Standard Methods: 4500-O C: Oxygen by Azide Modification

Summary
Analytes
Revisions
Data and Sites

Official Method Name

4500-O C. Azide Modification

Current Revision

Standard Methods Online

Media

WATER

Instrumentation

Titration with Color Indicator

Method Subcategory

Inorganic

Method Source

Standard Methods

Citation

Standard Methods Online - Standard Methods for the Examination of Water and Wastewater

Brief Method Summary

Manganous sulfate is added to the sample. Then a strongly basic mixture of sodium azide and potassium iodide is added. A precipitate forms and is then acidified with sulfuric acid. Iodine is released and titrated with phenylarsine oxide using a starch indicator.

Scope and Application

Use the azide modification for most wastewater, effluent, and stream samples, especially if samples contain more than 50 ug Nitrite-N/L and not more than 1 mg Ferrous iron/L.

Applicable Concentration Range

Interferences

Nitrite and ferrous ion interfere. Other reducing or oxidizing materials should be absent.

Quality Control Requirements

See Section 4020 Quality Assurance/Quality Control.

Sample Handling

Collect samples very carefully. Methods of sampling are highly dependent on source to be sampled and, to a certain extent, on method of analysis. Do not let sample remain in contact with air or be agitated, because either condition causes a change in its gaseous content. Samples from any depth in streams, lakes, or reservoirs, and samples of boiler water, need special precautions to eliminate changes in pressure and temperature. Collect surface water samples in narrow-mouth glass-stoppered BOD bottles of 300-mL capacity with tapered and pointed ground-glass stoppers and flared mouths. Avoid entraining or dissolving atmospheric oxygen. In sampling from a line under pressure, attach a glass or rubber tube to the tap and extend to bottom of bottle. Let bottle overflow two or three times its ~ volume and replace stopper so that no air bubbles are entrained.

Maximum Holding Time

0.25 hour (See Section 1060)

Relative Cost

Less than $50

Sample Preparation Methods

This method has 1 analyte associated with it.

Analyte	Detection Level	Bias	Precision	Pct False Positive	Pct False Negative	Spiking Level
Dissolved Oxygen(E-14539) DO Dissolved Oxygen	N/A	N/A	N/A

Precision Descriptor Notes:	Dissolved oxygen (DO) can be determined with a precision, expressed as a standard deviation, of about 20 ug/L in distilled water and about 60 ug/L in wastewater and secondary effluents. In the presence of appreciable interference, even with proper modifications, the standard deviation may be as high as 100 ug/L. Still greater errors may occur in testing waters having organic suspended solids or heavy pollution. Avoid errors due to carelessness in collecting samples, prolonging the completion of test, or selecting an unsuitable modification.
Detection Level Note:

Precision Descriptor Notes:

Dissolved oxygen (DO) can be determined with a precision, expressed as a standard deviation, of about 20 ug/L in distilled water and about 60 ug/L in wastewater and secondary effluents. In the presence of appreciable interference, even with proper modifications, the standard deviation may be as high as 100 ug/L. Still greater errors may occur in testing waters having organic suspended solids or heavy pollution. Avoid errors due to carelessness in collecting samples, prolonging the completion of test, or selecting an unsuitable modification.

Detection Level Note:

Revision	PDF/Link
Standard Methods Online
Standard Methods 18th Edition (1992)
Standard Methods 19th Edition (1995)
Standard Methods 18th, 19th, 20th ed.

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Standard Methods: 4500-O C: Oxygen by Azide Modification

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