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Graphite powder-based electrodes have the electrochemical performance of quasi-noble metal electrodes with intrinsic advantages related to the possibility of modification to enhance selectivity and their easily renewable surface, with no need for hazardous acids or bases for their cleaning. In contrast with commercial electrodes, for example screen-printed or sputtered-chip electrodes, graphite powder-based electrodes can also be fabricated in any laboratory with the form and characteristics desired. They are also readily modified with advanced materials, with relatively high reproducibility. All these characteristics make them a very interesting option for obtaining a large variety of electrodes to resolve different kinds of analytical problems. This review summarizes the state-of-the-art, advantages, and disadvantages of graphite powder-based electrodes in electrochemical analysis in the 21st century. It includes recent trends in carbon paste electrodes, devoting special attention to the use of emergent materials as new binders and to the development of other composite electrodes. The most recent advances in the use of graphite powder-modified sol-gel electrodes are also described. The development of sonogel-carbon electrodes and their use in electrochemical sensors and biosensors is included. These materials extend the possibilities of applications, especially for industrial technology-transfer purposes, and their development could affect not only electroanalytical green chemistry but other interesting areas also, for example catalysis and energy conversion and storage.

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The synthesis of the electronic and infrared spectra of di-2-pyridyl ketone salicyloylhydrazone (DPKSH) and di-2-pyridyl ketone benzoylhy-drazone (DPKBH) is reported. Ultraviolet absorption spectra have been applied for determining the dissociation constants: DPKSH, pK1 = 3.5 and pK2 = 6.85; DPKBH, pK1 = 2.75 and pK2 = 10.6. These pK a values are interpreted as a function of the ortho-position of the OH group. Chelating properties of both tridentate ligands have been investigated. DPKSH forms a larger number of metal chelates in acidic media than does DPKBH. Also, it is concluded that DPKSH is a more suitable compound than DPKBH to preconcentrate and to determine heavy metal ion traces as it is inferred from the data obtained by flame AAS.