Examination of Firearms Review: 2007 to 2010 - Interpol

EtG in blood samples during putrefaction showed that EtG was very unstable
in blood samples at 30/40 o C without preservatives, but was stable with
addition of potassium fluoride at room temperature [ 513 ]. In another
investigation related to stability of EtG and EtS in urine using several
preservatives, it was found that chlorhexidine, a combination of chlorhexidine,
ethylparabene and sodium propionate, and boric acid proved to be useful
preservatives, while EtG degraded in samples doped with thymol, and addition
of these preservatives did not interfere with the LC-MS/MS analysis [514]. The
presence of microorganisms capable of ethanol production was checked by
fermentation tests and the liver was tested for the presence of EtG. It was
confirmed that there was no EtG formation during bacterial fermentation of
glucose to ethanol [515]. Even though EtS is claimed to be more stable than
EtG, a recent study showed possible bacterial degradation of EtS with high
bacterial density [ 516 ]. Study on post-mortem stability and possible
post-mortem redistribution of CDT, another alcohol marker, found that CDT
remains stable for an appreciable time after death and it is not subject to major
post-mortem redistribution [517].
Embalming and formalin fixation are common, and yet they can create
problems if the only available specimens to be analyzed are formalin-fixed
tissues. In a study of the stability of cocaine in formalin-fixed liver and brain
tissues, it was found that in buffered formalin (pH 7.4) cocaine is hydrolyzed to
benzyolecgonine with half-life time of approximately 7 days, whereas in
unbuffered formalin (pH approximately 3.5) it is relatively stable over a period
of 30 days [518]. Eight drugs (sertraline, paroxetine, citalopram, diazepam,
alprazolam, diphenhydramine, promethazine, and hydrocodone) from four
different drug classes were evaluated to determine the difference between
drug concentrations in clamped and blind stick femoral blood, and it was
concluded that there is no significant difference in the results obtained by these
two sampling methods [519]. The stability of drugs and metabolites in urine
after the addition of NaN3 and/or filtration sterilization using an aseptic
collection kit has been investigated [ 520 ]. In urine that was severely
contaminated with bacteria, there were significant losses of
7-aminoflunitrazepam and nitrazepam, and slight decomposition of MA and
amphetamine at 25 o C. However, such degradation was successfully
suppressed by the use of the kit, though the use of the kit and NaN3 were
preferred for 7-aminoflunitrazepam.
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