USGS-OWQ: NFM 6.2.2-Spec: Dissolved-oxygen concentrations, field measurement by spectrophotometry
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Official Method Name
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Dissolved Oxygen, Spectrophotometric Method |
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Current Revision
| 02/07/2006 |
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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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Dissolved-oxygen measurement in suboxic natural water; must be made in situ to exclude air contact. The spectrophotometric method used by the USGS is based on a Rhodazine-D colorimetric technique developed by CHEMIetrics, Inc. and is used most commonly to measure low concentrations of dissolved oxygen (DO) in ground water and suboxic lake regimes. The reagent reacts with dissolved oxygen to produce an oxidized complex characterized by a red-blue color; color intensity is proportional to the concentration of the initial dissolved oxygen present. |
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Scope and Application
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This method covers the spectrophotometric determination of dissolved-oxygen concentration in suboxic natural waters (commonly for low-DO ground waters and lake waters). |
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Applicable Concentration Range
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0.1 to 1.4 |
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Interferences
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Measurement is affected by presence of reducible inorganic species, e.g., chlorine, ferric and cupric ions, hexabelant chromium; color; and turbidity (ref. TWRI Book 9, Ch.A6.2.2.B). |
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Quality Control Requirements
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Special calibration procedures using atmospheric oxygen standards are needed if measuring dissolved oxygen in acidic or heavily contaminated waters. Bias assessment is required if measurement is in colored or turbid waters. |
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Sample Handling
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Not applicable -- measurement must be made in situ. |
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Maximum Holding Time
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Zero |
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Relative Cost
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Unknown |
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Sample Preparation Methods
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None |
