How can I make or extract cyanide

imminent danger

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Jim Eaton, Ph.D.
H&E Testing Laboratory
221 State Street
Augusta, Maine 04333
United States

For further information please contact us by email: [email protected]

GC / MS analysis of hydrocyanic acid in water according to EPA method ME 355.01. The mass scan was carried out at m / z = 26, 27 and 29 (internal standard).
PrepBuilder sequence for cyanide detection: With a click of the mouse, all the necessary steps can be compiled quickly, easily and safely from a list of options.

Consumer protection

Cyanides are one of the chemicals that should be handled with special care. Contact with water alone can release the breath poison hydrogen cyanide (HCN) from them. Regardless of this, cyanides are widely used, including in metallurgy and plastics production. The reason is their ability to form compounds with many organic substances and to form stable complexes with metal ions. As a result of their use, cyanides are also found as a problematic environmental load in industrial wastewater. Through leaks, for example in gold and silver mining, they can get into the environment, into surface and groundwater and pollute our most important drinking water reservoirs. To protect consumers and in accordance with applicable standards and regulations, drinking water must be examined for cyanide. The determination by means of headspace (HS) GC / MS ensures compliance with the required limit values ​​and, with suitable automation of the sample preparation, ensures that reproducible measured values ​​are obtained quickly.

Seconds after ingesting only 120 to 250 milligrams of potassium cyanide (KCN) or sodium cyanide (NaCN), the victim is overcome with a nameless horror: breathing is difficult, suddenly becomes impossible and after about a minute he collapses with convulsions. Appropriate medical measures initiated immediately, even if they are taken immediately, rarely change the prognosis: the patient usually dies in minutes from the consequences of acute respiratory paralysis.
KCN ("potassium cyanide") and NaCN are salts of hydrogen cyanide (HCN), the common name of which "hydrogen cyanide" is probably more common. HCN is one of the strongest and fastest-acting poisons. The lethal dose after oral or inhalation intake is one to two milligrams per kilogram of body weight.
Pure hydrocyanic acid (HCN) is a colorless, very volatile liquid (boiling point: 26 ° C) with a characteristic bitter almond odor. But “not all people are genetically able to perceive this smell; In addition, high HCN concentrations numb the olfactory nerves after a short time, ”says Professor Thomas Daldrup, head of forensic toxicology at the Institute for Forensic Medicine at the University of Düsseldorf.
The toxic effect of hydrogen cyanide is based in particular on the reactivity of the cyanide anion (CN-): apart from a few exceptions, it forms stable complexes with gold, silver and most metals. This of course also applies to trivalent iron, which is important for the transport of oxygen in the human organism. Consequence: Cellular respiration is stopped; the oxygen brought in with the blood cannot be used. This process, which ultimately leads to the death of the organism, is called "internal suffocation".
It can be reversed to a certain extent by appropriate therapeutic countermeasures. In addition, humans are able to enzymatically break down small doses of cyanide in the liver and excrete the resulting metabolic products in the urine. “The reason why we can eat apples and pears with stalks and stems without any worries, although small amounts of hydrogen cyanide can be released from their kernels,” explains Professor Daldrup. Bitter almonds, peas and beans also contain so-called cyanogenic glycosides, from which hydrogen cyanide can develop through enzymatic or chemical hydrolysis.

Toxicity depends on the compound

Speaking of which: Not all cyanide compounds are poisonous per se, like potassium hexacyanidoferrate (II). The chemical, also known as yellow blood liquor salt, is a stable complex from which no cyanide is released; it is used in the food industry as a release agent and stabilizer and is approved in the European Union (EU) as a food additive (E536) for use in table salt and table salt substitutes. Potassium hexacyanidoferrate (III) in turn plays a special role in synthetic chemistry and chemical analysis; the additive known as red blood liquor salt is also used in dyeing and as a hardening agent for steel. However, if handled improperly, for example when exposed to extreme heat or the effects of acids, toxic hydrocyanic acid (HCN) can develop from both blood liquor salts, toxicologists point out.
The very easily soluble alkali and alkaline earth cyanides, which are used on a large scale in the extraction of raw silver and gold, prove to be problematic and extremely dangerous. In the course of the "cyanide leaching" process, the precious metals can be extracted as a cyanide complex from the mostly ground silver ore or sand containing gold. Although it is used in a cycle, residues of the highly toxic lye get into the environment and contaminate the soil, surface and groundwater. The worst-case consequences of such a pollution of the environment became evident in January 2000, when thaws and heavy rainfall damaged the cyanide lye collecting basins at the Baia Mare gold and silver mine in Romania: an estimated 100,000 cubic meters of the most toxic wastewater flowed into the river Tisza and killed all life in it up to the mouth of the Danube. “The worst European environmental disaster since Chernobyl,” judged the press.

