Fróðskaparrit - 01.01.1998, Blaðsíða 67

ORGANOTIN OGIMPOSEX í STRANDARØKINUM í FØROYUM
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rectly without further cleaning for dilution
of the acids and the buffer to the proper
concentrations. The certified reference fish
tissue, NIES No. 11, was obtained from the
National Institute for Environment Studies,
Ibaraki, Japan. All glassware used was
cleaned with acetone (Rathburn, glass des-
tilled grade) and heated to 550°C before
use.
Sample work-up
I -2 g of the biological samples were added
tripentyltinchloride (TPeTCl) as intemal
standard and mixed with ~2 mL of a 10 %
solution of the tissue solubiliser (TEAH in
methanol) to free the organotin compounds
from the matrix: If necessary, water was
added to assure good contact between the
sample and the solubiliser. The samples
were left in the dark ovemight to assure
complete sample decomposition. Sample
pH was adjusted to pH=5 before the de-
rivatisation by adding a few drops of 1 M
HCl and ~2 mL of the acetic buffer (pH=5,
0.5 M HAc). Ar-gas was bubbled through
the sample to remove dissolved oxygen.
Samples were then derivatised by addition
of 0.5 mL aliquots of a 10 % solution of
NaBEt4 in methanol and n-hexane was
added simultaneously to extract the deriva-
t sed, lipofilic species. The samples were
shaken thoroughly and left for 10 minutes
to complete the derivatisation. To further
extract the tetraalkylated organotins the
samples were shaken for another 5 minutes
and centrifuged for 10 minutes at 3500
rpm. The whole process was repeated once
and the combined organic phases were
dried with anhydrous Na2S04. Samples
with high fat content and extracts with
“dark” colour were cleaned by gel perme-
ation chromatography. Before analysis the
samples were evaporated with a gentle
stream of purified nitrogen gas (99.996 %,
AGA) to approximately 100 pL. Blank
samples were included in the procedure for
every sample series (10 samples) analysed.
Clean-up by gel permeation
chromatography
Sample clean-up was performed by gel per-
meation chromatography. Injections were
made by a Waters™ 717 Autosampler
(Milford, MA, USA). A Model 510 HPLC
pump from Waters was used and the sam-
ples were fractionated on two Waters Envi-
rogel TM GPC columns (crosslinked
styrene divinylbenzene), 19 x 150 mm and
19 x 300 mm, coupled in series. Detection
was made by a Model SPD-6A UV-VIS de-
tector (254 nm) connected to a Model SP
4270 integrator from Spectra-Physics (San
Jose, CA, USA). The mobile phase was
dichloromethane (Rathburn, Walkerburn,
Scotland, HPLC glass destilled grade) at a
flow of 5.0 mL/min. The organotin com-
pounds were collected by a Waters Lraction
Collector in the fraction from 75 to 115
mL.
Qualitative and quantitative
organotin analysis
Analysis of organotin compounds was car-
ried out by means of a HP 5921A atomic
emission detector (Hewlett-Packard, Wilm-
ington, DE, USA). The detector was cou-
pled to a HP 5890A gas chromatograph
(Hewlett-Packard) equipped with an HP