EPA: 9016: Free cyanide in water, soils, and solid wastes by microdiffusion
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Official Method Name
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METHOD 9016: FREE CYANIDE IN WATER, SOILS AND SOLID WASTES BY MICRODIFFUSION |
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Current Revision
| Original method, June 2010 |
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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 water, wastewater or extract sample is introduced in the outer chamber of the microdiffusion cell and is buffered at pH 6 and placed in the dark for 6 hrs of diffusion. The free cyanide diffuses as HCN gas and is absorbed as CN- into the sodium hydroxide solution located in the center chamber of the microdiffusion cell. An aliquot of the sodium hydroxide absorber solution is removed and treated with acidified phosphate buffer and chloramine-T to convert the CN- to cyanogen chloride. The cyanogen chloride is reacted with pyridine-barbituric acid to form a color complex that absorbs at 578 to 587 nm. The free cyanide is determined spectrophotometrically by measuring the absorbance of the sample and determining the concentration through comparison with a standard calibration curve. Solids are first extracted prior to analysis using pH 12.3-12.5 NaOH solution. The filtered extracts are then diffused and analyzed spectrophotometrically. |
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Scope and Application
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This test method covers the determination of free cyanide in waste waters, ground waters, surface waters, drinking waters, soils and solid wastes. |
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Applicable Concentration Range
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Based on the calibration curve in the method, the applicable concentration range is approximately 2.0 to 150 ug/L. |
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Interferences
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(A) Chlorine: Removed by adding excess amounts of sodium arsenite or sodium thiosulfate to the sample prior to storage. (B) Sulfides: Removed by adding an excess of either lead carbonate or lead acetate to the sample. (C) Volatility loss if not analyzed immediately: Adjust pH to 12 or greater. (D) Decomposition of hexacyanoferrate complexes producing free cyanide: Maintain darkness during sample diffusion. (E) Artifacts or interferents from solvents, reagents, glassware, other equipment and supplies: Analyze method blanks, distill solvents and reagents in all glass systems. |
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Quality Control Requirements
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method blank (MB), duplicate, matrix spike/matrix spike duplicate (MS/MSD), laboratory control sample (LCS), Initial calibration verification (ICV) standard, Continuing calibration verification (CCV) standard, Lower Limit of Quantitation (LLOQ) check standard. |
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Sample Handling
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Samples should be collected in plastic or glass (preferably plastic) containers that are either amber or covered with aluminum foil so as to filter light at 400 nm and below and prevent photodecomposition of metal cyanide complexes. All sample containers must be prewashed with acids, water, and metal-free detergents, if necessary, depending on the use history of the container. All samples whose origin or composition is not well-known should be tested for the presence or absence of oxidizing agents, sulfides, as specified in the method. Analyze samples immediately; otherwise preserve them at the time of collection, following any treatment for oxidizing agents or sulfides, by adding 50% sodium hydroxide, until the pH is equal to or slightly greater than 12. |
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Maximum Holding Time
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In the dark at 4 ± 2 °C up to 14 days prior to analysis. Extract solids within 14 days of sample collection and analyze within 24 hrs following extraction. |
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Relative Cost
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Sample Preparation Methods
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