Standard Methods: 5540 C: Anionic Surfactants as MBAS

Summary
Analytes
Revisions
Data and Sites

Official Method Name

5540 C. Anionic Surfactants as MBAS

Current Revision

Standard Methods 18th, 19th, 20th ed.

Media

WATER

Instrumentation

Spectroscopy (Colorimetry; Photometry)

Method Subcategory

Organic

Method Source

Standard Methods

Citation

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

Brief Method Summary

Methylene blue active substances (MBAS) bring about the transfer of methylene blue, a cationic dye, from an aqueous solution into an immiscible organic liquid upon equilibration. This occurs through ion pair formation by the MBAS anion and the methylene blue cation. The intensity of the resulting blue color in the organic phase is a measure of MBAS. The method comprises three successive extractions from acid aqueous medium containing excess methylene blue into chloroform (CHCl3), followed by an aqueous backwash and measurement of the blue color in the CHCl3 by spectrophotometry at 652 nm.

Scope and Application

The MBAS method has been applied successfully to drinking water samples. In wastewater, industrial wastes, and sludge, numerous materials normally present can interfere seriously if direct determination of MBAS is attempted. Most nonsurfactant aqueous-phase interferences can be removed by sublation.

Applicable Concentration Range

0.01 - 0.20 mg

Interferences

Positive interferences result from all other MBAS species present; if a direct determination of any individual MBAS species, such as LAS, is sought, all others interfere. Substances such as organic sulfonates, sulfates, carboxylates and phenols, and inorganic thiocyanates, cyanates, nitrates, and chlorides also may transfer more or less methylene blue into the chloroform phase. Negative interferences can result from the presence of cationic surfactants and other cationic materials, such as amines, because they compete with the methylene blue in the formation of ion pairs. Particulate matter may give negative interference through adsorption of MBAS.

Quality Control Requirements

See Section 5020 Quality Assurance/Quality Control.

Sample Handling

Because of inherent properties of surfactants, special analytical precautions are necessary. Avoid foam formation because the surfactant concentration is higher in the foam phase than in the associated bulk aqueous phase and the latter may be significantly depleted. If foam is formed, let it subside by standing, or collapse it by other appropriate means, and remix the liquid phase before sampling. Adsorption of surfactant from aqueous solutions onto the walls of containers, when concentrations below about 1 mg/L are present, may seriously deplete the bulk aqueous phase. Minimize adsorption errors, if necessary, by rinsing container with sample, and for anionic surfactants by adding alkali phosphate (e.g., 0.03N KH2PO4).

Maximum Holding Time

48 hours (Max Storage Recommended) - Regulatory holding time Not Specified

Relative Cost

$51 to $200

Sample Preparation Methods

This method has 1 analyte associated with it.

Analyte	Detection Level	Bias	Precision	Pct False Positive	Pct False Negative	Spiking Level
Surfactants(E-14562) MBAS Methylene Blue Active Substances Surfactants	0.025 mg/L	1Rel. Error (ML)	9.10 % RSD (ML)			2.94 mg/L

Precision Descriptor Notes:	A synthetic sample containing 270 ug LAS/L in distilled water was analyzed in 110 laboratories with a relative standard deviation of 14.8% and a relative error of 10.6%. A tap water sample to which was added 480 ug LAS/L was analyzed in 110 laboratories with a relative standard deviation of 9.9% and a relative error of 1.3%. A river water sample with 2.94 mg LAS/L added was analyzed in 110 laboratories with a relative standard deviation of 9.1% and a relative error of 1.4%.
Detection Level Note:	About 10 ug MBAS (calculated as LAS). The method is applicable at MBAS concentrations down to about 0.025 mg/L.

Precision Descriptor Notes:

A synthetic sample containing 270 ug LAS/L in distilled water was analyzed in 110 laboratories with a relative standard deviation of 14.8% and a relative error of 10.6%. A tap water sample to which was added 480 ug LAS/L was analyzed in 110 laboratories with a relative standard deviation of 9.9% and a relative error of 1.3%. A river water sample with 2.94 mg LAS/L added was analyzed in 110 laboratories with a relative standard deviation of 9.1% and a relative error of 1.4%.

Detection Level Note:

About 10 ug MBAS (calculated as LAS). The method is applicable at MBAS concentrations down to about 0.025 mg/L.

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

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: 5540 C: Anionic Surfactants as MBAS

WHO WE ARE

LEGAL