USGS-NWQL: I-5300-85: Cyanide, Colorimetric, Pyridine-Pyrazolone, Bottom material
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Official Method Name
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Cyanide, Colorimetric, Pyridine-Pyrazolone |
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Current Revision
| 1989 |
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Media
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SOILS/SEDIMENT |
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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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Methods for the Determination of Inorganic Substances in Water and Fluvial Sediments, Techniques of Water-Resources Investigations of the United States Geological Survey, Book 5, Chapter A1 Edited by Marvin J. Fishman and Linda C. Friedman |
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Brief Method Summary
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This method is based on the chlorination of cyanide and the subsequent reaction of the product with a mixed solution of pyridine-pyrazolone to form a stable complex dye. The method detects only simple cyanides; therefore, any complex cyanides present must be broken down. The decomposition of complex cyanides is accomplished by an acid reflux and distillation prior to the colorimetric procedure. The distillation also removes certain interferences from water samples. |
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Scope and Application
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This method may be used to determine cyanide in bottom material containing at least 0.5 mg/kg. |
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Applicable Concentration Range
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0.5 |
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Interferences
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Common interferences include sulfide, heavy-metal ions, fatty acids, steam-distillable organic compounds, cyanate, thiocyanate, glycine, urea, oxidizing agents, and substances that may contribute color or turbidity to the sample. These interferences may be removed or their effect minimized as follows: Sulfide can be removed as lead sulfide by adding a slight excess of lead carbonate to 400 mL of the alkaline (pH 11.0 or above) sample. Filter the sample immediately, wash the precipitate with demineralized water, and add the washings to the filtrate; Fatty acids can be removed by acidifying 400 mL of sample with acetic acid to a pH of between 6 and 7, and by extracting with 80 mL of either isooctane or hexane. A single extraction is usually sufficient; Oxidizing agents can be removed by adding sodium sulfite solution to 400 mL of sample until a negative test with starch-iodide paper is obtained; Most remaining interferences are removed by the distillation. This method includes no provisions for removing these interferences or for minimizing their effects in water-suspended sediment and bottom material. The analyst must be aware that, when such interfering substances are present, the analytical result obtained may be in error, although distillation of the cyanide certainly separates it from some of the interfering substances. |
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Quality Control Requirements
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Quality-control samples area analyzed at a minimum of one in every ten samples. These QC samples include at least one of each of the following: blanks, quality control samples, third party check solutions, replicates, and spikes. Correlation coefficients for calibration curves must be at least 0.99. QC samples must fall within 1.5 standard deviations of the mean value. If all of the data-acceptance criteria in the SOPs are met, then the analytical data are acceptable. |
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Sample Handling
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Description: 500 mL polypropylene bottle, wide-mouth. Chill and maintain at 4oC, +/- 2oC, ship immediately. |
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Maximum Holding Time
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30 days from sampling |
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Relative Cost
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$51 to $200 |
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Sample Preparation Methods
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