Detection of cyanide is important for determining water quality

Poisoned waters will eventually regain their equilibrium, thanks to Mother Nature. In the course of an oxidation reaction, cyanides can be broken down into nitrogen and carbon dioxide and rendered harmless. This process is accelerated in the laboratory using sodium hypochlorite (NaOCl) or hydrogen peroxide (H2O2); without human influence it takes a little longer. However, it is important not to take any risks. Even small amounts of cyanides, if they are ingested with food or drinking water, are able to impair human health. The United States Environmental Protection Agency (EPA) has therefore defined limit values ​​(Maximum Contaminant Level, MCL) that must not be exceeded. According to this, the MCL for cyanides is 0.2 milligrams per liter or 200 ppb. According to the TrinkW2001, the maximum load is 0.5 mg / L. If the values ​​are exceeded, the water supplier is required to take measures to protect consumers.

HS-GC / MS as the method of choice

For the detection of soluble cyanide salts in drinking and spring water, the EPA recently developed a method developed by the H&E Testing Laboratory in the US state of Maine based on headspace gas chromatography in connection with mass selective detection (HSGC / MS) for the reference method (ME 355.01) of cyanides chosen in drinking water. "The method can be applied to all forms of cyanides that easily release HCN in an acidic environment," writes Dr. Jim Eaten from the H&S Testing Laboratory in the method specification. The ME355.01 is based on a method preferred by the US Center of Disease Control and Prevention (CDC) for the detection of cyanides in blood, which has been modified for use in drinking water and environmental analysis. In order to quickly get a picture of the actual contamination of drinking water by cyanides and to be able to take suitable measures to protect consumers immediately, the following procedure is preferred by the EPA:
The samples are collected in 40 mL amber glass vials, preserved by adding 1 mL of 1 N NaOH and stored in a dark environment at 4 ° C until analysis. If the sample turns yellow after adding an o-tolidine solution, the sample must be discarded, regardless of this after seven days at the latest. To ensure a quick and reliable analysis, a suitable autosampler should be used for sample preparation. The dual-rail variant of the MultiPurposeSampler (MPS-PrepStation), which is specifically mentioned in the method, has proven to be ideal. With two robotic arms acting independently in all spatial directions, the MPS enables the user to use a liquid syringe, for example for dosing reagents including the internal standard, as well as taking samples in the headspace at the same time. The GC / MS system is a commercially available combination of devices.
Sample preparation: 1 mL of each sample to be analyzed is pipetted into a 10 mL headspace vial, which is then placed in a row by hand on the sample plate of the PrepStation. All further steps are fully automated and conveniently controlled thanks to the GERSTEL MAESTRO software. All required parameters can be compiled from a list of basic work steps with a click of the mouse; the user only needs a sequence table and yet controls the entire system, i.e. MPS, GC and MS. Due to the PrepAhead function, sample preparation and GC / MS analysis can be nested in time so that all samples can be added to the GC column just in time as soon as the previous run has ended.
The MPS adds 50 μL of an aqueous K13C15N solution as an internal standard to the sample, as well as 200 μL ascorbic acid and 200 μL phosphoric acid to release HCN. The vial is then heated to 60 ° C for four minutes before the analytes, drawn from the headspace, are cryofocused in the GC's cold feed system (KAS) at -10 ° C. After about 1.5 minutes, the KAS is heated to a temperature-programmed temperature of 220 ° C and the analytes are transferred to the GC column. The analysis is then carried out on a commercially available GC / MS system, whereby the following conditions must be observed:

GC column:Agilent PLOT-Q column, part # 19091P-Q04 or equivalent
Carrier gas:Helium (1.1 mL / min), constant flow
GC oven:110 ° C (0 min) - 4 ° C / min - 130 ° C (0 min) - 99 ° C / min - 250 ° C (1.79 min)
MS mode:Selected Ion Monitoring (SIM)
Masses:m / z = 29 (internal standard), 27 and 26

A final remark: According to the H&L Testing Laboratory, the ME 355.01 method was tested by three independent laboratories and on different samples (reagent water, water with a high salt concentration, drinking water with a high TOC content) mixed with different amounts of cyanide (50 and 200 ppb) ) applied. "All three laboratories reported results that were within the requirements and thus confirm the exemplary suitability of the method," says Dr. Jim Eaton.