XIV
h
International Conference on Molecular Spectroscopy, Białka Tatrzańska 2017
313
T6: P–21
A new method for spectrophotometric determination of the total
content of sulfonamides in milk after preconcentration on magnetic
hypercrosslinked polystyrene
Veronika Tolmacheva
1
, Elena Kochuk
1
, Vladimir Apyari
1
,
Stanislava Dmitrienko
1
, and Yury Zolotov
1
1
Chemistry Department, Lomonosov Moscow State University, Leninskie gory, 1/3, 119991 Moscow,
Russia, e-mail: nikatolm@mail.ru
Sulfonamides (SAs) are an important class of antibacterial drugs used in medicine and
veterinary practice. The extensive usage of these drugs in dairy husbandry, unauthorized
prescriptions, or failure to follow label directions can result in harmful drug residues in animal-
derived food products such as milk. The presence of sulfonamide residues in milk is a great
concern because of their carcinogenic potency and possible role in the development of antibiotic
resistance. To ensure food safety for consumers, some countries have established the maximum
residue limit (MRL) of 100 μg kg
–1
for total SAs and 25 μg kg
–1
for sulfamethazine in edible
animal products including milk (Council Regulation (EEC) No. 2377/90, 1990).
Sulfamethoxazole, sulfamethazine and sulfametoxypyridazine are among the most often
detected SAs in milk
In most cases, residual amounts of SAs in milk are determined by HPLC after a complex
sample preparation, which necessarily involves the step of deproteinization of a sample,
followed by sorption isolation and preconcentration of SAs by the solid-phase extraction. Along
with chromatographic methods for the determination of sulfonamides in food and environmental
objects, in some cases it may be expedient and economically more profitable to use simple and
relatively less expensive methods to determine the total content of these compounds in order to
solve practical problems. A combination of magnetic solid-phase extraction and
spectrophotometry can greatly simplify sample preparation and reduce the cost of analysis.
Here we propose a new approach to estimation of the total content of sulfonamides, based on
their sorption isolation and preconcentration on magnetic hypercrosslinked polystyrene (HCPS),
desorption by acetonitrile and spectrophotometric determination in the acetonitrile eluate by
reaction with p-dimethylaminocinnamaldehyde (DMACA). Sulfonamides and DMACA form
intensely colored products (λ = 540 nm, ε = (3.7–5.1)·10
4
) in acetonitrile media (c
DMAСA
= 5·10
–3
M, с
HCl
= 0.02 M, acetonitrile:water = 95:5). The spectral properties of these products are close
that gives rise to easy estimation of their total content. Sample preparation of milk was carried
out as follows. At the first stage, direct sorption of SAs from milk on the magnetic HCPS under
static conditions was carried out, after that the sorbent was separated from milk using a magnet
and washed with water, and then the analytes were eluted from magnetic HCPS with
acetonitrile.
The results showed that the recoveries of four SAs (sulfamethazine, sulfamethoxazole,
sulfamethoxypyridazine, and sulfachloropyridazine) were in the range of 80–98% with the
relative standard deviations ranging between 3% and 8%. The Lambert–Beer’s law was obeyed
in the range of 0.01–2.0 μg mL
–1
in the eluate. The limits of SAs detection using
preconcentration from 25 and 50 mL of milk were of 0.01 and 0.005–0.006 μg mL
–1
respectively. The proposed method can be recommended as a routine screening method for
quantitation of sulfonamides in milk.
Keywords: spectrophotometry; sulfonamides; milk; magnetic solid-phase extraction;
magnetic hypercrosslinked polystyrene
Acknowledgment
This work was financially supported by the Russian Science Foundation (grant N 14-23-00012).
XIV
h
International Conference on Molecular Spectroscopy, Białka Tatrzańska 2017
314
T6: P–22
Experimental and theoretical investigations of the chemotherapeutic
drug capecitabine
Mihaela Chiş
1
, Alois Bonifacio
2
, Valter Sergo
2
, Călin Căinap
3
,
Vasile Chiş
1
, and Monica Baia
1
1
Faculty of Physics, Babeş-Bolyai University, Kogălniceanu 1, 400084 Cluj-Napoca, Romania,
e-mail: mihaelaioanachis@gmail.com
2
Department
of
Engineering
and
Architecture,
University
of
Trieste,
Via
Valerio
6a,
34127
Trieste,
Italy
3
The Oncology Institute "Prof. Dr. Ion Chiricuţă", Republicii 34-36, 400015 Cluj-Napoca, Romania
Capecitabine (CAP), a prodrug of the anti-metabolites group, is mainly used in treating breast,
gastrointestinal and genitourinary tracts cancers. Its anti-metabolic activity starts as a result of its
conversion to 5-fluorouracil which interferes with the production of new DNA [1]. Considering the
complexity and biological importance of this drug, it is of high interest to have a complete structural
and vibrational characterization of the compound. Such investigations could eventually be the ground
work for detecting and monitoring the compound in more complex systems like body fluids.
CAP molecule consists of a ribofuranose ring, a pyrimidine ring, an amide group and an aliphatic
chain (see Fig. 1). There has been some debate over the exact structure of CAP [2, 3], particularly
over the position of H(37) that is attached either to the N(17) in the amide group (t
1
) or to N(11) in
the pyrimidine ring (t
2
). In order to clarify this aspect, in this study we investigated both possible
tautomers by performing geometry calculations for all the minima found on the PM6 derived PES
both in water and gas-phase.
Moreover, Raman and FT-IR spectroscopic techniques coupled with density functional theory
(DFT) calculations were employed in order to obtain a structural and vibrational characterization of
CAP. Based on the DFT calculations results and the analysis of the vibrational FT-IR and Raman
spectra, we were able to establish the most probable conformation of the molecule and to obtain a
reliable assignment of the experimental bands. These results serve as a preliminary study for the
interpretation of the SERS spectra of CAP, which is crucial for attempting to detect the drug in more
complex solutions like body fluids.
Fig. 1. The B3LYP/6-311+G(2d,p) optimized molecular structures of the two possible tautomers
of CAP in gas-phase.
Keywords: capecitabine; Raman; IR; DFT
Acknowledgment
This work was supported by a STSM Grant from COST Action BM1401. The short-term scientific mission was
accomplished in the Raman4Clinics workgroup from University of Trieste, Italy.
References
[1] C.M. Walko, C. Lindley, Clin. Ther. 7 (2005) 23.
[2] J. Rohlicek, M. Husak, A. Gavenda, A. Jegrov, B. Kratochvil, A. Fitch, Acta. Cryst. 65 (2009) 1325.
[3] M. Malinska, P. Krzeczynski, E. Czerniec-Michalik, K. Trzcinska, P. Cmoch, A. Kutner, K. Wozniak, J.
Pharm. Sci. 103 (2014) 587.
Dostları ilə paylaş: |