ABSTRACT
The extraordinary prerequisite for the analysis of an anabolic steroid, namely dianabol (DB), has inspired towards the development of a cost-effective and high-performance sensing probe. Thus, a simple and robust electrochemical sensor (c-MWCNTs-Nafion®lGCE) for dianabol (DB), a widely used steroid, was developed using a glassy carbon electrode (GCE) modified with functionalized carboxylated multi-walled carbon nanotubes (c-MWCNT) and Nafion®. At pH 7 - 8, differential pulse-cathodic stripping voltammetry (DP-CSV) displayed two cathodic peaks at -0.85 and -1.35 V that varied linearly over a wide range (9.0 × 10-9 (2.7 µg L-1) - 9.0 × 10-6 (2.7 × 103 µg L-1) mol L-1) and 2.9 × 10-6 (8.7 × 102 µg L-1) - 8.0 × 10-5 (2.4 × 104 µg L-1) mol L-1) of DB concentrations, respectively. The low limits of detection and quantification at peak I (-0.85 V) were 2.7 × 10-9 (8.1 × 10-1 ng mL-1) and 9.0 × 10-9 (2.7 ng mL-1) mol L-1, respectively. The repeatability and reproducibility displayed relative standard deviations lower than 5%. The method was applied for DB analysis in human urine and subsequently compared with the standard HPLC method. Interference of common metabolites in biological fluids samples to DB sensing was insignificant. This method has distinctive advantages e.g. precise, short analytical time, sensitive, economical, reproducible and miniaturized sample preparation for DB analysis in biological samples of human origin.
Subject(s)
Methandrostenolone , Nanotubes, Carbon , Electrodes , Fluorocarbon Polymers , Humans , Reproducibility of ResultsABSTRACT
A unique network core-shell hybrid design-based cross-linked polyaniline (CPA), which was coated with CuO nanoparticles (NPs) and decorated with nitrogen-doped SWCNT/GO/cellulose N-SWCNTS-GO-CE, has been fabricated using the oxidative polymerization technique. This hybrid nanocomposite shows excellent photocatalytic degradation and an acceptable adsorption capability for Methyl Orange (MO) dye in aqueous solutions with a very slight effect for the N-SWCNTS-GO-CE CuO component. The prepared nanocomposites were used for the removal of a carcinogenic and noxious dye, Methyl Orange, from aqueous samples under various adsorption conditions. Approximately 100% degradation of 10 mg/L of Methylene orange dye was observed within 100 min at pH 6.0 using 50 mg/L CPA/N-SWCNTS-GO-CE/CuO nanocomposite under UV radiation. Additionally, significant factors were investigated on the degradation process including the contact time, MO initial concentration (Ci), solution pH, and dosage of the CuO nanocomposite. All investigated experiments were performed under UV radiation, which provided significant data for the MO degradation process. Furthermore, the recovery of the nanocomposite was studied based on the photocatalytic process efficiency. The obtained data provide the high opportunity of reusing CPA/N-SWCNTS-GO-CE/CuO nanocomposite for numerous photocatalytic processes. The CPA/N-SWCNTS-GO-CE/CuO nanocomposite was prepared via chemical oxidative copolymerization of polyaniline (PANI) with p-phenylenediamine (PPDA) and triphenylamine (TPA) in the presence of N-SWCNTS-GO-CE and CuO NPs. The morphology, structure and thermal properties of the CPA/N-SWCNTS-GO-CE/CuO nanocomposite were investigated using various techniques, including FTIR, XRD, RAMAN, SEM, MAP, EDX, TEM, TGA and DTG. Therefore, CPA/N-SWCNTS-GO-CE/CuO nanocomposite can be effectively used as a convenient and reusable adsorbent to remove hazardous dye from wastewater.
ABSTRACT
A simple methods have been developed for determination of Cu(II) ions in aqueous solutions. The spectrophotometric method relied mainly on the reaction between Cu(II) ions and the azo dye ligand named N-diaminomethylene-4-(2,4-dihydroxy-phenylazo)-benzenesulfonamide (H2L) at pH 10.0. The influence of parameters such as concentration, pH and reaction time were inspected. A linear relationship (R2 = 0.9992) between absorbance and the concentration of Cu(II) was obtained at themaximum absorptionpeak of 474 nm within 1.6-9.6 × 10-6 mol L-1 concentration range. The limit of detection for Cu(II) ion and limit of quantitation were 1.1 × 10-7 mol L-1 and 3.7 × 10-7 mol L-1, respectively.The potentiometric method is based on a novel poly(vinyl chloride) membrane, containing the synthesized azo dye as an ionophore, was used to developed a Cu(II)- selective sensor. This newly developed sensor revealed a Nernstian response over Cu2+ ion in a concentration range 1.0 × 10-6-1.0 × 10-2 mol L-1 with cationic slopes of 29.5 ± 0.2 mV decade-1 and detection limits of 3.0 × 10-6 mol L-1 copper(II) for o-nitrophenyl-octyl ether (o-NPOE) based membrane sensor. The electrode showed good discrimination toward Cu2+ ions with respect to most common cations. The advantages of the proposed methods are their simplicity, selectivity, and high sensitivity. In addition, the sensor has been used as indicator electrode in the potentiometric titration of Cu2+ ion against EDTA. The structure and geometry of the complex formed between Cu(II) and H2L ligand was identified via isolation of the solid complex; Co(II) an Ni(II) complexes were synthesized as well. The geometrical structure around the metal centers were proved to be square planar for Cu(II) complex and tetrahedral for Co(II) an Ni(II) complexes.
ABSTRACT
Nanocomposites (NCs) of crosslinked polyaniline (CPA)-coated oxidized carbon nanomaterials (OXCNMs) were fabricated as a very sensitive and simple electrochemical sensor to be utilized in 2,4-dichlorophenol (2,4-DCPH) detection. CPA/OXCNMs NCs were prepared by chemical copolymerization of polyaniline with triphenylamine and p-phenylenediamine in the presence of OXCNMs. The CPA/GO-OXSWCNTNCs exhibited a higher affinity for the oxidation of chlorophenols compared to the glassy carbon electrode (GCE), CPA/GCE, and other NCs. Cyclic voltammetry was performed to investigate and assess the electrocatalytic oxidation of 2,4-DCPH on the modified GCE. The compound yielded a well-defined voltammetric response in a Britton-Robinson buffer (pH 5) at 0.54 V (vs. silver chloride electrode). Quantitative determination of 2,4-DCPH was performed by differential pulse voltammetry under optimal conditions in the concentration range of 0.05 to 1.2 nmol L-1, and a linear calibration graph was obtained. The detection limit (S/N = 3) was found to be 4.2 nmol L-1. In addition, the results demonstrated that the CPA/GO-OXSWCNTs/GCE sensor exhibited a strong anti-interference ability, reproducibility, and stability. The prepared CPA/GO-OXSWCNTs/GCE sensor was used to rapidly detect 2,4-DCPH with a high degree of sensitivity in fish farm water with proven levels of satisfactory recoveries.
