EPA-EAD: 1632: Chemical Speciation of Arsenic in Water and Tissue
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Official Method Name
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Chemical Speciation of Arsenic in Water and Tissue by Hydride Generation Quartz Furnace Atomic Absorption Spectrometry. |
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Current Revision
| Revision A, August 1998 |
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Media
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VARIOUS |
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Instrumentation
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Graphite Furnace-Atomic Absorption Spectrometer |
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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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Brief Method Summary
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After collection, an aliquot of water sample or tissue digestate is placed in a specially designed reaction vessel to which 6M HCl is added, followed by the addition of 4% NaBH4. Arsines are purged from the sample onto a cooled glass trap where they are then thermally desorbed into an inert gas stream that carries them into an atomic absorption spectrophotometer for detection. |
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Scope and Application
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This method determines inorganic arsenic (IA), arsenite (Ar+3), arsenate (As+5), monomethylarsonic acid (MMA), and dimethylarsinic (DMA) in filtered and unfiltered water and in tissue. |
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Applicable Concentration Range
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0.01-50 ug/L in water. 0.10-500 ug/g dry weight of tissue. |
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Interferences
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(A) Glassware contamination: Thoroughly clean glassware prior to use. (B) Reagent contamination: Use high quality reagents. (C) Contamination by carryover: May occur when a sample containing low concentrations of As is processed immediately after a sample containing relatively high concentrations of As. Rinse sample introduction system between samples with a dilute acid and reagent water. (D) Contamination by samples: Samples containing high concentrations should not be permitted into the clean room and laboratory dedicated for processing trace metal samples. (E) Contamination by indirect contact: Every piece of apparatus directly or indirectly used in the collection, processing, and analysis of water and tissue samples should be thoroughly cleaned. (F) Contamination by airborne particulate matter: Sample processing and analysis should occur as far as possible from sources of airborne contamination such as dust, dirt, particles, vapors, corroded or rusted pipes, wires, or metal-containing paint. (G) Water vapor may condense in the transfer line if it is not well heated, interfering with the determination of DMA. |
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Quality Control Requirements
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The minimum requirements include an initial demonstration of laboratory capability, analysis of samples spiked with As and/or As species to evaluate and document data quality, and analysis of standards and blanks as tests of continued performance. |
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Sample Handling
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Samples collected according to Sampling Method (References 16.3 and 16.10 in the method), filtered (if necessary) and preserved. Water samples are acidified to pH < 2 with 3 mL 6M HCl/L sample and stored at 0-4oC. Store the preserved sample for a minimum of 48 hours to allow the As adsorbed on the container walls to completely dissolve in the acidified sample. Tissue samples must be frozen in the sampling container at less than -18oC or freeze-dried and stored at room temperature. |
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Maximum Holding Time
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28 days (aqueous samples). 2 years (tissue samples). |
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Relative Cost
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$201 to $400 |
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Sample Preparation Methods
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None. |
