%0 Journal Article
%T A Voltammetric Sensor Based on NiO Nanoparticle-Modified Carbon-Paste Electrode for Determination of Cysteamine in the Presence of High Concentration of Tryptophan
%A Hassan Karimi-Maleh
%A Maryam Salimi-Amiri
%A Fatemeh Karimi
%A Mohammad A. Khalilzadeh
%A Mehdi Baghayeri
%J Journal of Chemistry
%D 2013
%I Hindawi Publishing Corporation
%R 10.1155/2013/946230
%X A carbon-paste electrode modified with ferrocenecarboxaldehyde and NiO nanoparticle (NiO/NPs) was used for the sensitive and selective voltammetric determination of cysteamine in the presence of tryptophan. The oxidation of cysteamine at the modified electrode was investigated by cyclic voltammetry (CV), chronoamperometry, and square-wave voltammetry (SWV). The values of the catalytic rate constant ( ) and diffusion coefficient ( ) for cysteamine were calculated. The modified electrode exhibits an efficient electron-mediating behavior together with well-separated oxidation peaks for cysteamine and tryptophan. At the optimum pH of 7.0 in a 0.1£¿M phosphate buffer solution, the SWV anodic peak currents showed a linear relationship versus cysteamine concentrations in the range of 0.09¨C300.0£¿¦ÌM and a detection limit of 0.06£¿¦ÌM. Finally, the proposed method was also examined as a selective, simple, and precise electrochemical sensor for the determination of cysteamine in real samples such as urine and capsule. 1. Introduction Cysteamine is a significant thiol drug for the treatment of cystinosis [1]. Since cysteamine therapy has become available for patients with nephropathic cystinosis (MIM219800) in the early 1980s, quality of life for these patients has greatly improved [2, 3]. The most frequent and most severe form, infantile cystinosis, is characterized by the development of renal Fanconi syndrome in the first year of life and leads to end-stage renal disease in the first decade of life when untreated [4]. Mutations in the CTNS gene, encoding for lysosomal cystine transporter cystinosin, are the causes of cystinosis [5]. Lysosomal accumulation of cystine, which is the hallmark of this autosomal recessive disorder, can be depleted by the aminothiol cysteamine [6]. Although treatment with cysteamine substantially decreases intracellular cystine accumulation, renal Fanconi syndrome is not cured, but end-stage renal disease can be postponed in the majority of the patients. Numerous chemical and instrumental techniques for detection of cysteamine have been reported [7¨C11]. Tryptophan (Trp), a vital constituent of proteins and a precursor for biologically important molecules such as the neurotransmitter serotonin and the neurohormone melatonin, is an amino acid essential to humans and animals due to its physiological roles [12]. It is also indispensable in human nutrition for establishing and maintaining a positive nitrogen balance [2]. In previous reports, spectroscopy [13], chemiluminescence [14], capillary electrophoresis [15], high-performance liquid
%U http://www.hindawi.com/journals/jchem/2013/946230/