Nanoscale secondary ion mass spectrometry
(NanoSIMS) is a dynamic
SIMS technique, which offers high spatial resolution allowing the
mapping of chemical elements at the nanometer scale combined with
high sensitivity. However, SIMS for mercury analysis is a challenging
issue due to the low secondary ion yield and has never been done on
NanoSIMS. The introduction of an rf plasma oxygen primary ion source
on NanoSIMS enabled higher lateral resolution and higher sensitivity
for electropositive elements such as most metals. In this paper, for
the first time, mercury analysis by NanoSIMS was developed applying
the new rf plasma O– ion source. All mercury isotopes
could be detected as Hg+ secondary ions and the isotopic
pattern corresponded to their natural isotopic abundances. Furthermore,
Hg+ detection in HgSe nanocrystals has been investigated
where polyatomic interferences from selenium clusters were identified
and separated by high mass resolution (ΔM/M ≥ 3200). However, in the presence of selenium a
strong matrix effect was observed, decreasing the Hg+ secondary
ion yield. In addition, a detection of Se+ ions was possible,
too. The newly developed method was successfully applied to nanoscale
localization by chemical imaging of HgSe particles accumulated in
the liver tissue of sperm whale (Physeter macrocephalus). This demonstrated the applicability of NanoSIMS not only for mercury
detection in surface analysis but also for mercury mapping in biological
samples.
<p>The biological pathway by which MeHg undergoes detoxifications in some mammals and birds has yet to be fully elucidated. The current understanding is that HgSe nanoparticles (NPs) are formed in vivo as the end point of a detoxification process. Presented, is a contribution to the body of work already present in the field based on recent insights into the existence of HgSe NPs after Hg was detected by NanoSIMS, for the first time, in the liver of a sperm whale that was beached in Ardersier, Scotland. Analysis by NanoSIMS found heterogenous distribution and co-localisation of Hg with other elements including Se and Fe, giving a possible insight into the complex biological mechanism that ends in tiemannite NPs being stored in the livers of whales.&#160;</p><p>&#160;</p><p>&#160;</p>
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