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The paper describes a sensitive method for simultaneous sensing of morphine (MOR) and diclofenac (DCF). The surface of a MgFe 2 O 4 /graphite paste electrode was modified with multi-walled carbon nanotubes, and the resulting sensor was characterized by cyclic voltammetry, differential pulse voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. The electrode showed an efficient synergistic effect in term of oxidation of DCF and MOR, with sharp oxidation peaks occurring at +0.370 and 0.540 V (vs Ag/AgCl) at pH 7.0. The calibration plot for MOR is linear in the 50 nM to 920 μM concentration range, and the detection limit is 10 nM (at a signal-to-noise ratio of 3). The respective data for DCF are 100 nM to 580 μM, with a 60 nM LOD. The sensor was applied to the determination of MOR and DCF in spiked serum and urine samples, with recoveries ranging between 91.4 and 100.7 %. Graphical abstract A sensitive method for simultaneous sensing of morphine (MOR) and diclofenac (DCF) is described. The surface of MgFe 2 O 4 /graphite paste electrode was modified with multi-walled carbon nanotubes, and the resulting sensor showed an efficient synergistic effect in terms of oxidation of DCF and MOR. The calibration plot for MOR is linear in the 50 nM to 920 μM concentration range, and the detection limit is 10 nM. The respective data for DCF are 100 nM to 580 μM, with a 60 nM LOD.

A sensitive and selective procedure is presented for voltammetric determination of cobalt. The procedure involves an adsorptive accumulation of cobalt pyrogallol red (PGR) complex on stationary mercury drop electrode, followed by cathodic stripping voltammetry measurement of reduction current of adsorbed complex at -1.17 V (vs. Ag/AgCl). The optimum conditions for determination of cobalt include pH 11.0, 35 ?M pyrogallol red, an accumulation potential of -0.9 V (vs. Ag/AgCl) and scan rate 80 mVs-1. The peak current is proportional to the concentration of cobalt over the concentration range of 5.0 to 280 ng mL-1 with a detection limit of 1 ng mL-1 with an accumulation time of 140 s. The method was applied for the determination of cobalt in analytical grade NaCl and water samples. nema

The paper describes a sensitive method for simultaneous sensing of morphine (MOR) and diclofenac (DCF). The surface of a MgFe.sub.2O.sub.4/graphite paste electrode was modified with multi-walled carbon nanotubes, and the resulting sensor was characterized by cyclic voltammetry, differential pulse voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. The electrode showed an efficient synergistic effect in term of oxidation of DCF and MOR, with sharp oxidation peaks occurring at +0.370 and 0.540 V (vs Ag/AgCl) at pH 7.0. The calibration plot for MOR is linear in the 50 nM to 920 [mu]M concentration range, and the detection limit is 10 nM (at a signal-to-noise ratio of 3). The respective data for DCF are 100 nM to 580 [mu]M, with a 60 nM LOD. The sensor was applied to the determination of MOR and DCF in spiked serum and urine samples, with recoveries ranging between 91.4 and 100.7 %.

Copper ferrite−copper oxide (CuO-CuFe2O4) nanoparticles as a semiconductor composite with p–n junction were synthesized by co-precipitation reaction. Then, a novel CuO-CuFe2O4 carbon paste modified electrode was fabricated which displays an effectual electrocatalytic response to the oxidation of acetaminophen (AC) and codeine (CO). A linear range of 0.01–1.5 μmol L−1 and 0.06–10.0 μmol L−1 with the detection limits of 0.007 μmol L−1 and 0.01 μmol L−1 were achieved for AC and CO, respectively. The practical usage of the proposed sensor revealed reasonable results for quantification of AC and CO in biological fluids. [Display omitted] •Copper ferrite−copper oxide nanoparticles as a semiconductor composite with p–n junction were synthesized by co-precipitation reaction.•The structure and morphology of nanocomposite was characterized using XRD, FE-SEM and FT-IR spectra.•CuO-CuFe2O4 carbon paste modified electrode was fabricated which displays an effectual electrocatalytic response to the oxidation of acetaminophen and codeine.•No interference was seen from typical species existing in biological samples which suggest selectivity of the modified electrode for accurate analysis of AC and CO in biological samples.

