ASTM: D1252B: COD, Micro, by Sealed Digestion and Spectrometry (Test Method B)
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Official Method Name
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Standard Test Methods for Chemical Oxygen Demand (Dichromate Oxygen Demand) of Water |
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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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Inorganic |
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Method Source
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Citation
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Brief Method Summary
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A sample aliquot and reagents are sealed in an ampule or tube and heated in an oven, sand bath, or heated block at 150 degrees C for 2 h. The COD concentration is determined spectrophotometrically after digestion. In the low COD range (5 to approximately 50 mg/L), the loss of hexavalent chromium is measured at 420 nm, while for the high range (50 to approximately 800 mg/L), the increase in trivalent chromium is measured at 600 nm. The ampule or tube serves as the absorption cell. |
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Scope and Application
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This test method is essentially equivalent to Test Method A, but it utilizes micro volumes of the same reagents contained in a sealable ampule or a screw-top culture tube and a spectrophotometer or filter photometer to measure absorbance or transmittance at selected wavelengths. This test method is applicable where only small sample volumes are available and where large numbers of samples need to be analyzed. This test method requires less space per analysis and uses less of the reagents, minimizing costs and volume of wastes discharged. |
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Applicable Concentration Range
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5 - 800 mg/L |
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Interferences
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Interferences identified in Method A are also applicable to the micro procedure. Spectrophotometric interferences may exist due to turbidity of precipitated salts that are too colloidal to settle in a reasonable period of time. |
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Quality Control Requirements
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Sample Handling
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Collect the sample in accordance with Practices D 3370. Preserve samples by cooling to 4 |
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Maximum Holding Time
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28 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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