Proceedings of the International Cyanide Detection Testing Workshop

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Plasma lactate — elevated plasma
lactate concentrations, resulting from
the shift to anaerobic metabolism,
have been used to assess the severity
of cyanide poisoning in humans
(Baud, Borron et al., 2002)
Thiocyanate is the major metabolite of
cyanide, and a number of sensitive methods
are available for its measurement in biological
fl uids (see Table 2 and Logue, Kirschten et al.,
2005). Thiocyanate can be a good marker for
cyanide exposure because it is non-volatile
and can be analyzed in blood, urine, and saliva.
However, analytical recovery of thiocyanate
from whole blood is not quantitative and
thiocyanate concentrations in blood varied
inconsistently during storage at various
temperatures over a period of two weeks
(Logue, Kirschten et al., 2005). In addition,
thiocyanate may be formed by other modes
of metabolism besides cyanide intoxication or
metabolism (Logue, Kirschten et al., 2005).
These same limitations to measuring
thiocyanate as a marker of cyanide
concentration could equally be true
for other metabolites such as formate and
ATCA. All systems that are developed to
detect cyanide will have to demonstrate that
they can differentiate between background,
endogenous sources of cyanide, and that
their concentrations directly correlate with
external cyanide exposure.
One lab (Logue, Kirschten et al., 2005)
is developing a promising possibility for
cyanide detection by looking at the cyanide
metabolite 2-aminothiazoline-4-carboxylic
acid (ATCA). ATCA is stable for months in
biological samples at freezing and ambient
temperatures (Logue, Kirschten et al., 2005).
The method analyzes synthetic urine and
swine plasma through cyanide derivatization
and subsequent gas chromatography–mass
103
spectrometry (GC–MS) analysis. The study
identifi ed a detection limit of 25 ng/ml. This
lab has also conducted preliminary tests of
this method of fi sh samples (Logue, pers.
com.). However, further research is needed
to verify the background levels of ATCA in
fi sh samples, the metabolic clearance rate of
ATCA in fi sh, and the correlation between
cyanide exposure and subsequent ATCA
concentrations.
Summary
The publication of the Mak et al. (Mak,
Yanase et al., 2005) paper has initiated
a discussion regarding the possibility of
developing an improved cyanide detection
test for marine fi sh. However, it is important
to acknowledge that the detection of cyanide,
cyanide compounds, or cyanide metabolites
in fi sh tissues is quite diffi cult. Once exposed
to cyanide, the fi sh rapidly incorporate and
convert cyanide into thiocyanate (SCN - ).
Shortly thereafter, the thiocyanate is excreted.
The half-life of the cyanide is extremely
short. As a result, detection in the fi sh tissues
will be a factor of the amount of time that
passes before a test can be performed. Mak et
al. (Mak, Yanase et al., 2005) point out that it
may be that detection of total cyanide in fi sh
would occur only under “optimal conditions”
such as extreme cyanide exposure followed by
rapid implementation of a cyanide detection
test.