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Elaheh Khoddami

Penicillamine is a pharmaceutical of the chelator class. It is used as a form of immunosuppressant in the treatment of
rheumatoid arthritis. Penicillamine is also used as a chelating agent. For example, in cystinuria, a hereditary disorder
featuring formation of cystine stones, penicillamine binds with cysteine to yield a mixed disulfide which is more
soluble than cystine. Isoprenaline or isoproterenol is a catecholamine drug that causes arterial and bronchial dilation,
and is sometimes administered via aerosolization as a bronchodilator to treat bronchial asthma and bronchospasm.
Isoprenaline is used as heart motive in aritmi. Uric acid, the end metabolic product of purine through liver, is present
in urine and blood. UA variations are monitored in body fluids as a powerful indicator for early diagnosis of kidney
The first, we describe simultaneous voltammetric determination of penicillamine (PA) in the presence of uric
acid (UA) using a paste electrode(PE) that is consist of p-aminophenol as a mediator and multiwall carbon
nanotubes with TiO2 nanoparticle for rapid, sensitive, and highly-selective determination. The electrochemical
behavior of the compounds at this modified electrode was studied by cyclic voltammetry (CV), differential
pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). The results indicated that the
chemically modified electrode exhibits efficient electrocatalytic activity in the oxidation of PA which occurs at a
potential of about 530 mV, less positive than that for the unmodified carbon nanotubes paste electrode at pH 6.0.
PA and UA in a mixture can be measured independently from each other with a potential difference of 215 mV
using DPV. The results showed that UA cannot catalysis at a surface of the modified carbon naotubes–TiO2
paste electrode. At pH 6.0, the catalytic peak currents were linearly dependent on PA and UA concentrations in
the ranges 0.4 – 200 μmol L–1 PA and 3.0 – 1000 μmol L–1 UA. Detection limits for PA and UA were 0.1 μmol
L–1 and 1.1 μmol L–1, respectively. The relative standard deviation (RSD%) for 1.2 and 1.5 μmol L–1 PA were
1.6% and 2.1%, respectively, whereas they were 1.5% and 1.1% for 15.0 and 30.0 μmol L–1 UA, respectively.
The kinetic parameters such as electron transfer coefficient, α=0.38 and catalytic reaction rate constant,
Kh=2.58×103 M–1 s–1 were also determined using electrochemical approaches. The diffusion coefficient for PA
at the surface of p-aminophenol-modified carbon nanotubes–TiO2 paste electrode was determined 7.14×10-5 cm2
s−1 . Finally, the sensor was examined as a selective, simple, and precise new electrochemical sensor for the
determination of PA in real samples with application standard addition method in drugs and urine.
Finally, a sensitive and selective electrochemical method for the determination of isoproterenol (ISPT) was
developed by using a ferrocene-multiwall carbon nanotubes paste electrode (FCMWCNTPE). The fabrication of
FCMWCNTPE and its electrocatalytic effect for the electrochemical oxidation of ISPT were investigated by
electrochemical impedance spectroscopy and voltammetric methods. The cyclic voltammetric results indicate
that multiwall carbon nanotubes remarkably enhance the oxidation of ISPT at pH 5.0, which is leading to
considerable improvement of anodic peak current for ISPT, and allow the development of a highly sensitive
voltammetric sensor for determination of ISPT in pharmaceutical and urine samples. It has been found that
under the optimum condition (pH =5.0,) in cyclic voltammetry, the oxidation of ISPT occurred at a potential
about 140 mV less positive than that unmodified carbon paste electrode. The kinetic parameters such as electron
transfer coefficient and catalytic reaction rate constant, were also determined and they were equal.0.75 and
124.05767 M–1 s–1. Finally, differential pulse voltammetry exhibited two wide linear dynamic ranges and a
lower detection limit of 0.07 μmol L-1 for ISPT.
Key Words Penicillamine, Uric acid, Isoproterenol, Multiwall carbon nanotubes paste electrode, TiO2, p-
Aminophenol, Ferrocene.

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Elaheh Khoddami | Prof. Ali A. Ensafi


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