| Introduction | | | | ion. Once the cyanide ion is trapped in the absorber |
| Each time you distill samples for cyanide analysis, you | | | | solution it can be analyzed by any one of the |
| are wasting your time and money. OIA 1677 and OIA | | | | determinative steps to quantitate cyanide in solution. |
| 1678 provide more precise and accurate cyanide | | | | Note that the procedure described is not really a |
| analysis data using automated gas-diffusion | | | | distillation. Instead, it is boiling the sample in sulfuric |
| amperometry, while decreasing cyanide interferences. | | | | acid, condensing the steam back into the sample, and |
| OIA1677 is EPA approved for available cyanide in | | | | collecting all gases created (including the HCN) in a |
| wastewater, and for free cyanide in drinking water. A | | | | dilute sodium hydroxide solution. The cyanide |
| new methods, ASTM D7511-09 (or OIA1678) is | | | | recovered by this process, in interference free |
| currently proposed for nationwide use for Clean | | | | samples, has been defined as "total cyanide." |
| Water Act compliance. This method will appear in a | | | | The predominant determination step is pyridine |
| Federal Register notice sometime later this year. | | | | barbituric acid colorimetry. While some methods (EPA |
| Cyanide is a widely used chemical that is found in | | | | 335.4) use automation for the measurement, the |
| many other industries than the mining that it is most | | | | sample preparation still requires manual processing, |
| commonly associated with. These industries need to | | | | which requires manual labor. It is this manual |
| analyze cyanide in their process streams and | | | | processing that limits the number of samples your lab |
| wastewater, and their matrices will have other | | | | can analyze per day. It is the manual processing that |
| constituents that interfere with cyanide distillations. | | | | increases the cost of each sample. You may spend |
| We could continue with status quo and analyze as its | | | | tens of thousands of dollars on an auto analyzer, but |
| always been done, or we could begin to be more | | | | if you are still distilling manually, you are not realizing |
| concerned about the data generated, and less | | | | the full benefits of that automation. |
| concerned about continued use of methodology that | | | | Most EPA approved cyanide methods utilize |
| has been proven to not work. | | | | automated equipment following a manual distillation |
| Analysis of Cyanide in Drinking Water | | | | step. This preliminary distillation is not only causing |
| Did you know that OIA1677 has been approved for | | | | your reported results to be questionable, but is also |
| SDWA compliance reporting since March 2007? Don't | | | | costing you money. You can, by demonstrating that |
| feel bad, not many people do. One of the reasons is | | | | your samples contain interferences, use an alternative |
| a common misconception that drinking water is | | | | procedure, such as ASTM D7511, to overcome those |
| regulated for total cyanide. The regulated parameter | | | | interferences. This non-distillation alternative will raise |
| for SDWA compliance is free cyanide as defined by | | | | your confidence in your results and greatly improve |
| the CATC method, or by OIA 1677-DW. Another | | | | throughput while lowering cost. |
| reason is, essentially, tradition. Before OIA1677 | | | | EPA has proposed ASTM D7511 for inclusion in the |
| existed there were no methods capable of running | | | | next method update rule. ASTM D7511 is the same |
| free cyanide directly. | | | | method as OIA1678. This, formerly proprietary |
| Instead the CATC method was used. CATC is a | | | | method, was handed to the ASTM allowing members |
| two-step, and very time consuming method. The | | | | of the ASTM D19.06 committee to revalidate the |
| general consensus came that if you "screen" a | | | | method and generate data in their own matrices |
| sample for total cyanide and it is not detected there | | | | confirming its claims. The method was validated by |
| is no reason to run CATC. If, and only if, total | | | | an inter-laboratory study on 9 very complex matrices |
| cyanide is detected would you continue with the | | | | taken from the industrial effluents known to contain |
| CATC and report that result. OIA 1677 eliminates the | | | | cyanide and its interferences. It is my opinion that |
| requirement for distillation and analyzes SDWA | | | | this method is the most validated of any of the |
| compliant free cyanide without distillation. OIA 1677 | | | | cyanide methods in use today. For instance, EPA |
| allows you to obtain results in minutes, not hours. | | | | 335.4 was validated on deionized water samples |
| Many labs use direct colorimetry to measure free | | | | spiked with potassium cyanide. No other method, |
| cyanide, however, we have presented data proving | | | | other than OIA1677 has been challenged with as |
| that direct colorimetry is ineffective in real world | | | | many interferences or metal cyanide species. |
| samples. | | | | Conclusion |
| Analysis of Total Cyanide in Wastewater | | | | ASTM D7511 is almost identical to OIA1677 and/or |
| The most common cyanide measurement is total | | | | ASTM D6888. A UV digester inserted in the path |
| cyanide. The most common technique, called | | | | irradiates the acidified sample solution liberating total |
| distillation,involves a prolonged boiling of the sample in | | | | cyanide, which then enters the 1677 device. Gas |
| strong acid solution while purging with air. These | | | | diffusion accomplishes the same task as distillation but |
| conditions liberate cyanide ion from metal cyanide | | | | without the complexity. This method does not |
| complexes, convert the cyanide ion to hydrogen | | | | require pyridine barbituric acid or chloramine T. Color |
| cyanide gas, and strip the hydrogen cyanide gas | | | | or turbidity does not interfere. This method that |
| from solution. The purge gas carries the HCN to a | | | | eliminates distillation also eliminates numerous |
| basic absorber solution that traps it as the cyanide | | | | interferences giving you better data. |