Blog post

Common Sources of Error When Measuring Cyanide

July 8, 2021

Photo by Piotr Arnoldes

Cyanide is a commonly used chemical that has many uses within the industry, including the production of plastics, metal processing, and the manufacture of organic chemicals.  

One well-documented use of cyanide is within the mining industry, where a process known as "cyanidation" is used to extract precious metals such as gold and silver from ore.

The use of cyanide in the mining industry, however, has both benefits and drawbacks.

Decades of research investigating the use of cyanide in mining has proven it to be one of the safest and most economical methods of recovering gold when used at an industrial scale.

But the biggest drawback of using cyanide is the extreme toxicity of the chemical, which can prove fatal to both humans, wildlife, and the environment if not managed correctly.

For the use of cyanide in mining to remain both cost-effective and safe, it is crucial that sufficient levels of cyanide are used, ensuring the mining process is efficient, without using too much at the risk to health of humans or wildlife. Besides, cyanide prices have risen significantly in the last decade, urging miners to be more conscious about its efficient usage.

Therefore, to ensure the correct levels of cyanide are being used within industrial applications, it is crucial that continuous monitoring and analysis of the chemical are taken. However, due to the chemical nature of cyanide and current testing methodologies, it can prove difficult to quantify accurately.

In this article, we will discuss some of the potential problems and sources of errors that you are likely to encounter when measuring cyanide and how to overcome them.

The Difficulties of Cyanide Measurement

The chemical properties of cyanide that make it so effective for mining also make it difficult to quantify accurately.

Coupled with the fact that measurements of cyanide are typically present at parts per million or parts per billion levels, even small errors in quantification can prove problematic to health or efficiency.

Creating a process that measures cyanide concentration accurately and efficiently is difficult, and there are many different sources of potential error.

Errors Associated with Titration

When it comes to determining the concentration of cyanide, silver nitrate titration is one of the most common methods for quantification. The colorimetric titration method of choice uses silver nitrate as the titrant, with the endpoint - and subsequent concentration of cyanide - being determined by a color change.

Although this method is a well-known method of analysis for free cyanide, there are many potential issues that can arise from this traditional method.

Analyst Error

Regardless of how much experience the operator performing a colorimetric titration has, there will always likely be discrepancies from one sample to the next.

Because the determination of cyanide concentration is determined by the subjective nature of color change, this introduces an error that cannot typically be quantified.

Although one operator may be able to reliably produce consistently accurate results, relying on multiple operators, e.g., throughout different shifts on-site, to detect the exact color change is particularly difficult.

Sample Preparation

Performing analysis by titration also requires accuracy when it comes to preparing solutions and reagents that will be used for the titration itself.

If solutions are prepared, such as via a dilution series, the accuracy and precision of the eventual measurements will be heavily dependent on the accuracy of the experiment preparation.

And because the solutions necessary for silver nitration techniques are sensitive to expire, it is vital to prepare them fresh on a regular basis.  

Not only does this step add huge scope for error, it is also costly from a resource and time perspective.

Speed of Analysis

The accuracy of titration results relies heavily on samples being processed as quickly as possible.

Delays in transferring a sample from site to lab increase the time between sampling and analysis, potentially adding another source of error. This can be further compounded where an operator may have several samples to perform at the same time.

The best scenario is that you can semi-automate any titration method to speed up analysis, but even this requires manual intervention, is likely still too lengthy, and automated titration equipment is known as fragile.

Sample Interference

Complex samples are very tricky Mining samples are very complex in nature and commonly contain many different chemical compounds.

For example, chloride and copper ions also react with the silver nitrate titrant used to quantify cyanide in the same way that cyanide does, and this results in inaccuracies in the measured cyanide concentration.

How Can CyanoGuard Improve Cyanide Measurements?

CyanoGuard cyanide monitoring solution is based on a completely novel and patented technology that helps to overcome the errors associated with traditional free cyanide quantification methods.

One of the main errors associated with titrations is the reliance on operator accuracy and precision. This can come down to operator bias but can also be impacted by the nature of the reagents and the time it takes from sampling to measurement.

Even complex sample matrices that contain compounds that are known to interfere with titration methods are no longer a problem, and results can be reported with confidence.

CyanoGuard offers a highly standardized method by removing the influence of operator bias resulting in less variation in data. Operating CyanoGuard equipment doesn’t require any specialist training or additional equipment, and the lack of calibration and maintenance means that any operator can use it.

With the additional feature of GPS tracking, it is possible to determine where, and by whom samples were taken, with full traceability history from start to finish.

Eliminate Errors in Your Measurements

Although there are difficulties with measuring cyanide concentrations, it is a necessary and vital task to ensure the efficiency and safety of the cyanidation process.

The challenge with analyzing and quantifying cyanide is a difficult one due to the existing inaccuracies associated with traditional cyanide measurements, combined with the difficulty in testing on-site.

The main sources of errors associated with cyanide quantification come from the sampling and measurement method and can be exacerbated by complex sample matrices.

Understanding your monitoring process and choosing the right method are the most crucial steps to improve your cyanide monitoring process.  For many of our clients, trying our solution in a pilot did the trick. Simple and reliable, it allows accurate measurement of cyanide samples with the use of our handheld device. By reducing the time between sampling and testing, and with no sample preparation required, users can measure, visualize and view results in real-time.

Visit our solutions page to learn more about CyanoGuard. You can also watch our joint webinar with ABB to learn how to understand and optimize your cyanide measurement process or get in touch with with us mining.solutions@cyanoguard.com.

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