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OT compounds
Spot samples
1 L water samples (pH adjusted to 2 at the moment of
sampling) were added with an appropriate amount of
a solution of 119Sn -enriched butyltin compounds (an
isotopically enriched solution of MBT, DBT and TBT)
as procedure/quantification standard, and allowed to
equilibrate for 15 min with occasional agitation.
The extraction was performed in a separatory funnel
with at least 2 aliquots (30 ml) of a 0.03% tropolone
solution in dichloromethane (to improve the extraction
efficiency of the monosubstituted species), and the
organic phase was collected through anhydrous
sodium sulphate. The organic phase was evaporated
on a rotary evaporator down to a final volume of 1 ml
at the temperature of 30 °C. The organic extract was
transferred into a vial, added with 2 ml of hexane
and 1 ml of isooctane (as keeper solvent) and then
evaporated almost to dryness under a gentle stream of
nitrogen.The organotin compounds were pentylated by
Grignard reagent and then were extracted twice with 1
ml of hexane.The extract was concentrated and purified
on a silica gel column. After concentration down to 0.5
ml, 1 μl of the final solution was injected for GC-MS-SIM As quality control, SPMD blanks (for the procedure
analysis and organotin quantitative determination was
based on isotope dilution method [5].
For sediments, approximately 1.0 g of freeze-dried
material was taken as sample and extracted with 15 ml
of 0.03% (w/v) tropolone in methanolic solution and 1
ml of concentrated hydrochloric acid. The supernatant
was transferred to a separatory funnel and the
extraction procedure was repeated. After the addition
of the 0.03% tropolone solution in dichloromethane,
the subsequent steps were the same as in the seawater
extraction.
Method limits of detection for seawater (as cations)
were 2.5 ng/l for TBT and 2.0 ng/l for DBT and 1.5 ng/l
MBT. All the analyses were carried out by the same
operator. Method limits of detection for sediment (as
cations) were 1.2 μg/kg for TBT and 1.0 μg/kg for DBT
and 0.8 μg/kg for MBT.
A certified reference material, a coastal sediment
(IRMM BCR 462) and fortified blank seawater samples
(TBT, DBT and MBT spiked at 10 ng/l and 100 ng/l as
cation) were used for validation of the procedures.
The analysis of the reference material (n = 3) showed
a good performance, results overlapped the certified Research & development
values ± their uncertainty and recoveries from fortified
blank seawater samples (n = 5) were: TBT 92 ± 21%,
DBT 87 ± 23%, MBT 82 ± 24% (10 ng/l) and TBT 96 ±
10% DBT 92 ± 13% MBT 86 ± 20% (100 ng/l). The GC-
MS determination was done in a single run for all the
samples including blanks and BCR 462.
Passive samples
After an exposure time of 21 days the collected SPMD
samples strips were washed with acidic (HCl 1%) water
and then stored at -20 C°.
The samples were dialyzed with 150 ml of hexane
(two cycles of 24 hours). The organic phase was
evaporated on a rotary evaporator down to a final
volume of 1 ml at the temperature of 30 °C. The
organic extract was transferred into a vial, added
with 1 ml of isooctane (as keeper solvent) and then
evaporated almost to dryness under a gentle stream
of nitrogen. After that, the samples were treated
as described above for organotin determination,
whereas quantitative determination was based on the
isotope dilution method.
and for the campaign) were analysed in parallel
with the samples. No TBT was found in the blanks
analysed.
The concentration in the seawater has been calculated
with the method and constants described by Harman
et al [6] , where the sampling rate of TBT for the SMPD
was 2.67 l/d.
Results and discussion
The major input of TBT, diuron, irgarol, chlorothalonil
and dichlofluanid into marine systems derives from
anti-fouling paints, but occurrences have been related
also with their use in other human activities (farming
and conservation)[7]. For TBT, diuron and recently
irgarol, EQS values for annual averages (AA-EQS)
and maximum allowable concentrations (MAC-EQS)
have been established in the WFD. Table 1 reports the
EQS values. For chlorothalonil and dichlofluanid EQS
standards are not present but values around 5 -10 ng/l
are in discussion for proposed EQS [8-10].
33EAI Energia, Ambiente e Innovazione 4/2015