Environmental Engineering Reference
In-Depth Information
Considering the different steps, including instrumental analysis, extrac-
tion generally accounts for a significant percentage of the total error of an
analytical result, especially in speciation analysis and still much has to be
done to improve extraction efficiencies while assuring species integrity. Sev-
eral articles have been published so far with the aim of outlining an ideal
extraction method for speciation purposes, however, many arrived to the
conclusion that even in the case of two very similar sample types, slight mod-
ifications have to be carried out in the method conditions optimized on one
material, to adjust it to the other. Such a thing as the ultimate extraction pro-
cedure has not been found yet, for none of the species of concern, from any
matrix. Nevertheless, publications do propose methods for groups of sam-
ples, while underlining the sample used for the optimization of the method
parameters.
Recently, the main emphasis of developments in the tin speciation of ma-
rine samples has no longer concentrated on the improvement of method
detection limits, but on speeding up the lengthy sample preparation pro-
cedures and tracing the transformation
degradation of organotins that may
occur during the sample treatment steps. In this context, recent developments
in the field of sample preparation for speciation analysis have experienced
a steady shift from traditional technologies. The novel approaches prefer
(i) significant reductions in the use of organic solvents to decrease occupa-
tional hazards and problems of toxic chemical management; (ii) the appli-
cation of isotopically labelled compounds to trace species-specific recoveries
and alteration in the original speciation by degradation and
/
or possible oc-
currence of accidental species transformations such as transalkylation; (iii)
miniaturization that allows easier in-situ and on-site manipulation; and (iv)
the combination of previously well-separated sample preparation steps thus
reducing the overall time required for sample preparation and simplifying the
otherwise complex and time-consuming procedures [11-17].
The materials of marine origin can be divided roughly into three cate-
gories: water, sediment and biological materials. In this chapter the authors
aim to point out the recent applications, and highlight the new developments,
approaches and tendencies within the categories, especially concentrating on
the most challenging step of speciation, the sample preparation methods.
/
2.1
Sample Preparation Methods
for the Determination of Organotin Compounds in Seawater
Organotins are present in seawater at ng L
-1
levels. Their quantification,
therefore, requires highly sensitive techniques, and
/
or the collection of large
sample volumes together with the application of preconcentration methods.
Generally, the applied methods are (i) direct derivatization with organobo-
rates or hydride generation in an acidic medium followed by liquid-liquid
