USGS-NWQL: I-2193-02: Laboratory arsenic speciation, nitric acid mobile phase, ICP-MS detection, dissolved
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Official Method Name
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Laboratory arsenic speciation, nitric acid mobile phase, ICP-MS detection, dissolved |
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Current Revision
| 2002 |
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Media
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WATER |
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Instrumentation
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Inductively Coupled Plasma - Mass Spectrometry |
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Method Subcategory
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Inorganic |
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Method Source
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Citation
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Garbarino, J.R., Bednar, A.J., and Burkhart, M.R., Methods of Analysis of the U.S. Geological Survey National Water Quality Laboratory -- Arsenic Speciation in Natural-Water Samples Using Laboratory and Field Methods, U.S. Geological Survey Water-Resources Investigations Report 02-4144, 47 p. |
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Brief Method Summary
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This method includes modifications of a method described by Jackson and others (2000) for the separation and determination of arsenite (As(III)), arsenate (As(V)), monomethylarsonate (MMA), and dimethylarsinate (DMA) using high performance liquid chromatography with ICP-MS detection. Nitric acid is used as the mobile phase to chromatographically separate arsenic species making it possible to analyze acid mine drainage. |
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Scope and Application
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This method is used to determine dissolved arsenite (As(III)), arsenate (As(V)), monomethylarsonate (MMA), and dimethylarsinate (DMA) in water including acid mine drainage. Addition of 2% (by volume) of methanol to the mobile phase also allows for the separation and determination of roxarsone. |
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Applicable Concentration Range
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MDL to 100 ug/L |
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Interferences
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Chemical and spectral interferences can affect the accuracy of determining arsenic species unless appropriate procedures are followed. Iron and manganese oxyhydroxide precipitates provide sorption sites for dissolved arsenic species that might negatively biasing arsenic speciation results. This effect can be minimized by decreasing the pH to stabilize the cations or by complexation of the cations. Use of an EDTA preservative works best for a wide range of sample matrices. As(III) can be oxidized to As(V) by photolytically prodcued free radicals. Opaque polyethylene sample bottles are used to elminate this effect. Spectral interference from argon-chloride molecular ion at m/z 75 when using ICP-MS to determine arsenic has been documented and suitable correction methods have been established. However, chromatographic separation minimizes chloride interference. |
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Quality Control Requirements
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Calibrate instrument using calibration standards (CAL); quality control samples (QCS); and laboratory blanks (LB) analyzed at a minimum of 1 for every 10 samples. |
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Sample Handling
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Container Description: opaque polyethlyene bottle. Handling and Treatment: Filter at 0.45 um and preserve with EDTA. |
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Maximum Holding Time
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90 days |
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Relative Cost
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Less than $50 |
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Sample Preparation Methods
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