USGS-NWQL: O-3128-95: Methylene Blue Active Substances in Water by Spectrophotometry, Whole Water Recoverable
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Official Method Name
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Determination of Methylene Blue Active Substances by Spectrophotometry |
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Current Revision
| 1995 |
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Media
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WATER |
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Instrumentation
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Spectroscopy (Colorimetry; Photometry) |
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Method Subcategory
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Organic |
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Method Source
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Citation
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Burkhardt, M.R., Cinotto, P.J., Frahm, G.W., Woodworth, M.T., and Pritt, J.W., 1995, Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory--Determination of methylene blue active substances by spectrophotometry: U.S. Geological Survey Open-File Report 95-189. |
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Brief Method Summary
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Sulfate and sulfonate-based anionic surfactants are reacted with methylene blue to form a blue-colored complex. The complex is extracted into chloroform, back-washed with an acidified phosphate-based buffer solution, and measured against external standards with a probe spectrophotometer. This method is similar in substance to the MBAS method published by the American Public Health Association (1992). |
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Scope and Application
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This method is used to determine MBAS in drinking-, surface-, and ground-water samples. Samples containing concentrations of MBAS greater than 0.50 mg/L need to be diluted prior to analysis. |
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Applicable Concentration Range
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0.02-0.50 |
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Interferences
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This method was implemented following a customer-requested audit of the MBAS method reported by Wershaw and others (1987, p.57). The NWQL used the customer-provided data, experimental data, and information from the American Public Health Association (1992, p.5-36 to 5-38) to conclude that nitrate and chloride interfere with the MBAS determination described by Wershaw and others (1987, p.57). Other compounds interfere with the determination of MBAS (American Public Health Association, 1992) but are assumed to interfere to a lesser degree on the basis of their reactivity and low environmental concentration (American Public Health Association, 1992). |
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Quality Control Requirements
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Quality-control samples area analyzed at a minimum of one in every ten samples. These QC samples include at least one of each of the following: blanks, quality control samples, third party check solutions, replicates, and spikes. Correlation coefficients for calibration curves must be at least 0.99. QC samples must fall within 1.5 standard deviations of the mean value. If all of the data-acceptance criteria in the SOPs are met, then the analytical data are acceptable. |
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Sample Handling
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Maximum Holding Time
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Relative Cost
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Sample Preparation Methods
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