NEMI Method Summary


Method Summary Information

Method Number:

330.5

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 (Spectrophotometric, DPD)

Descriptive Name

Total Residual Chlorine by Spectrophotometer

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)

14437

Byte file

Brief Method
Summary:

Chlorine (hypochlorite ion, hypochlorous acid) and chloramines stoichiometrically liberate iodine from potassium iodide at pH 4 or less. The liberated iodine reacts with N,N-diethyl-p-phenylene diamine (DPD) to produce a red colored solution. The solution is spectrophotometrically compared to a series of standards, using a graph or a regression analysis calculation.

Scope And
Application:

The DPD-Colorimetric method is applicable to natural and treated waters at concentrations from 0.2-4 mg/L.

Applicable
Conc Range:

0.2-4 mg/L.

Interferences:

Any oxidizing agents; these are usually present at insignificant concentrations compared to the residual chlorine concentrations. Turbidity and color will essentially prevent the colorimetric analysis.

QC Requirements:

None.

Sample Handling:

None.

Max Holding Time:

Analyze Immediately.

Sample Prep Met

None.

Relative Cost:

Less than $50

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Method Summary Information