Standard Methods: 3500-Cr B: Chromium by Colorimetry

Summary
Analytes
Revisions
Data and Sites

Official Method Name

3500-Cr B. Colorimetric Method

Current Revision

Standard Methods Online

Media

WATER

Instrumentation

Spectroscopy (Colorimetry; Photometry)

Method Subcategory

Inorganic

Method Source

Standard Methods

Citation

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

Brief Method Summary

This procedure measures only hexavalent chromium, (Cr6+). For total chromium determination, acid-digest the sample and follow with a suitable instrumental analysis technique. The hexavalent chromium is determined colorimetrically by reaction with diphenylcarbazide in acid solution. A red-violet colored complex of unknown composition is produced. The reaction is very sensitive.

Scope and Application

The colorimetric method is useful for the determination of hexavalent chromium in a natural or treated water in the range from 100 to 1000 ug/L. This range can be extended by appropriate sample dilution or concentration and/or use of longer cell paths.

Applicable Concentration Range

100 to 1000 ug Cr/L

Interferences

The reaction with diphenylcarbazide is nearly specific for chromium. Hexavalent molybdenum and mercury salts will react to form color with the reagent but the intensities are much lower than that for chromium at the specified pH. Other intereferences are molybdenum, mercury, vanadium, and iron.

Quality Control Requirements

See Section 3020 Quality Assurance/Quality Control.

Sample Handling

Plastic or glass containers. Refrigerate. If only the dissolved chromium content is desired, filter sample immediately through a 0.45-um membrane filter at time of collection, and acidify filtrate with HNO3 to pH <2. If only dissolved hexavalent chromium is desired, adjust pH of filtrate to 9 with 1N sodium hydroxide solution and refrigerate to 4 +/-2 degrees C. If the total chromium content is desired, acidify unfiltered sample at time of collection with conc HNO3 to pH <2. If total hexavalent chromium is desired, adjust the pH of unfiltered sample to 9 with 1N sodium hydroxide and refrigerate to 4 +/-2 degrees C.

Maximum Holding Time

24 hours (See Section 1060)

Relative Cost

Less than $50

Sample Preparation Methods

This method has 2 analytes associated with it.

Analyte	Detection Level	Bias	Precision	Pct False Positive	Pct False Negative	Spiking Level
Chromium(7440-47-3) Chromium Cr	100.000 ug/L	N/A	N/A
Hexavalent chromium(18540-29-9) Chrome(VI) Chromium (+6) Chromium (VI) Chromium hexavalent ion Chromium(VI) Chromium, hexavalent Hexavalent chrome Hexavalent chromium	N/A	N/A	N/A

Precision Descriptor Notes:	Collaborative test data from 16 laboratories were obtained on reagent water, tap water, 10% NaCl solution, treated water from synthetic organic industrial waste, EPA extraction leachate, process water, lake water, and effluent from a steel pickle liquor treatment plant. The precision relationships are given as equations in the method.
Detection Level Note:	Lowest level of stated method range.

Revision	PDF/Link
Standard Methods Online
As Method 3500-Cr D in Standard Methods 18th Edition (1992)
As Method 3500-Cr D in Standard Methods 19th Edition (1995)
Standard Methods 18th, 19th, 20th ed.

The Water Quality Portal contains sample results from sites that use this method.

Download WQP data

Select data:

Sites only
Sample results only

File format:

Comma-separated
Tab-separated
MS Excel 2007+

Sites where this method was used

Loading Sites ...

Standard Methods: 3500-Cr B: Chromium by Colorimetry

WHO WE ARE

LEGAL