Copper ferrite-copper oxide (CuO-CuFe O ) nanoparticles as a semiconductor composite with p-n junction were synthesized by co-precipitation reaction. Then, a novel CuO-CuFe O carbon paste modified electrode was fabricated which displays an effectual electrocatalytic response to the oxidation of acetaminophen (AC) and codeine (CO). A linear range of 0.01-1.5 μmol L and 0.06-10.0 μmol L with the detection limits of 0.007 μmol L and 0.01 μmol L were achieved for AC and CO, respectively. The practical usage of the proposed sensor revealed reasonable results for quantification of AC and CO in biological fluids.

Spinel-structured cobalt ferrite (CoFe 2 O 4 ) magnetic nanoparticles (MNPs) were synthesized by a modified chemical coprecipitation method. The MNPs were characterized by X-ray diffraction, field emission scanning electron microscopy and Fourier transform infrared spectroscopy. Then, a doxorubicin sensor was constructed by modifying a carbon paste electrode with multi-walled carbon nanotubes (MWCNTs) and the MNPs. Under optimized conditions, the differential pulse voltammetric response of the modified electrode at a working voltage of 0.46 V vs . Ag/AgCl is related to the concentration of doxorubicin in the 0.05–1150 nM range, with a 10 pM detection limit at a signal-to-noise ratio of 3. Graphical Abstract Fabrication process of MWCNT/CoFe 2 O 4 modified carbon paste electrode for electrocatalytic determination of doxorubicin. a) CPE and b) MWCNT/CoFe 2 O 4 /CPE.

A nanocomposite consisting of NiFe2O4 spinel and multi-walled carbon nanotubes was produced according to citrate sol–gel method. Then, it is coated on the electrodeposited gold nanodendrites modified electrode (NiFe2O4–MWCNTs/AuNDs/GCE), and was utilized to electrocatalyze ethanol oxidation. NiFe2O4–MWCNTs/AuNDs/GCE provides higher active surface area and stability compared to AuNDs/GCE, so that it induced superior current density toward ethanol oxidation about. In fact, the spaghetti-like NiFe2O4–MWCNTs could create –OHads on the electrode, which decreases significantly the adsorption of poisonous intermediate substrates on the surface of gold nanostructures, and consequently amplifies charge transfer kinetic compared to bare GCE during the ethanol oxidation reaction.

Analytical performance of conventional spectrophotometer was developed by coupling of effective dispersive liquid-liquid micro-extraction method with spectrophotometric determination for ultra-trace determination of cobalt. The method was based on the formation of Co(II)–alpha-benzoin oxime complex and its extraction using a dispersive liquid-liquid micro-extraction technique. During the present work, several important variables such as pH, ligand concentration, amount and type of dispersive, and extracting solvent were optimized. It was found that the crucial factor for the Co(II)–alpha benzoin oxime complex formation is the pH of the alkaline alcoholic medium. Under the optimized condition, the calibration graph was linear in the ranges of 1.0–110 μg L⁻¹ with the detection limit (S/N = 3) of 0.5 μg L⁻¹. The preconcentration operation of 25 mL of sample gave enhancement factor of 75. The proposed method was applied for determination of Co(II) in soil samples.

Spinel-structured cobalt ferrite (CoFe.sub.2O.sub.4) magnetic nanoparticles (MNPs) were synthesized by a modified chemical coprecipitation method. The MNPs were characterized by X-ray diffraction, field emission scanning electron microscopy and Fourier transform infrared spectroscopy. Then, a doxorubicin sensor was constructed by modifying a carbon paste electrode with multi-walled carbon nanotubes (MWCNTs) and the MNPs. Under optimized conditions, the differential pulse voltammetric response of the modified electrode at a working voltage of 0.46 V vs. Ag/AgCl is related to the concentration of doxorubicin in the 0.05-1150 nM range, with a 10 pM detection limit at a signal-to-noise ratio of 3.