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In this paper, magnesium based materials (Mg and Mg-alloy (AZ91D)) were surface modified using various organic acids (carboxylic and phosphonic), in order to improve corrosion resistance and enhance theirs biocompatibility. Formations of surface layer were performed by tethering by aggregation and growth (T-BAG) method. Organization and bond mode of these layers were examined by Fourier transform infrared spectroscopy (FTIR). Additionally, semiempirical quantum molecular modeling calculation methods were used for getting insight into their structural and electronic properties, as also as corrosion resistance in the physiological solution (Hanks' solution). Corrosion resistance of modified materials were investigated by electrochemical impedance spectroscopy (EIS) in the physiological solution (Hanks' solution) and obtained results reveal a beneficial effect of the modification by forming organic acids self-assembled monolayer (SAM) on the corrosion properties of magnesium based materials, especially layers of octadecylphosphonic acid. The maximum corrosion inhibition efficiency of 87% for magnesium and of 93% for Mg-alloy (AZ91D) are achieved by the formation of octadecylphosphonic acid (ODPA) SAM.

The review highlights the electroanalytical methods used for the determination of the artificial dye Sunset Yellow, one of the most frequently used azo-dyes, with a very wide field of the application during the last two decades. As azo-dyes may have detrimental effects on living organisms, their content in food must be strictly controlled. Despite other analytical methods for determination of azodyes, the electroanalytical methods, especially voltammetric methods, offer many other advantages besides high sensitivity, selectivity, and reproducibility -e.g., less time for sample preparation and determination, low investment and running cost, electrode miniaturization and modifications, as well as use of eco-friendly materials. This critical review focuses on the electrode materials and their modifications since they are the deciding factor for a successful voltammetric determination of Sunset Yellow. In addition to this, the reaction mechanisms for determination and analytical performance are also presented in the paper.

The focus of this work was to develop a simple electrochemical method for the determination of vitamin C (VitC) by using a specially constructed microelectrode made from pyrolytic graphite sheet (PGS). A procedure for quantifying VitC in a real sample was established. VitC shows a single quasi-reversible reaction. The method was optimized, and analytical determination was performed by using cyclic voltammetry and square wave voltammetry for electroanalytical purposes. The obtained results show a linear response of the PGS electrode in a wide concentrations range. For the lower concentration range, 0.18–7.04 µg L−1, the sensitivity is 11.7 µAcm−2/mgL−1, while for the higher concentration range, 10.6–70.4 µg L−1, the sensitivity is 134 µAcm−2/mgL−1, preserving the linearity of 0.998 and 0.999. The second objective was to determine the effect of the addition of five different types of “green” biowaste on plant growth, VitC content, and antioxidant activity in arugula (Eruca sativa L.) using the developed method. After three weeks of cultivation, small differences in growth and large differences in certain nutritional characteristics were observed. The addition of black coffee makes the soil slightly alkaline and causes a significant increase in VitC content and antioxidant activity.

The electrochemical behavior of folic acid (FA), at the electrochemically prepared ex situ bismuth film (BiF) on glassy carbon electrode, clearly indicates electrocatalytic nature of the prepared film toward FA reduction (at -0.55 V). Scanning electron microscopy is used for morphological characterization of the prepared BiF. Accordingly, we establishing an electrochemical procedure based on square wave cathodic stripping voltammetry, preceded by accumulation of FA on the BiF electrode (BiFE). This analytical method is optimized and its analytical performance is presented. This electrode displays a two linear response range: 0.1 to 1.0 μmol L -1 and 1.0-10.0 μmol L -1 with sensitivity of 20.10 μA μmol -1 L and 2.28 μA μmol -1 L, respectively. Developed method was validated in compliance with spectrophotometric method. Excellent recovery and standard deviation obtained with BiFE revealed great analytical potential of the proposed method which was applied for the determination of FA in pharmaceuticals formulation.

Abstract:The low density and good mechanical properties make magnesium and its alloys attractive construction materials in the electronics, automotive, and aerospace industry, together with application in medicine due to their biocompatibility. Magnesium AZ91D alloy is an alloy with a high content of aluminum, whose mechanical properties overshadow the low corrosion resistance caused by the composition of the alloy and the existence of two phases: α magnesium matrix and β magnesium aluminum intermetallic compound. To improve the corrosion resistance, it is necessary to find an effective protection method for the alloy surface. Knowing and predicting electrochemical processes is an essential for the design and optimization of protective coatings on magnesium and its alloys. In this work, the formations of nickel protective coatings on the magnesium AZ91D alloy surface by electrodeposition and chemical deposition, are presented. For this purpose, environmentally friendly electrolytes were used. The corrosion resistance of the protected alloy was determined in chloride medium using appropriate electrochemical techniques. Characterization of the surface was performed with highly sophisticated surface-analytical methods.