Voltammetric Determination of Xanthine with a Single‐Walled Carbon Nanotube‐Ionic Liquid Paste Modified Glassy Carbon Electrode
ABSTRACT Single-walled carbon nanotube (SWNT) and room temperature ionic liquid (i.e., 1-butyl-3-methylimidazolium hexaflourophosphate, BMIMPF6) were used to fabricate paste modified glassy electrode (GCE). It was found that the electrode showed sensitive voltammetric response to xanthine (Xt). The detection limit was 2.0×10−9 M and the linear range was 5.0×10−9 to 5.0×10−6 M. The electrode also displayed good selectivity and repeatability. In the presence of uric acid (UA) and hypoxanthine (Hx) the response of Xt kept almost unchanged. Thus this electrode could find application in the determination of Xt in some real samples. The analytical performance of the BMIMPF6-SWNT/GCE was demonstrated for the determination of Xt in human serum and urine samples.
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ABSTRACT: A novel nanocomposite electrode material constituted of gold nanoparticles (AuNPs), multi-walled carbon nanotubes (MWCNTs) and n-octylpyridinium hexafluorophosphate (OPPF6) ionic liquid was prepared and checked for the development of electrochemical (bio)sensing devices. AuNPs/MWCNTs/OPPF6 paste electrodes with micrometer dimensions (500 μm, i.d.) were constructed and applied to the determination of cortisol and androsterone hormones. Regarding cortisol determination, the microsized paste electrode was used to detect 1-naphtol generated upon addition of 1-naphthyl phosphate as enzyme substrate in the competitive immunoassay between alkaline phosphatase-labelled cortisol and cortisol. Squarewave voltammetry allowed determining the hormone within the 0.1- to 10-ng/mL linear range (r = 0.990) with a detection limit of 15 pg/mL and a EC50 value of 0.46 ± 0.06 ng/mL cortisol. The method was applied to the determination of cortisol in urine and serum samples containing a certified cortisol content. Moreover, a microsized enzyme biosensor prepared by bulk modification of the AuNPs/MWCNTs/OPPF6 electrode with the enzyme 3α-hydroxysteroid dehydrogenase was used for the determination of androsterone through the amperometric detection of reduced nicotinamide adenine dinucleotide. A calibration plot with a linear range between 0.1 and 120 μg/mL (r = 0.993) and a limit of detection of 89 ng/mL were obtained. The biosensor was applied to the analysis of human serum spiked with androsterone at the 250 ng/mL concentration level.Journal of Solid State Electrochemistry 17(6). · 2.28 Impact Factor
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ABSTRACT: Nanotechnology is playing an important role in the development of biosensors. The exclusive physical and chemical properties of nanomaterials make them exceptionally suitable for designing new and improved sensing devices, especially electrochemical sensors and biosensors. Room temperature ionic liquids (RTILs) are salts that exist in the liquid phase at and around 298 K and are entirely composed of ions: a bulky, asymmetric organic cation and usually an inorganic anion but some ILs also has organic anion. ILs have received much attention as a replacement for traditional volatile organic solvents as they possess many attractive properties such as intrinsic ion conductivity, low volatility, high chemical and thermal stability, low combustibility, and wide electrochemical windows, etc. Due to negligible or nonzero volatility of these solvents, they are considered “greener” for the environment in comparison to volatile organic compounds. ILs have been widely used in electrodeposition, electrosynthesis, electrocatalysis, electrochemical capacitor, lubricants, plasticizers, solvent, lithium batteries, solvents to manufacture nanomaterials, extraction, gas absorption agents etc. [1–4]. This review discusses the electrochemical sensors and biosensors based on carbon nanotubes, metal oxide nanoparticles, and ionic liquid/composite modified electrodes. The main thrust of the review is to present an overview on the advantages of use of RTILs along with nanomaterials for electrochemical sensors and biosensors. Consequently, recent developments and major strategies for enhancing sensing performance have been thoroughly discussed.BioNanoScience. 3(3).
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ABSTRACT: A stripping method for the determination of xanthine in the presence of hypoxanthine at the submicromolar concentration levels is described. The method is based on controlled adsorptive accumulation at the thin-film mercury electrode followed by a fast linear scan voltammetric measurement of the surface species. Optimum experimental conditions were found to be the use of 1.0 × 10(-3) mol L(-1) NaOH solution as supporting electrolyte, an accumulation potential of 0.00 V for xanthine and -0.50 V for hypoxanthine-copper, and a linear scan rate of 200 mV second(-1). The response of xanthine is linear over the concentration ranges of 20-140 ppb. For an accumulation time of 30 minutes, the detection limit was found to be 36 ppt (2.3 × 10(-10) mol L(-1)). Adequate conditions for measuring the xanthine in the presence of hypoxanthine, copper and other metals, uric acid, and other nitrogenated bases were also investigated. The utility of the method is demonstrated by the presence of xanthine associated with hypoxanthine, uric acid, nitrogenated bases, ATP, and ssDNA.Analytical Chemistry Insights 01/2014; 9:49-55.