CARO News

Got Cyanide? CARO at the Forefront of Cyanide Testing

Posted on July 19, 2016

Did you know that cyanide is one of the most commonly used chemicals in the world? Its widespread use and highly reactive nature increases the potential for cyanide to enter the environment. At CARO, we most commonly get requests for cyanide testing from mining clients and environmental consultants working on sites where they are worried about cyanide from manufacturing, combustion and other sources.

We have recently validated new instrumentation for the testing of cyanide that dramatically increases our ability to provide you with the most accurate results for all species of cyanide in water and soil. But first…

What is Cyanide?

Cyanide is a highly poisonous ion consisting of carbon and nitrogen atoms with triple covalent bonds (CN^–). Cyanide binds with the enzyme cytochrome C oxidase. This complex inhibits cellular respiration and energy production, resulting in cytotoxic hypoxia affecting the central nervous system and heart. Death can result from exposure to high concentrations.

Due to its high reactivity, cyanide readily forms metal-cyanide complexes and other organic compounds. From an analytical perspective, cyanide is typically categorized as follows:

• Free Cyanide: CN^–, HCN
• Weak Acid Dissociable (WAD/Available) Cyanide: Weak and moderately strong metal-cyanide complexes of silver, cadmium, copper, nickel and zinc
• Strong Acid Dissociable (SAD/Total) Cyanide: Strong metal-cyanide complexes of iron, cobalt, gold, and mercury.

Exposure can occur via inhalation, drinking water, eating food, and touching contaminated soil.  The chemical composition of cyanide in environmental samples is affected by pH, temperature, trace metal content and the presence of compounds containing sulfur.

Where does Cyanide come from?

• Mining: produced for the mining of gold and silver – helps dissolve these metals and their ores
• Manufacturing: used in the production of nylon and some plastics
• Electroplating: used in metal plating baths, e.g. for brass and bronze
• Natural sources: present in some foods and certain plants, especially in the inedible pits
• Combustion: Cigarette smoke and the burning of synthetic materials
• Miscellaneous: petroleum refining, steel production, specialty chemicals

How is Cyanide analyzed?

Our new, fully automated, state of the art CNSolution^TM 3100 system employs in-line UV digestion, a gas diffusion membrane and an extremely sensitive amperometric detector. This replaces our laborious manual distillation and colorimetric technique.

This methodology is relatively new and is now fully approved by the US EPA. ASTM International has published the following reference methods that are the basis of CARO’s offerings:

1. Free Cyanide: ASTM D7237-15a “Standard Test Method for Free Cyanide and Aquatic Free Cyanide with Flow Injection Analysis (FIA) Utilizing Gas Diffusion Separation and Amperometric Detection (2015)
2. WAD Cyanide: ASTM D6888-09 “Standard Test Method for Available Cyanide with Ligand Displacement and Flow Injection Analysis (FIA) Utilizing Gas Diffusion Separation and Amperometric Detection” (2009)
3. Total (SAD) Cyanide: ASTM D7511-12 “Standard Test Method for Total Cyanide by Segmented Flow Injection Analysis, In-Line Ultraviolet Digestion and Amperometric Detection” (2012)

Why does this Matter?

1. Tenfold decrease in reporting limits – as low as 0.5 µg/L
2. Faster! Results are now available 3 time faster than previous
3. Environmentally friendly – toxic reagents are eliminated
4. Improved selectivity – common interference’s are nearly eliminated

How can CARO help?

We have the expertise to analyze cyanide in air, soil, and water.  Please contact us for information on sampling protocols, provision of containers, pricing, and any other questions you may have. We are always happy to help!