2. ENVIRONMENTAL ChEMISTRy & TEChNOLOGy 2.1. Lectures

Chem. Listy, 102, s265–s1311 (2008) Environmental Chemistry & Technology
P11 APPLICATION OF A 6-MERCAPTOPuRINE
FuNCTIONALIZED SORbENT FOR
DIFFuSIVE GRADIENTS IN ThIN FILMS
TEChNIQuE
PAVeL DIVIŠ, ROMAn SZKAnDERA and PETER
MATÚŠ
Brno University of Technology, Faculty of Chemistry, ICTEP
Purkyňova 118, BRNO, 612 00 Czech Republic,
divis@fch.vutbr.cz
Introduction
The diffusive gradients in thin films technique (DGT) 1
is used more than 10 years for determination of kinetically
labile metal species in natural waters, soils and sediments 2 .
However this technique is at the present time validated for
measurement of more than 50 metals, only few attention was
applied to measurement of mercury.
As we reported in our previous studies 3,4 , combination
of agarose diffusive gel together with the sorption gel containing
resin with thiol functional groups is the best choice for
measuring of mercury by DGT. nevertheless, at the present
time there is almost no resin of this type for direct use in
DGT on the market. For DGT, strictly defined size of resin
about 100 μm is used. As the resins available on the market
have particle size about 1 mm, there is need to crush their
particles and separate the required fraction by sieving. This
activity can seriously contaminate the resin or it can change
its properties.
In presented study we try to prepare needful resin by our
self in laboratory. The Iontosorb AV resin (Iontosorb, Czech
Republic) with particle size 50–100 μm was used in advance.
This resin contains free amino group which can be easily diazotated
(Fig. 1.). Resulted diazonium salt can be subsequently
used for raction with specific reagent containing thiol groups.
In this work we used 6-mercaptopurine as this reagent. new
modified Iontosorb AV was characterised in laboratory and
then it was used to prepare sorption gels for DGT technique.
The performance of DGT with modified Iontosorb AV was
then tested in model mercury solution.
Fig. 1. Chemical formula of Iontosorb AV
Experimental
M o d i f i c a t i o n o f I o n t o s o r b A V
R e s i n
Iontosorb AV was modified using diazotation and copulation
reactions 5,6 . The amount of 5 g Iontosorb AV was
washed with hydrochloric acid and then with ultrapure water
to neutral pH. After washing, diazotation was performed at
0–5 °C using 1M solutions of hydrochloric acid and sodium
nitrite. Diazotation was stopped after adding of 40 ml of rea-
s355
gents. Yellow product was filtered out and washed several
time with ultrapure water. Diazonium salt was then placed to
the continuously mixed and cooled reactor containing 3.5 g of
6-mercaptopurine dissolved in 10% (v/w) sodium carbonate.
After 24 h new red-brown product was filtered out, washed
several time with ultrapure water and dryed in exicator.
A n a l y t i c a l C o n t r o l o f n e w
F u n c t i o n a l i s e d R e s i n
Qualitative test was done using an infrared spectroscopy
(Impact 400, nicolet, USA). Infrared spectrum of new functionalized
resin was compared with blank infrared spectrum
of Iontosorb AV.
Fig. 2. Infrared spectrum of Iontosorb AV (1) and new functionalized
resin (2)
Quantitative test of thiol groups was done by iodometric
titration at pH ~ 9. To 50 mg of modified Iontosorb AV, 25 ml
of 0.001M potassium iodine was added, and after 5 min of
shaking and 30 min of standing in the dark, resulted solution
was titrated by 0.001M ammonium thiosulphate.
T e s t i n g o f n e w F u n c t i o n a l i s e d
R e s i n f o r U s e i n D G T T e c h n i q u e
Sorption gels for DGT technique were prepared by
incorporation of modified Iontosorb AV into the agarose gel.
The amount of 0.2 g of modified Iontosorb AV was added to
a hot agarose solution (4% (v/w)) and the hot solution was
casted between two glass plates separated by 0.4 mm plastic
spacers. The disks 2 cm in diameter were cuted out from the
gels after cooling down and washig of the gel sheets.
Diffusive gels were prepared by similar way, the only
one difference was that clear hot agarose solution (3% (v/w))
and 0.8 mm plastic spacers were used.
The agarose sorption and diffusive gels were used to
assembly the DGT unit. Four DGT units were exposed in
a 5 dm 3 beaker containing well mixed 10 μg dm –3 mercury
solution for 3 h to perform basic DGT test. Simultaneously
to the exposition of DGT units, mercury concentration in the
solution was measured by atomic absorption spectrometry
(AMA 254, Altec, CZ).