Environmental Engineering Reference
In-Depth Information
microwave-assisted extraction. The main advantage of ASE is that it allows
a significant reduction of time and has increased potential for being used
routinely. It is able to treat up to 24 sample at a time generating extracts in
about 10 min, and, therefore carries considerable advantages for routine lab-
oratories. Various extraction mixtures [1 Maceticacidinmethanol,0.5 M
acetic acid in methanol with 0.2%(w
v) tropolone and 1 Macetatebufferin
methanol] were tested with the same ASE settings (five static cycles of 5 min
at 100
◦
C) and coupled to HPLC separation and ICP-MS detection [27]. 0.5 M
acetic acid in methanol with 0.2%(w
/
v) tropolone proved to be the most ef-
ficient extractant. The work compares also the efficiency of the proposed ASE
method with conventional acid extractions (acetic acid—stirring overnight)
and medium polarity organic solvent extraction at acidic pH for the extrac-
tion of both butyl- and phenyl-tin compounds. The best overall extraction
results were always assured by ASE, providing quantitative recovery for all
the six compounds from spiked sediment samples. It has also been demon-
strated that extraction time does not influence recoveries and neither does
it induce degradation reactions, while static extraction temperatures above
110
◦
C do influence the decomposition factors [14, 15, 26]. Together with “iso-
topically labelled” spikes to check for possible degradation or transbutylation
reactions, it is a promising powerful technique.
Isotope dilution with in-house synthesized
116
Sn-enriched organotin stan-
dards was applied to evaluate the efficiency of different extraction reagents in
the GC-ICP-MS analysis of sediment CRMs (PACS-2 and BCR 646). Extractants
of increasing ionic strength, from pure organic solvents to a mixture 1 : 1 with
concentrated strong acids were applied in combination with ultrasonication
and mechanical shaking [44, 45] in the presence as well as in the absence of
tropolone. Extraction conditions like HBr : water (1 : 1) and a methanol : acetic
acid (1 : 3) mixture gave results coinciding with the certified values for all the
three butyltin compounds, while extraction with tropolone in diethyl ether or
simply with HCl proved to be the most efficient for the phenyltin forms.
The use of complexing agents in organotin extraction have proved to be
mandatory on several occasions [27, 28], especially in order to extract the
mono-substituted compounds (MBT, MPhT), which tend to undergo strong
ionic interaction and
/
or surface complexation in complex matrices [28], and
the di-substituted compounds (DBT, DPhT) whereas TBT and TPhT are not
affected at all by the presence of complexing agents like tropolone [46].
Thepresenceof1% oxine (8-quinolinol) complexing agent in the extrac-
tion of organotin compounds from spiked marine sediment under acidic
conditions (various concentrations) with different polar solvents was found
to be necessary to improve the recoveries of organotin compounds. Re-
coveries of 84-100% were achieved for both the phenylated and butylated
compounds. Other methods with acidic conditions and non-polar solvent
mixtures mostly foresee the utilization of tropolone [47] or ammonium
pyrrolidine-dithiocarbamate (APDC) [48] as the complexing agent. A good
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