Structural study and electrochemical behavior of KPb4‐xCdx(PO4)3 (0≤x≤2) in capturing mercury (II) at graphite electrode

A novel mercury (II) sensor was developed by modifying carbon paste electrode by anion‐deficient apatite. The later was synthesized using solid reaction and characterized with XRD, FTIR, Raman and electrochemical techniques. The refinement results with Rietveld method shows good agreement between the experimental and calculated XRD patterns with satisfactory reliability factors. All experimental variables involved in the differential pulse anodic stripping voltammetric (DPASV) method were optimized to develop a reliable method to measure low concentration of mercury (II). The interference experiments show that Ag (I), Pb (II), Cd (II), Fe (II) and Cu (II) had little or no influence on the Hg (II) signal. Moreover, the prepared electrode revealed good repeatability. The practicability of proposed method for the determination of Hg (II) in fish and seawater samples has shown the satisfactory results

Effect of KNO3 to remove silver interferences in the determination of mercury(II): Application in milk and breast milk samples

Mercury determination was performed at rotating silver electrode (RSE) using square wave voltammetry (SWV) in electrolytic mixture of HCl (0.1 mol L−1) and KNO3 (0.2 mol L−1). The reproducibility, sensitivity and accuracy are good, provided the proper instrumental parameters and supporting electrolyte are used. The relationship between the peak current of mercury(II) and its concentration is linear with regression equation: I(μA) = 0.784 [Hg(II)] + 49.5 (r2 = 0.9878) in the dynamic range from 1.0 × 10−7 to 8.0 × 10−4 mol L−1. The detection limit (DL,3σ) and quantification limit (QL,10σ) were 4.61 × 10−8 mol L−1 and 15.3 × 10−8 mol L−1, respectively. The relative standard deviation (RSD) for seven replicate analysis of a solution containing 5.0 × 10−5 mol L−1 was 2.19%. Possible effects of Cu, Co, Fe, MnO4, Zn, were investigated but did not cause any significant interferences. Immobilization of mercury(II) on the surface of rotating silver electrode obeyed to the Langmuir adsorption isotherm. The calculated ΔG°ads value showed that the interaction between mercury and silver electrodes is mainly controlled by a chemisorption process. This methodology was potentially applied for mercury determination in milk and breast milk samples

Electrochemical impedance spectroscopy measurements for determination of derivatized aldehydes in several matrices

A simple, selective and sensitive electrochemical method is described for the determination of different aldehydes at glassy carbon electrode using electrochemical impedance spectroscopy (EIS). The measurements were performed after their derivatization with 2,4-dinitrophenylhydrazine (DNPH) in acidic medium. The impedance measurements were investigated in the frequency range from 100 mHz to 100 kHz at a potential of 1.0 V versus Ag/AgCl. The Nyquist plots were modeled with a Randle’s equivalent circuit. The charge transfer resistance was identified as the dependent parameter on relevant concentration of aldehydes (determined as their hydrazones). Under the optimized conditions, the linearity was established over the concentration range of 1000–0.05 μmol L−1. The limits of detection (LODs) obtained were from 0.097 to 0.0109 μmol L−1. Finally, the developed method has been applied to the determination of aldehydes in drinking water, orange juice and apple vinegar samples with relative standard deviations (RSDs) < 3.1% and acceptable recovery rate (around of 80%)

Electrochemical behavior study of salicylic acid following azo dye formation with 2,4-dinitrophenylhydrazine: Analytical evaluation

A new simple, accurate and cost-effective chronoamperometry (CA) - based approach coupled with azo coupling reaction has been put forward for quantitative analysis of salicylic acid. The reaction involves a two-step process of oxidation of the 2,4-dinitrophenylhydrazine (DNPH) by potassium iodate to give a 2,4-dinitrophenylhydrazinium cation at 0–5 °C and coupling with salicylic acid (SA) to form red salicylic acid-derived azo dye. Electrochemical impedance spectroscopy, square wave voltammetry and chronoamperometry methods were used to characterize the electrochemical behavior of the salicylic acid-derived azo dye. Studies on different variables affecting the reaction were optimized. Under the optimal conditions, amperometric studies showed that the current response exhibits a wide linearity range from 0.1 to 0.0005 mmol L−1 for SA and the limit of detection and quantification are found to be 0.0001 and 0.0015 mmol L−1 (S/N = 3 & 10) respectively. Therefore, the developed method was successfully applied for routine determination of SA in pharmaceutical samples. Keywords: salicylic acid, Azo coupling, DNPH, Chronoamperometr

Square wave voltammetric determination of diquat using natural phosphate modified platinum electrode

A platinum electrode modified with natural phosphate (NP) was evaluated as an electrochemical sensor for diquat (DQ) in aqueous medium. The electrode was prepared by the deposition of natural phosphate on the platinum surface. Diquat was preconcentrated on the surface of the modified electrode by adsorbing with natural phosphate and reduced at a negative potential in 0.1 M K2SO4 solution. The influence of accumulation time and pH of the electrolytic solution were investigated. The calibration graph obtained under the optimized conditions was linear with a correlation coefficient of 0.9813 at levels near the detection limits up to at least 5.32 × 10−9 mol L−1 with the relative standard deviation (RSD) lower than 3.37%. Interferences by some metals were investigated. Fe, Zn, Cu, MnO4 and Hg apparently affected the peak currents P1 and P2 of diquat. The natural phosphate modified platinum electrode was applied to the determination of diquat in natural water samples. The results indicate that this electrode is sensitive and effective for the determination of diquat

Effect of natural phosphate to remove silver interference in the detection of mercury(II) in aquatic algae and seawater samples

AbstractA silver particles impregnated onto natural phosphate (Ag/NP) was synthesized using reaction in solid state. The obtained powder was characterized by X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM). The (Ag/NP) was used as modifier of carbon paste electrode (CPE) to determine mercury by square wave voltammetry. The calibration graph obtained is linear from 1.0×10−8mol·L−1 to 1.0×10−5mol·L−1 at preconcentration time of 5min, percentage loading of 7%, with correlation coefficient of 0.993. The limits of detection (DL,3σ) and quantification (QL,10σ) were 5.8×10−9mol·L−1 and 19.56×10−9mol·L−1 respectively. The repeatability of the method expressed as relative standard deviation (R.S.D.) is 2.1% (n=8). The proposed method was successfully applied to determine mercury(II) in aquatic algae and seawater samples