This method is used for the analysis of free (non-complexed) cyanide and hydrocyanic acid in drinking water, natural surface waters, domestic and industrial wastewaters, and in soil extracts. This method may also be used as a determinative step for quantifying total and amenable cyanide in the alkaline distillates from Method 9010.
There are two options for analysis: colorimetric and titrimetric.
The titration procedure using silver nitrate with a p-dimethylamino-benzal-rhodanine indicator to measuring concentrations of cyanide exceeding 0.1 mg/L.
The colorimetric procedure converts cyanide to cyanogen chloride (CNCl) by reaction of cyanide with chloramine-T at a pH less than 8. After the reaction is complete, color is formed on the addition of pyridine-barbituric acid reagent. The absorbance is read at 578 nm for the complex formed with pyridine-barbituric acid reagent and CNCl. To obtain colors of comparable intensity, it is essential to have the same salt content in both the sample and the standards. The colorimetric procedure is used for concentrations below 1 mg/L of cyanide and is sensitive to about 0.02 mg/L.
Chlorine and sulfide are potential interferences with this method.
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| Hold Times, Preservatives, Preps, Collection, Analytical & Documentation | |
|---|---|
| Holding Time: | No longer than 14 days. |
| Preservatives: | Adjust pH to greater than 12 with sodium hydroxide. Protect from light. |
| Required Preps: | Poly bottle |
| Collection Method: | Grab Sampling. |
| Analytical Methodology: | Spectrophotometric or Titrimetric. |
| Documentation: | 
9014
|
| Analyte | Formula | CAS Number | Detection Limit | |
|---|---|---|---|---|
| Cyanides | CN- |
57-12-5 |
1 |
mg/L |
| Hydrogen cyanide | HCN |
74-90-8 |
1 |
mg/L |
| Cyanide, Free | 0.02 |
mg/L | ||
* The analytes and detection limits listed for each method represent the typical detection limits and analytes reported for that particular method. Keep in mind that analyte lists may vary from laboratory to laboratory. Detection limits may also vary from lab to lab and are dependent upon the sample size, matrix, and any interferences that may be present in the sample.