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MESL Analytical methodology developments





Development of methods for measurement of concentration of trace elements in environmental samples using single collector magnetic sector - based ICP Mass Spectrometry and Atomic Absorption Spectrometry

MESL uses a range of methods for trace element determination in its analytical work. Advanced instrumental techniques such as High Resolution ICP-MS and Atomic Absorption Spectrophotometry are applied to quantify long lived radionuclides and trace elements in marine samples. The ability to measure isotope ratios with ICP-MS allows the use of isotope dilution as a calibration strategy alongside of the more common approaches such as the external calibration and the method of standard addition.


Isotopic Measurements for long lived radionuclides

Most elements show an isotopic variation that is constant in nature (i.e. so far, the measurement precision is not high enough to reveal fractionation-induced variation). Therefore, induced changes in the isotopic composition of a target element can be used for elemental assay using isotope dilution or for studying the physical or (bio- and biogeo-) chemical marine processes that the element of interest is involved in. Of special interest is the isotopic analysis of natural radionucleides or some artificial radionuclides in marine samples for evidence of natural isotope variation or environmental contamination in order to evaluate the sources.


Speciation Analysis in Marine Biota and Sediments

Speciation and identification of the chemical state of elements in environment is indispensable in determination of the chemical behaviour, bioavailability and the influence of the elements on the quality of marine environment. It is important to know the concentration of the most toxic forms of the elements in marine samples instead of their total concentration in order to evaluate the real risks. The work performed in MESL with respect to mercury and tin has been devoted to development of highly sensitive and selective methods for mercury and tin speciation respectively in a wide variety of marine samples. An important part has been participation in various certification campaigns for assessment of the analytical results obtained.


Development of sample preparation methods for trace and ultra-trace analysis in marine samples

The research activities in MESL are focused on the development of methods for sample preparation with a view to subsequent trace and ultra-trace elemental determination by Atomic Absorption Spectrometry and ICP-MS. Various analytical approaches are used, e.g. microwave digestion, solid-phase extraction, solvent extraction, ion exchange in column or batch performance. The methods developed are applied to the determination of the trace element content in marine samples- biota, sediments and seawater.


Analytical developments for compound specific isotope analyses (CSIA)

FID chromatograms of a
mixed hydrocarbon fraction
and their resulting separating
fractions after a molecular
sieve treatment

The compound specific isotope analysis (CSIA) is a powerful tool to characterize the sources of the organic matter by using stable carbon isotopes, but it requires high chromatographic resolution of the individual compounds. Sample preparation techniques involving size exclusion and chromatographic techniques, such as molecular sieves and HPLC, have been developed to reduce the complexity of the environmental mixtures enabling the measurements of carbon isotope ratios on individual compounds. Further technical and chromatographic developments are currently being explored to isolate target organic compounds from potential interferents to improve the accuracy of their carbon isotope ratio.


References:
  • Isolation of neutral and acidic lipid biomarker classes for compound-specific-carbon isotope analysis by means of solvent extraction and normal-phase high-performance liquid chromatography, Journal of Chromatogaphy. A, 1045, 71-84, (2004).
  • Utility of 5 angstrom molecular sieves to measure carbon isotope ratios in lipid biomarkers. Journal of Chromatography A, 1165, 172-181, (2007).