2. ENVIRONMENTAL ChEMISTRy & TEChNOLOGy 2.1. Lectures

Chem. Listy, 102, s265–s1311 (2008) Environmental Chemistry & Technology
P60 DETERMINATION OF SuLFONAMIDES IN
wATER uSING MuLTI-wALLED CARbON
NANOTubES SPE AND hPLC wITh
FLuORESCENCE DETECTOR
STEFAnIA SIMOn a , DAn LUPU a , ALEXAnDRU BIRIS a
and COnSTAnTIn BELE b
a National Institute for Research and Development of Isotopic
and MolecularTechnologies, R-400293, Cluj-Napoca, Romania,
b University of Agricultural Sciences and Veterinary
Medicine,R-400372,Cluj-Napoca, Romania,
stefania@itim-cj.ro
Introduction
Multi-walled carbon nanotubes (MWCnTs) are a novel
carbon material, repeatedely discussed in the literature for
the solid phase extraction (SPE) of several organic contaminants.
1–3
In this paper a sensitive method was developed for the
determination of six commonly sulfonamides (SAs) in water
by SPE using MWCnTs as adsorbent. Final analysis was carried
out by HPLC coupled with fluorescence detection.
Experimental
R e a g e n t a n d W a t e r S a m p l e s
Sulfadimethoxine (SDM), sulfadiazine (SDZ), sulfamethoxazole
(SMX), sulfamerazine (SMR), sulfanilamide
(SnA), sulfaguanidine (SGn) and fluorescamine were obtained
from Sigma-Aldrich. MWCnTs were purchased from
Institute for Research and Development of Isotopic and
Molecular Technologies Cluj-napoca, Romania. Deionized
and redistilled water was prepared on Milli-Q Plus (Millipore).
Acetonitrile, ortophosphoric acid (H 3 PO 4 ) and dipotassiumphosphate
(K 2 HPO 4 ) were purchased from Merck. A
river water sample was collected from Somes (Cluj-napoca)
and filtered through 0.45 μm nylon membrane and stored at a
temperature of 4 °C.
C h r o m a t o g r a p h i c S y s t e m a n d
C o n d i t i o n s
All experiments were carried out by using Shimadzu VP
Series liquid chromatograph equipped with a degasser and
a mixer of mobile phase. A fluorescence (FL) detector FR-
10 AXL with excitation wavelength of 405 nm and emission
wavelength of 495 nm was used to analyse the tested solutions.
Chromatographic separation was performed on a Alltima
RP C-18 column (250 mm × 4.6 mm, 5 μm). Gradient
elution with a mixture of acetonitrile (solvent A) – phosphate
buffer pH 3.5 (solvent B) at a flow rate of 1 ml min –1 was
applied. The initial gradient conditions were: 65 % solvent B
for the first 25 min, decreasing to 50 % in 25 min, finally it
was brought back to 65 % in 5 min and held for 5 min until
the next injection.
s452
E x t r a c t i o n P r o c e d u r e
The cartridge packed with 200 mg MWCnTs was prepared
in a 6ml polypropylene syringe and the sorbent was
retained by two polyethylene frits. The solutions (water
sample or water sample spiked with analytes) adjusted to
pH 6 were loaded at a flow rate of 4 ml min –1 .Then, SAs
were eluted using a mixture of 3 ml ammonium acetate
water solution (0.2M) and 6 ml acetonitrile.The eluate was
evaporated to about 3 ml under nitrogen stream in a 35 °C
block heater. Then 3 ml of methylene chloride was added and
each samples was mixed and separated. The lower layer was
evaporated to near dryness. The extract was reconstituted in
1.0 ml mobile phase. The analytes were quantified by HPLC
with a pre-column derivatization with fluorescamine (400 μl
of sample + 400 μl of fluorescamine 0.1 %).The whole solution
was mixed with a vortex mixer. The sample was filtered
through a 0.45 μm nylon filter and after standing for 30 min
at ambient temperature was ready for analysis.
Results
The effect of the pH was investigated over the range of
pH 4–8 and it was found that the pH of sample solutions in
the whole range nearly had no influence on the extraction of
SAs.
To investigate the influence of sample volume, different
volumes of pure water were spiked with a constant mass of
0.25 μg of each analyte. It was found that the recoveries of
SAs
decreased slightly with the increase of sample volume. When
the volume was 200 ml, the recoveries of 55–93 % were
obtained for the six SAs.
For elution of SAs we selected a mixture of ammonium
acetate and acetonitrile 1 : 2 (v/v) and better recoveries were
obtained when eluent volume amounted to 9 ml.
The results of the linearity of SAs determined under the
optimized conditions and using 200 ml of spiked pure water
are reported in Table I. The linearity of each compound measured
by HPLC method was good from 0.05 to 5 ng ml –1 .
The correlation coefficient of the calibration curves were
above 0.999.
Table I
Retention time (t R ) and linearity of SAs
Sulfonamide t R [min] b a a b
SMX 11.23 21.694 0.564
SnA 17.69 20.944 0.574
SDZ 20.43 9.402 0.245
SMR 22.94 16.644 –0.192
SGn 42.32 8.021 0.071
SDM 46.68 5.560 0.104
b a : Slope
a b : Intercept
The recoveries of analytes were evaluated using 200 ml
of environmental water samples (Somes river) spiked with