A simple and rapid analytical method of determining Pb and Cd in water samples using an electrochemically pretreated pencil-graphite electrode (EP-PGE) is proposed for the first time in the literature. An electrochemically pretreated pencil-graphite electrode was prepared by performing potential cycling between -0.3 V and 2.0 V in 0.1 mol L HPO solution to improve its ability to electrochemically sense Pb and Cd ions. Square-wave anodic stripping voltammetry (SWASV) was used as the electroanalytical method. The electroanalytical parameters that influence the stripping determination of Pb and Cd were optimized based on experimental results. The magnitude of the peak oxidation current was adjusted in order to optimize the value of each parameter. Applying the resulting disposable electrode under the optimized conditions led to good selectivity and sensitivity in the determination of Pb and Cd ions. Interference from coexisting ions was also investigated. The resulting sensor was successfully tested by applying it to a standard reference water sample. Under the optimized conditions, the limits of detection were 0.46 μg L for Pb and 1.11 μg L for Cd using the electrode. Relative standard deviations (%RSD) were 2.76 for Pb and 2.85 for Cd. The linear working ranges of the electrode for Pb and Cd ion detection were 5-45 μg L and 10-40 μg L, respectively. Graphical abstract Preparation of nanoporous pencil-graphite electrode by cyclic voltammetry and stripping voltammetric screening of Pb and Cd.
Article InfoIn this study, a novel voltammetric method has been developed to determine the amount of boron in soil. 50 soil samples were collected from 5 typical sites of agricultural area. After hot water extraction of available boron in the soil samples, all boron is complexed by addition of Alizarin Red S (ARS) to the extraction solutions.Differential pulse anodic stripping voltammetry was used to determine the amount of the boron complexes. The electrochemical parameters have been optimized according to the experimental results. The optimum scan rate, stirring rate, deposition potential, deposition time and pH values were determined as 5 mVs -1 , 200 rpm, -0.5 V (vs. Ag/AgCl, sat.), 15sec. and 7.5, respectively. An oxidation peak was occurred at the peak potential of -0.45 V for Boron-Alizarin complex. The limit of detection, limit of quantification and linear working range were determined for the voltammetric soil-boron analysis. In addition, the interference effects of coexisting ions were successfully investigated. Comparison of the analytical data for analyzing real samples was carried out between the differential pulse anodic stripping voltammetric method and the Azometine H spectrophotometric method have shown good agreement. A great advantage of voltammetry over the spectrophotometric method is found to be simplicity, selectivity and shortening of the analysis time.
Pencil graphite electrode (PGE) modified with MWCNT and Bi3+ (MWCNT/Bi/PGE) was utilized in simultaneous analysis of Pb2+, Cd2+, and Zn2+. Surface and electrochemical characteristics of MWCNT/Bi/PGE were investigated via SEM, cyclic voltammetry, electrochemical impedance spectroscopy, and FTIR measurements. Even though modification with MWCNT did not improve the electroactive surface area, it significantly decreased the charge transfer resistance. Furthermore, modification with Bi3+ significantly increased the sensitivity. Finally, MWCNT/Bi/PGE exhibited the highest sensitivity and reproducibility compared to PGE and PGE modified with only MWCNT. MWCNT/Bi/PGE provided LOD values of 0.27, 0.43, and 1.63 μg L−1, and linear ranges of 1–80, 5–80, and 10–80 μg L−1 for Pb2+, Cd2+, and Zn2+, respectively. Proposed modification method offers effective electroanalytical performance with low time consumption and cost for the analyst.
A pressure calcimeter was made as an alternative to Scheibler calcimeter which is the conventional method of soil CaCO 3 content analyses. Since the measurement of CaCO 3 content of soil with Scheibler calcimeter is a slow and labor intensive method, the accuracy and presicion of the results are based on labor experience. The pressure calcimeter gives fast and accurate results by eliminating these disadvantages. The measurement of CaCO 3 by pressure calcimeter, as in Scheibler, is done by measuring pressure of CO 2 gas produced from reaction of soil with HCl. The gas pressure, formed by the chemical reaction in a gasproof chamber was measured by a digital manometer on the cap. The results were converted to % CaCO 3 by calculations. Excellent correlation (R 2 =0,998) was obtained in calibration carried out with pure CaCO 3 . 46 soil samples contain CaCO 3 between % 1-30 were analysed by Scheibler calcimeter and the results were compared with pressure calcimeter. It can be concluded that pressure calcimeter has given satisfactory results and can be used as an alternative to conventional Scheibler calcimeter in soil CaCO 3 content analysis.
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