This method is for the determination of methylene blue active substances (MBAS) in drinking waters, surface waters, domestic and industrial wastes. The method not applicable to measurement of surfactant type materials in saline waters. The method is applicable over the range of 0.025 to 100 mg/L LAS.
Methylene blue is added to an aliquot of sample. Methylene blue reacts with anionic-type surface active materials in water matrices to form a blue colored salt which is extracted with chloroform. The intensity of the color produced is measured by UV/VIS spectroscopy. The intensity of the color is proportional to the concentration of MBAS.
The method does not differentiate between linear alkyl sulfonate (LAS) and alkyl benzene sulfonate (ABS) or other isomers of these types of compounds. However, LAS has essentially replaced ABS on the surfactant market so that measurable surfactant materials will probably be LAS type materials.
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| Hold Times, Preservatives, Preps, Collection, Analytical & Documentation | |
|---|---|
| Holding Time: | 48 hours from sample collection to analysis |
| Preservatives: | Recommended to cool sample to 4 °C but not specified in the method. |
| Required Preps: | 250 mL polyethylene bottle |
| Collection Method: | Grab sampling |
| Analytical Methodology: | UV/VIS spectroscopy |
| Documentation: | 
425.1
|
| Analyte | Formula | CAS Number | Detection Limit | |
|---|---|---|---|---|
| Methylene Blue Active Substances (MBAS) | 0.25 |
mg/L | ||
* The analytes and detection limits listed for each method represent the typical detection limits and analytes reported for that particular method. Keep in mind that analyte lists may vary from laboratory to laboratory. Detection limits may also vary from lab to lab and are dependent upon the sample size, matrix, and any interferences that may be present in the sample.