USGS-NWQL: I-2192-02: Laboratory arsenic speciation, malonate/acetate mobile phase, ICP-MS detection, dissolved
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Official Method Name
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Laboratory arsenic speciation, malonate/acetate 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 uses a 50-mm column with strong anion exchange packing to rapidly separate arsenite (As(III)) and arsenate (As(V)). A malonate/acetate mobile phase is used to separate the species in about three minutes using high performance liquid chromatography. However, dimethylarsinate (DMA) and monomethylarsonate (MMA), if present, are unresolved and are eluted concurrently with As(III) and As(V). |
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Scope and Application
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This method is used to determine arsenite (As(III)), and arsenate (As(V)) in water. |
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Applicable Concentration Range
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MDL to 100 |
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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 managanese 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. If dimethylarsinate (DMA) or monomethylarsonate (MMA) is present in a sample, they will be eluted concurrently with As(III) and As(V) because of the short column length. 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 inteference. |
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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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Sample Preparation Methods
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