Proceedings of the International Cyanide Detection Testing Workshop

existing cyanide detection methods used
in fi sh samples. The aim was to answer the
following questions: (1) is the current cyanide
detection method appropriate and effective
and (2) what kinds of improvements can
be done to achieve a higher sensitivity and
accuracy? (Mak, Yanase et al., 2005).
The results indicate that the current method
could not measure cyanide concentration
below 1 × 10 -5 m. However, much lower
cyanide concentration in seawater was
enough to suffocate a 500 g marine food
fi sh (Mak, Yanase et al., 2005). Therefore,
the researchers concluded that the cyanide
detection method currently used was not
sensitive enough for the determination of
cyanide traces in post cyanide-exposed fi sh. In
other words, these results indicate the amount
of cyanide necessary to kill fi sh is well below
the amounts that can reliably be determined
using the existing procedures (Mak, Yanase et
al., 2005).
Ultimately, an effective cyanide detection test
will include the following criteria:
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Sufficient sensitivity to detect low
quantities of cyanide in marine fish
hours and perhaps up to days after
exposure
Ability to distinguish between
background levels of cyanide exposure
versus concentrations resulting from
illegal fi shing practices
Use of technology that is available in
countries where marine fi sh collection
occurs
Ability to detect cyanide exposure
prior to metabolic processing by fi sh
Technology that is possible for use by
non-specialized fi eld staff
Ability to replicate the procedure in
many locations
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Ability for rapid reporting of
results to industry and government
representatives
Affordable costs
The ability to test fi sh at the location
of import country — which could
take place several weeks after original
exposure to cyanide
It may be necessary to develop a hybrid
approach that utilizes a less sensitive screening
method in the fi eld. Field-based test samples
that indicate a positive result for cyanide
use can be followed up with more sensitive
and verifi able lab-based tests done on the
same fi sh sample. The techniques that are
appropriate in the fi eld include colorimetric
and some bioassay procedures. If the test
includes chromatography-related methods
such as gas chromatography and high
performance liquid chromatography/mass
spectrometry, it will be necessary to conduct
this work in a laboratory.
Preliminary Work to Improve Cyanide
Detection in Fish
Mak and Law (Mak, Law et al., 2005)
conducted preliminary experiments to
develop a biosensor system and satisfy the
necessary detection criteria. Their methods
include the pretreatment of cyanide with
cyanide hydrolase and then detection by
spectrophotometric formate sensor. The
researchers report that the system has a
detection limit at 7.3 μmol/l although
theoretically it is possible to increase the
sensitivity of the biosensor by injecting a
larger volume of the pre-incubated sample
(i.e. more formate) into the measuring cell.
The researchers identify the following
advantages of this system over other potential
cyanide detection tests: