5.1 The widespread use and discharge of detergents into surface waters can result in a lowering of its aesthetic quality by foam formation and by causing toxicity to aquatic wildlife. This test method is capable of detecting small concentrations of detergents as MBAS so that they can be controlled to prevent such problems.

5.2 Biodegradable linear alkyl benzene sulfonates (LAS) have replaced the branched-chain alkyl benzene sulfonates (ABS) in detergent formulations, which were more resistant to biodegradation. Differentiation between linear and branched-chain alkyl benzene sulfonates, as well as differentiation of the various positional isomers of either type, is not possible by this test method. While the methylene blue method may be employed to monitor studies designed to measure biodegradability, it cannot be used to predict this quality.

1.1 This test method covers the determination of compounds that react with methylene blue under the conditions specified in the test procedure. They are referred to as methylene blue active substances (MBAS), and are calculated and reported in terms of the reference material, linear alkyl benzene sulfonate, LAS.

1.2 This test method is applicable for determining MBAS in water and wastewater. It is the user's responsibility to ensure the validity of this test method for waters of untested matrices.

1.3 This test method is a simple, rapid, control procedure suitable for monitoring the effectiveness of a biodegradation or other linear alkyl benzene sulfonate (LAS) removal process. For greater specificity and interference removal, the pretreatment procedure in Annex A1 should be used. Data derived without the pretreatment procedure should be interpreted with care. This test method is applicable in the range from 0.03 to 1.5 mg/L for a 100-mL sample.

1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. For a specific hazard statement, see 8.3.

1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.