Elemental mass spectrometry - a tool for monitoring trace element contaminants in the marine environment
Contents
Introduction
To understand the role and effects of trace elements and their species in marine
ecosystems sensitive techniques are necessary to monitor their distribution
between different environmental compartments. Since the beginning of
industrialisation, anthrophogenic activities such as smelting, energy production,
traffic, corrosion processes and landfill, and natural processes such as
alteration, leaching or volcanism both influenced the specific distribution of
trace elements within the marine environment.
Even though the element concentrations in the water phase are relatively low, as
indicated in Fig. 1, significantly increased concentrations at higher levels of
the food chain can be observed due to biomagnification effects. Especially top
predators such as marine mammals are influenced, and different metal related
effects on their health status have been recently investigated (Kakuschke et al.,
2005[1]). Therefore, precise information on the pattern of trace
elements within the ocean as well as their concentration in selected animal
species is of great importance to understand the related biological
effects.
Challenges
Environmental samples such as seawater, biological fluids or tissues are complex
mixtures. Often, they contain a few highly abundant elements (g l-1 level), which
interfere with the sensitive determination of the remaining less concentrated
elements (ng l-1 level) (Fig. 3). Established methodologies often require complex separation schemes to remove the
interfering matrix compo- nents. Often, they are prone to errors and
contamination, which leads to inaccurate results. Furthermore, most of them do
not allow the simultaneous determination of a set of elements.
Methodology
To overcome these limitations, a method based on elemental mass spectrometry,
namely the collision/reaction cell inductively coupled plasma mass spectrometry
(CC-ICP-MS) has been developed (Fig. 4 and 5). It enables us to quantitatively
determine a set of elements within a sample simultaneously (Leonhard et al.,
2002[2]). Here, an inductively coupled argon plasma is used to dry and to
destroy the sample matrix as well as to generate mainly singly charged element
ions, which makes them detectable by mass spectrometry.
As shown in Fig. 2, ICP-MS allows the determination of nearly all relevant
elements present in the periodic table with outstanding sensitivity and accuracy
(Fig. 6 and 7).
Application fields
Vertical profiles in the Baltic Sea Within an intercalibration exercise, the collision/reaction cell ICP-MS method
has been compared with an analytical method for trace element determination in
seawater, which is based on a complex chemical matrix separation strategy and
atomic absorption spectro- scopy (AAS). For ICP-MS measurements the samples were
only acidified and diluted ten times with ultra pure water. The results of both
methods were in good agreement, which indicates the potential of the developed
methodology for the fast and reliable multi-element analysis of seawater samples.
Metal body burdens in seals
Even though the original collision/reaction cell ICP-MS was developed for trace
element analysis of marine water samples, it is easily adapted to new tasks such
as the determination of metal body burdens of marine mammals. As part of the monitoring of the health status of marine mammals, trace element
levels in blood and tissue samples are under investigation, using ICP-MS for a
reliable multi-element screening. The concentrations of selected elements were measured in fresh whole blood
samples of 80 harbour seals, captured at three different locations of the German
and Danish Wadden Sea.
For essential elements, such as calcium, iron or zink, low variations in the
concentration level (12-25%) were observed due to their homeostatic regulation.
Also no significant relation with gender, age or locality has been observed, and
the levels were in the same order of magnitude as in humans. In contrast, the level of trace elements shows a much wider variation of 30-287%.
Blood levels of these elements were more directly influenced by dietary sources. Furthermore, differences between sampling sites in the North Sea have been
observed and could be explained by geographical variation of differently
contaminated prey. In comparison with other trace elements, especially high
arsenic concentrations have been observed (Griesel et al., 2008[3]).
Outlook
These examples show the potential of elemental mass spectrometry for the
investigation of trace elements in the marine environment. Beside the amount of
an element, also its chemical form (speciation) is of great importance,
especially for its toxicity and, accordingly possible effects in the marine
environment. CC-ICP-MS can be readily combined with chromatographic separation
techniques allowing the investigation of relevant element species such as
organotin, mercury or lead compounds.
References
- ↑ Kakuschke, A., Valentine-Thon, E., Griesel, S., Fonfara, S., Siebert, U. & Prange, A. (2005). The immunological impact of metals in Harbor Seals (Phoca vitulina) of the North Sea. Environmental Science & Technology, 39 (19), 7568-7575.
- ↑ Leonhard, P., Pepelnik, R., Prange, A., Yamada, N. & Yamada, T. (2002). Analysis of diluted sea- water at the ng L-1 level using an ICP-MS with an octopole reaction cell. Journal of Analytical Atomic Spectrometry, 17, 189-196.
- ↑ Griesel, S., Kakuschke, A., Siebert, U. & Prange, A. (2008). Trace element concentrations in blood of harbor seals (Phoca vitulina) from the Wadden Sea. Science of the Total Environment, 392 (2-3), 313-323.
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Please note that others may also have edited the contents of this article.
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Please note that others may also have edited the contents of this article.
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Please note that others may also have edited the contents of this article.
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