MBAS assay
A methylene blue active substances assay, or MBAS assay, is a
anionic surfactants (such as a detergent or foaming agent) in a sample of water. An anionic surfactant detected by the color reaction is called a methylene blue active substance (MBAS).[1]
After first acidifying a water sample (with
color saturation
of the chloroform increases with the concentration of anionic surfactants.
MBAS assay is an ASTM International standard technique for detecting anionic surfactants.[3] These include carboxylates, phosphates, sulfates, and sulfonates. An MBAS assay alone does not, however, identify specific surfactants. ASTM withdrew the standard (ASTM D2330-02) in 2011 pending a review and update of the method, which was last approved in 2003.[3]
The publication Standard Methods for the Examination of Water and Wastewater lists the following methods used by certified laboratories testing wastewater in the United States.
- Method 5540B describes surfactant separation by sublation.
- Method 5540C discusses anionic surfactants as methylene blue active substances (MBAS).
- Method 5540D discusses nonionic surfactants as cobalt thiocyanate active substances (CTAS).[4]
See also
- Colorimetry
- Surfactant
- Water chemistry analysis
- Water testing
Notes
- ^ Alison L. George, Graham F. White "Optimization of the methylene blue assay for anionic surfactants added to estuarine and marine water" Environmental Toxicology and Chemistry 1999, Volume 18, pages 2232–2236.
- ^ a b "Regulation (EC) No 648/2004 of the European Parliament and of the Council of 31 March 2004 on detergents". EUR-Lex. Luxembourg: European Union. Document 32004R0648.
- ^ a b ASTM International, West Conshohocken, PA. ASTM D2330 - 02 Standard Test Method for Methylene Blue Active Substances
- ISBN 978-0-87553-047-5. Also available on CD-ROM and onlineby subscription.
References
- Nollet, Leo M. L. Handbook of Water Analysis. 2nd ed. New York: Marcel Dekker, 2007.