AOAC: 973.41: pH of Water
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Official Method Name
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pH of Water |
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Current Revision
| 15th Edition (1990) |
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Media
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WATER |
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Instrumentation
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pH Meter |
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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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pH, which is accepted measure of acidity or alkalinity, is determined by change in potential of glass-saturated calomel electrodes, as measured by commercial apparatus standardized against standard buffer solutions whose pH values are assigned by NIST. pH of most natural H2O falls within 4-9. Majority of waters are slightly basic from presence of CO3-HCO3 system. |
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Scope and Application
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Method is applicable to drinking, surface, and saline waters, and domestic and industrial wastes. Oils and greases may cause a sluggish response by coating electrodes. |
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Applicable Concentration Range
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Interferences
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(1) Sodium error may bias results at pH > 10 unless a "low sodium error" electrode is used. (2) Coatings of oily material can impair electrode. (3) Temperature effects. |
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Quality Control Requirements
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Use of three standards to check linearity of electrode response |
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Sample Handling
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Analyze sample as soon as possible. Do not open sample bottle before analysis. |
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Maximum Holding Time
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ASAP |
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Relative Cost
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Less than $50 |
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Sample Preparation Methods
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