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This paper describes a novel approach to detect Cd(II) using the combination of the differential pulse anodic stripping voltammetry and magnetic nanoparticle based dispersive solid phase microextraction as an efficient, green and accurate method. Currents of Cd(II) increased linearly in the range from 75 to 2000 ng L−1 Cd(II) with a detection limit of 21.6 ng L−1. The RSD values of 2.6 and 6.0 % for 1.00 and 0.10 μg L−1 respectively showed that proposed method has an acceptable repeatability. Recovery values between 92.3 and 98.6 % showed that this approach can be successfully used for determination of Cd(II) in water samples. [ABSTRACT FROM AUTHOR]

The present paper describes the voltammetric analysis of dipyridamole (DIP) at a cheap, disposable pencil graphite electrode (PGE). The working conditions were optimized with regard to the electrode material and the supporting electrolyte. Cyclic voltammetric investigations emphasized that DIP is irreversibly oxidized at the PGE. The electrode process is pH-dependent and controlled by both diffusion and adsorption. For DIP quantitative determination a differential pulse voltammetric (DPV) method in phosphate buffer solution pH 7.00 was developed. DIP's oxidation peak current varied linearly with the analyte concentration, presenting two linear ranges, namely 5.00 x 10-7 -2.50 × 10-5 M and 2.50 × 10-5 -2.50 × 10-4 M, with detection and quantification limits of 1.21 × 10-7 M and 4.03 × 10-7 M DIP, respectively. The newly developed DPV method using the inexpensive, disposable PGE was successfully applied for the simple and rapid determination of DIP from pharmaceutical formulations. [ABSTRACT FROM AUTHOR]

POxNPs/PGE = Pyruvate oxidase nanoparticles; PGE = Pencil graphite electrode • Prepared and characterized pyruvate oxidase nanoparticles (POxNPs). • Immobilized POxNPs onto pencil graphite electrode to construct improved amperometric pyruvate biosensor. • Biosensor displayed limit of detection as 0.58 μM within a linear working range, 0.001–6000 μM. • Biosensor measured elevated level of pyruvate in sera of heart patients. • Working electrode showed storage stability of 210 days, while being stored dry at 4 °C. This present study was aimed to fabricate a sensitive and improved amperometric biosensor by the nanoparticles of pyruvate oxidase, which were prepared and immobilized covalently onto pencil graphite electrode. The biosensor showed ideal working within 5 s under defined conditions of pH 6.0 and incubation temperature of 30 °C at an applied voltage of -0.1 V. Under standard assay conditions, a linear response was obtained between pyruvate concentration ranging from 0.001 to 6000 μM and current (μA). A lower detection limit (0.58 μM) and an excellent correlation coefficient (R2 = 0.999) with standard spectrophotometric assay was obtained for the present biosensor. Within and between batches of coefficients of variation were calculated and found to be 3.61 % and 3.33 %, respectively. The biosensor was put to continual use for over 210 days. The biosensor was employed for the measurement of pyruvate level in sera of normal healthy individuals and persons suffering from heart disease. [ABSTRACT FROM AUTHOR]

The presented study focuses on the optimum conditions for chemical activation of pencil graphite electrodes (PGE) used in the determination of bisphenol A (BPA). The prepared ethanol–HCl mixture for chemical activation of pencil graphite electrode exhibits better activation factor compared with traditional activation methods like anodizing. The obtained porous and highly conductive surface of PGE can be used as a sensing device. The electrochemical behavior of BPA at the modified sensor was investigated. The effects of pH, accumulation time and sensor activation were examined. In the optimum experimental conditions, adsorptive differential pulse voltammetry was used for determination of BPA, which exhibits a linear calibration graph of Ip versus BPA concentration in the range 1.25 × 10–8 to 1.34 × 10–4 M. The calculated detection limit for S/N = 3 was 1.0 nM. The presented sensor is reusable. The activated PGE was applied for the determination of BPA leached from baby bottles as a real sample using spike method. [ABSTRACT FROM AUTHOR]

In this study, a sensitive voltammetric method for the determination of vanillin in commercial food products was proposed using a pencil lead as an electrode material. In the cyclic voltammograms of vanillin recorded in pH 8.0 Britton Robinson buffer at the pre-oxidized pencil graphite electrode (p-PGE), a sharp peak was observed at about 520 mV (vs. Ag / AgCl electrode) attributed to the oxidation of vanillin. Subsequently, the voltammetric determination of vanillin based on its oxidation at p-PGE was carried out using the differential pulse voltammetry (DPV) technique under optimized conditions. DPV results showed that the oxidation peak current of vanillin increased linearly in the concentration range of 0.5 to 10.0 µM vanillin with a detection limit of 0.16 µM (based on 3Sb). In the final step, this voltammetric method was applied to the determination of vanillin in vanilla syrup samples. Results were in good agreement with the values indicated on the labels of samples. [ABSTRACT FROM AUTHOR]

• Facile preparation of Copper nanostructures on cost-effective pencil graphite substrate. • Copper-silver bimetallic nanostructure preparation by galvanic replacement reaction. • Electrocatalytic studies of dopamine oxidation. • High sensitivity and selectivity for dopamine sensing with very low LOD. • Practical feasibility studies using dopamine hydrochloride injection and urine samples. Herein we report preparation of copper-silver bimetallic nanostructures with excellent electrocatalytic properties. Copper nanostructures were formed by template electrodeposition method while bimetallic nanostructures were prepared by galvanic replacement of copper with silver. Electrocatalytic activity of these nanocatalysts were demonstrated using electroanalysis of dopamine as model analyte. A maximum sensitivity of 1.56 μA/μM/cm2 and a lower limit of detection of 26 nM together with good recovery in real sample analysis provided the practical feasibility of the sensor. In summary, this work demonstrates a facile route for the fabrication of cost-effective bimetallic nanoelectrocatalysts under ambient conditions within a short duration of time. [ABSTRACT FROM AUTHOR]