Proceedings of the International Cyanide Detection Testing Workshop

Polymeric membrane based ion selective electrodes (ISE)
The American Society of Testing and Materials (ASTM) ISE method is the only approach
that has been widely used to detect cyanide exposure in marine fi shes. The method involves
an acid digestion of the fi sh to liberate hydrogen cyanide gas, and capture of cyanide ions in
sodium hydroxide solution after refl ux distillation. Chemicals must be added to help remove
interfering substances such as chlorine and hydrogen sulfi de. An ISE meter manufactured
by Thermo-Orion, using a membrane made of Agl or Ag 2 S, is then used to analyze cyanide
concentrations, based on its interaction with silver. ISE methods may also work for the
detection of thiocyanate.
Spectrophotometric and fl uorescence methods
Both spectrophotometric and fl uorescence methods require extraction techniques to isolate
cyanide and eliminate interferences from blood. Spectrophotometric methods have been
used for detection of cyanide, thiocyanate and ACTA. One common approach involves
the König dye synthesis to form a cyanide halide that is reacted with an aromatic amine to
produce a glutaconic aldehyde product that is measured in the visible region of the spectrum.
Spectrophotometric methods have adequate sensitivity, but they may lack specifi city due to
interferences from other chemical species commonly present during the analysis of cyanide,
especially thiocyanate and thiosulfate. They also require lengthy preparation times and the
products may be unstable. A number of fl uorometric assays are available to determine
cyanide, which have several advantages over spectrophotometric methods, including a lack of
interference from thiosulfate and greater sensitivity.
Flow injection analysis (FIA)
The FIA method is a simple one with high reproducibility. The approach involves injecting
a sample solution containing the target molecule into a fl ow tube where it reacts with certain
chemicals. When the products reach the detector, the target molecules in the sample are
measured. The user is able to control the measuring conditions precisely and also has the
capability to continuously measure cyanide.
Biosensors for detecting cyanide ion
These methods primarily evaluate chemical reaction products based on the enzyme inhibition
of cyanide, cyanide degrading enzymes, and microbial sensors which measure oxygen uptake
by bacteria, yeast or other microorganisms. Biosensors have a rapid response, high selectivity,
and a pollution free procedure. Most biosensors have the advantages of being portable, low
cost, easy to use, and high selectivity. These methods, however, rely on chemical and physical
procedures that can be slow, complex, and require the use of expensive equipment and
environmental loading reagents. Other limitations of biosensors include degradation of the
biological components that make up these sensors, inconsistent electrochemical signals, and
diffi culty producing suffi cient quantities and activities of enzymes or microbes on which these
sensors depend.
Recently, one group applied a biosensor approach to marine fi shes. Organs of the fi sh were
homogenized with NaOH and a fungal enzyme extract was used to produce formate from
metal-cyanide complexes; the formate was converted using an enzyme to NADH which was
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