Hach Co.: 28000-88: Arsenic Test Strip
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Official Method Name
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Arsenic |
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Current Revision
| Jul-00 |
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Media
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WATER |
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Instrumentation
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Color Strip Indicator |
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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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Hydrogen sulfide is first oxidized to sulfate to prevent interference, and the oxidizing environment is then neutralized. Sulfamic acid and powdered zinc react to create strong reducing conditions in which inorganic arsenic is reduced to arsine gas (AsH3). The arsine gas then reacts with mercuric bromide in the test strip to form mixed arsenic/ mercury halogenides that discolor the test strip. The color ranges from yellow through tan to brown, depending on the concentration. If organic + inorganic arsenic is desired: Collect 50 mL of sample in a glass beaker. Add the first two reagents according to the instructions. Place the beaker in a boiling water bath for 30 minutes. Remove the beaker from the water bath and transfer the contents to the reaction vessel. Allow the sample to cool to room temperature, then complete the procedure, beginning with step 6. |
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Scope and Application
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Applicable to natural waters, drinking water and groundwater. The instructions, as written for this test, are designed to detect inorganic arsenic. However, orgainc + inorganic arsenic can be determined with appropriate method modification, as described in the Method Summary. |
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Applicable Concentration Range
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10-500 ug/L |
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Interferences
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The following were found to interfere: (1) Sulfide > 5 mg/L; (2) Selenium > 1 mg/L; (3) Antimony > 250 ug/ L; (4) Tellurium likely to interfere, but not tested. The following did not interfere at the levels tested: (1) Hardness 1000 mg/L as CaCO3; (2) Alkalinity 1000 mg/L as CaCO3; (3) Iron 10 mg/L; (4) Temperature 10 to 40oC. |
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Quality Control Requirements
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Not provided in the method. The Hach Water Handbook contains a general discussion of QC practices. |
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Sample Handling
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It is recommended that samples be tested immediately after collection. If samples must be preserved, do not use Nitric Acid as it interferes in the test. Adjust pH to 2 with H2SO4. Samples can be held for up to 6 months. Before performing the analysis adjust pH to between 6-7 with NaOH. |
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Maximum Holding Time
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6 months. |
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Relative Cost
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Less than $50 |
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Sample Preparation Methods
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