Due to the major negative impact of heavy metal ions toward human health and environment,, even at low concentrations, the development of simple, fast and not expensive detection methods of heavy metals is a major challenge for the scientists. Among the different analytical methods for the analysis of heavy metal ions, the corresponding methods based on electrochemical sensors are discussed in this review, due to their above mentioned advantages. Several types of electrochemical sensors and their analytical applications based on electrochemical methods such as: potentiometry, voltammetry and amperometry, are presented. The electrochemical sensors could revolutionize the field of real-time and on-line environmental analysis, due to their high performances as: low detection limits, a wide linear response range, good stability and reproducibility.
The Schiff base N,N'-(salicylidene)-methylenediamine, known as Salmen in combination with Cr(III) forms at pH = 4.5 a greenish precipitate, which is stable at room temperature but decomposed on heating. The study of the Infrared spectra, Electron Spin Resonance (ESR), X-ray diffraction and thermogravimetry has pointed out that the precipitation form is a complex, while the molar ratio showed that the combination rate of Cr(III): N,N'-bis(salicylidene)-methylenediamine is 1:1. The new complex crystallizes in the triclinic systems. This precipitation reaction can be used as a method for the gravimetric determination of Cr(III) with N,N'-bis(salicylidene)-methylenediamine, known as Salmen The precipitate was dried in vacuum and weighed as C 15 H 13 O 3 N 2 Cr. The overage relative error is ± 0.33%. Salmen can be used in order to precipitate and to recover the chromium from wastewaters consequential to the tanning of natural fells.
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