or peak height.
Scope and Application
This method is applicable, after filtration to remove particles larger than 0.45 um, to surface, ground, and wastewaters as well as drinking water. Some industrial process waters, such as boiler water and cooling water, also may be analyzed by this method.
Applicable Concentration Range
Any substance that has a retention time coinciding with that of any anion to be determined and produces a detector response will interfere. Low-molecular-weight organic acids, bromate, and chlorite may interfere with the determination of chloride and fluoride. A high concentration of any one ion also interferes with the resolution, and sometimes retention, of others. Sample dilution or gradient elution overcome many interferences. Modifications such as preconcentration of samples, gradient elution, or reinjection of portions of the eluted sample may alleviate some interferences but require individual validation for precision and bias and are beyond the scope of this method.
Quality Control Requirements
See Section 4020 Quality Assurance/Quality Control for minimum QC guidelines. Preferably check recovery daily at reporting level using a reporting-level standard. Recovery should be between 75 and 125%. Alternate analysis of mid-range and high-range check standards after each 10 samples. Recovery should be between 90 and 110%. If the results are to be used for environmental compliance monitoring, document precision and accuracy of the method by the analysis of four replicates of a mid-range calibration standard and calculation of the average percent recovery, and the standard deviation of the recoveries, for each analyte. Additional QC may be required for regulatory purposes.
Sample Handling
See Section 1060 Collection and Preservation of Samples under the individual analytes determined.
Maximum Holding Time
See Section 1060 Collection and Preservation of Samples
Relative Cost
$51 to $200
Sample Preparation Methods