NEMI Method Summary

Method Summary Information

Method Number: 330.4 Media: WATER
Revision: Issued 1978
Method Source: U.S. EPA National Exposure Research Laboratory (NERL) [formerly EMSL]
Analytes in this method
Subcategory: INORGANIC
Official Name: Chlorine, Total Residual (Titrimetric, DPD-FAS)
Descriptive Name Total Residual Chlorine by Titration
Source Info: U.S.EPA National Exposure Research Laboratory (NERL)
Microbiological and Chemical Exposure Assessment Research Division (MCEARD)
[formerly the Environmental Monitoring Systems Laboratory (EMSL), Cincinnati, OH]
26 West Martin Luther King Drive
Cincinnati, Ohio 45268-0001
Fax: 513-569-7757
email: DWmethods.help@epa.gov
Citation: Methods for the Chemical Analysis of Water and Wastes (MCAWW) (EPA/600/4-79/020)
15991 Byte file
Brief Method
Summary:
 Chlorine (hypochlorite ion, hypochlorous acid) and chloramines stoichiometrically liberate iodine from potassium iodide at pH 4 or less. The iodine is titrated with FAS using DPD as the indicator. The results are calculated as mg/L Cl even though the actual measurement is of total oxidizing power because chlorine is the dominant oxidizing agent present.
Scope And
Application:
 The N,N-diethyl-p-phenylene diamine (DPD) - ferrous ammonium sulfate (FAS) titration method is applicable to natural and treated waters at concentrations above 0.1 mg/L Cl.
Applicable
Conc Range:
 Greater than 0.1 mg/L.
Interferences: Bromine, bromamine, and iodine are interferences which are normally present in insignificant amounts.
Oxidized manganese interferes but can be corrected by subtraction after performing a titration in the presence of sodium arsenite (NaAsO2).
Copper interferes but is accounted for (up to approximately 10 mg/L copper) by incorporation of EDTA. The EDTA also retards deterioration of DPD due to oxidation and completely suppresses dissolved oxygen errors by preventing trace metal catalysis.
Turbidity and color may make the endpoint difficult to detect. Practice runs with spiked samples may be necessary.
QC Requirements: None.
Sample Handling: None.
Max Holding Time:
 Analyze Immediately.
Sample Prep Met None.
Relative Cost: Less than $50
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