Environmental Engineering Reference
In-Depth Information
tion. The method allowed a fast (without a clean-up step for sample intakes
smaller than 500 mg), reliable (as showed by BCR 477 analysis), and sim-
ple determination (no special equipment like ASE, MW, etc. is required) of
organotin compounds in biological samples.
Even though the acid extraction in the presence of a polar solvent is
the most widespread method, leaching with acid and low or non-polar sol-
vents [22, 30, 54-56] and basic digestion with tetramethylammonium hydrox-
ide [18, 38, 57-60] are also utilized with good recovery values and LOD at the
ng g
-1
level for each compound.
Alkaline conditions for organotin extraction are restricted to biotic sam-
ples and even then not applied very often and only with TMAH as the extrac-
tant [18, 38, 57-60]. The concentration of TMAH ranges from 20 to 25%and
is always aided by sonication or agitation. The temperature of the extraction
ranges from 50-60
◦
C and the time of extraction from 1 to 2 hours.
A summary of the most applied extractants, derivatizing reagents, pre-
concentration systems and instrumental techniques in the determination of
organotins in marine biota, derived from literature published after 2000, is
reported in Table 3.
3
The Commonly Applied Instrumental Techniques
for the Determination of Organotins in Marine Samples
A significant number of various instrumental techniques are reviewed in the
literature for the determination of organotin compounds [5, 11, 61-66].
The most commonly applied techniques over the last 20 years have been
based on gas and liquid chromatographic separation followed by different
types of detectors. In the case of gas chromatography, a derivatization step is
necessary prior to the separation, due to the low volatility of the target com-
pounds. The conversion of ionic alkyltins into gas chromatographable species
can be divided into two categories: (a) those based on in-situ hydridization
[with sodium borohydride (NaBH
4
)] or alkylation (with most of all NaBEt
4
and NaBPr
4
) in protic solvents [aqueous or (m)ethanolic environment]; and
(b) those based on the liquid-liquid extraction (LLE) of the ionic organotin
compounds and the following derivatization using Grignard reagents (methyl-
, ethyl-, propyl-, pentyl-, hexylmagnesium chlorides
bromides) in non-protic
solvents [9]. After derivatization a clean-up step is usually necessary unless the
derivatized compounds are directly determined by purge-and-trap analysis or
SPME is utilized to extract the derivatized compounds either from the aqueous
or the gaseous phase prior to the gas chromatographic separation [67].
Methods for the direct analysis of volatile organotin compounds, for ex-
ample, cryogenic trapping, gas chromatography, inductively coupled mass
spectrometry (CT-GC-ICP
/
/
MS) systems [23] are seldom applied.
