EPA-RCA: 9012A: Cyanides, Total and Amenable (CN- Amenable) by Colorimetry
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Official Method Name
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Total and Amenable Cyanide (Automated Colorimetric with off-line Distillation) |
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Current Revision
| Revision 1, December 1996 |
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Media
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VARIOUS |
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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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The cyanide, as hydrocyanic acid (HCN), is released from samples containing cyanide by means of a reflux-distillation operation under acidic conditions and absorbed in a scrubber containing sodium hydroxide solution. The cyanide ion in the absorbing solution is then determined by automated UV colorimetry. In the automated colorimetric measurement, the cyanide is converted to cyanogen chloride (CNCl) by reaction with Chloramine-T at a pH less than 8 without hydrolyzing to the cyanate. After the reaction is complete, color is formed on the addition of pyridine-barbituric acid reagent. The concentration of NaOH must be the same in the standards, the scrubber solutions, and any dilution of the original scrubber solution to obtain colors of comparable intensity. |
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Scope and Application
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Method 9012 is used to determine the concentration of inorganic cyanide (CAS Registry Number 57-12-5) in wastes or leachate. The method detects inorganic cyanides that are present as either soluble salts or complexes. It is used to determine values for both total cyanide and cyanide amenable to chlorination. The "reactive" cyanide content of a waste, that is, the cyanide content that could generate toxic fumes when exposed to mild acidic conditions, is not distilled by Method 9012 (refer to Chapter Seven). However, Method 9012 may be used to quantify the concentration of cyanide from the reactivity test. |
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Applicable Concentration Range
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0.02 - 1mg/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) Glucose/Sugars causes interference during distillation. (7) Sulfur-containing compound causes interference during distillation by forming free sulfide that is captured in distillate. (8) High results may be obtained for samples that contain nitrate and/or nitrite. The possibility of interference of nitrate and nitrite is eliminated by pretreatment with sulfamic acid just before distillation. Nitrate and nitrite are interferences when present at levels higher than 10 mg/L and in conjunction with certain organic compounds. |
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Quality Control Requirements
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Refer to Chapter One for specific quality control procedures. QC procedures include: calibration verification with an independent calibration check standard, matrix spike sample for every 10 samples, and the use of the method of standard additions for the analysis of all samples that suffer from matrix interferences. |
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Sample Handling
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Collect samples in glass or plastic containers. If oxidizing agents are present, add sodium arsenite at time of collection. Preserve aqueous samples at time of collection with 50% sodium hydroxide until pH is equal to or greater than 12. Refrigerate at 4oC and begin preparation within 14 days. Extract solid and oily wastes by Method 9013 prior to analysis. Extract fatty acids, detergents, and surfactants by adding acetic acid to a sample until the pH is 6-7, then extract with isooctane, hexane, or chloroform and immediately adjust the pH to above 12 with NaOH. |
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Maximum Holding Time
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See Chapter Three for information |
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Relative Cost
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Less than $50 |
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Sample Preparation Methods
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