Proceedings of the International Cyanide Detection Testing Workshop

Blennies, which were net-caught and exposed
to cyanide. Both the test and the control
fi sh (not exposed to cyanide) were found to
exhibit cyanide levels of about 300 mg/L
(ppm). Hence, the addition of lead carbonate
to the solution prior to ISE testing did not
eliminate the anomalously high readings.
A second experiment evaluated whether
the high readings might be due to iodide
interference with the ISE. Again, the
experiment was inconclusive. In a third
experiment, test fi sh (4 Caribbean Blue
Chromis, 1 Atlantic Wrasse, and 3 Goldfi sh)
were exposed to cyanide concentrations
ranging from 1.3 to 3.9 ppm CN - for times
ranging from one minute (for the 4 chromis)
to 14 minutes (for a goldfi sh). Readings for
control fi sh (1 wrasse and 2 goldfi sh) not
exposed to cyanide produced higher mV
readings than fi sh exposed to cyanide.
Recent analyses by Ms. Benita Manipula
using the Soundararajan procedure and
cyanide measurements obtained using an
Industrial Test Systems (ITS) colorimetric
Cyanide Reagent Strip TM (Cyanide Test Kit
484003) have also experienced diffi culty in
obtaining reliable measurements of cyanide
concentrations in comparison to known
concentrations of cyanide ion in sodium
hydroxide solution (lacking slurry). The
problem does not appear to be related to
the reliability of the ITS cyanide test strips,
since they have been demonstrated to be
sensitive (down to 0.02 mg/L) and reliable
for measuring cyanide ion concentrations in
water (Battelle 2005).
The most likely explanation for these results
is that organics in the digested tissue solutions
containing sodium hydroxide produced the
anomalous readings both with the ISE and
the ITS test strips. Dr. Frant suggested that
these could be volatile mercaptans from
47
sulfur-containing proteins. Further research
is needed to see whether it is possible to
measure cyanide ion concentrations in
solutions obtained from marine fi sh using
the Soundararajan tissue digestion method. It
does not appear likely that the Soundararajan
procedure can be applied as a fi eld test (Rubec
and Soundararajan 1991, Rubec and Manipula
2008).
Cyantesmo Screening Test
The workshop committee agreed that it
might be possible to digest fi sh samples in
sulfuric acid in a closed container to release
hydrogen cyanide (HCN) from the digested
sample into the atmosphere of the container.
Test strips mounted in the container (such as
near the lid of a jar) might be able to provide
a colorimetric indication for the presence of
cyanide ion. This approach would need further
research and fi eld evaluations. It is likely to
only work near the point of collection in the
exporting countries; where cyanide ion is
most likely to be present in the fi sh at higher
concentrations.
Actually, there are several testing protocols
based on this idea. The American Society
of Testing and Materials (ASTM) published
a screening method (D-5049) for screening
cyanides in waste (ASTM 1990). The protocol
involves adding 5 grams of organic sample
to a sealed vial also containing concentrated
sulfuric acid. Hydrogen cyanide released
from the sample causes a color change
with Cyantesmo paper suspended over the
sample.
A similar screening protocol (Figure 1) is used
by the U.S. Food and Drug Administration
(FDA) to analyze various foodstuffs for the
presence of cyanide-including meat and
vegetables (Flurer et al. 2005). It has been
used to detect cyanide with tuna samples
(both frozen and canned) spiked with cyanide.