EPA-NERL: 335.4: Cyanide, total, by Colorimetry
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Official Method Name
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Determination of Total Cyanide by Semi-Automated Colorimetry |
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Current Revision
| Revision 1.0, August 1993 |
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Media
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WATER |
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Instrumentation
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Automated Spectrophotometer |
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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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The cyanide as hydrocyanic acid (HCN) is released from cyanide complexes by means of a reflux-distillation operation and is absorbed in a scrubber containing sodium hydroxide solution. The cyanide ion is determined using an automated colorimeter with pyridine-barbituric acid chemistry. |
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Scope and Application
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This method is determines cyanide in drinking, surface and saline waters; and domestic and industrial wastes. |
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Applicable Concentration Range
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0.005 to 0.5 mg/L |
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Interferences
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(1) Oxidizing agents can destroy cyanides during storage. (2) Sulfide can complex with cyanide in sample or distillate. (3) Fatty acids cause interference during distillation. (4) Carbonate causes interference during distillation. (5) Aldehydes cause interference during distillation. (6) Nitrate/Nitrate causes interference during distillation (they can generate cyanides when combined with certain organic compounds). (7) Sulfur-containing compound causes interference during distillation by forming free sulfide that is captured in distillate. |
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Quality Control Requirements
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The minimum requirements consist of an initial demonstration of laboratory capability, the periodic analysis of laboratory reagent blanks, fortified blanks, and other laboratory solutions as a continuing check on performance. |
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Sample Handling
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Test for and remove sulfides using lead acetate paper and cadmium carbonate, respectively. Test sample for the presence of oxidizing agents using KI-starch paper. If oxidizers are detected, add ascorbic acid until a drop test is negative. Preserve samples by adjusting to a pH > 12 with NaOH. Refrigerate samples at 4 degrees C until analysis. Analyze samples as soon as possible. |
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Maximum Holding Time
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14 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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