Ternary complexes in analytical chemistry-I the niobium-pyrocatechol-sparteine complex

A ternary complex of niobium with pyrocatechol and sparteine has been investigated as a sensitive and selective system for the spectrophotometric determination of niobium. The complex is formed rapidly over a wide range of pH and is stable for several days. It is extracted quantitatively by some organic solvents. The interference from 40 cations and 10 anions has been examined, and synthetic mixtures and niobium ores have been analysed.     

EPR spectroscopy in the analytical chemistry of technetium complexes

Electronic Paramagnetic Resonance (EPR) spectroscopy is used for studying paramagnetic Tc²⁺ and Tc⁶⁺ complexes, respectively. Results of liquid and frozen solution studies are discussed as well as those obtained from single-crystal experiments. Structure and bonding properties are derived from the spectral data.     

Applications of mixed-ligand complexes in analytical chemistry (1966-1972)

A review is given of developments in the understanding and application of mixed-ligand complexes in analytical chemistry.     

Nucleation in analytical chemistry

Precipitation involves two processes, nucleation and subsequent crystal growth. The nucleation process is of extreme importance in determining the number and size of the final crystalline particles. The significance of experimental studies of nucleation is discussed and the need for further research indicated.     

Chemiluminescence in analytical chemistry

Analytical applications based on chemiluminescence are reviewed. Analyses in the gas phase for atmospheric pollutants such as sulphur compounds, ozone and oxides of nitrogen are described. The commonest chemiluminescent systems used in the liquid phase are then discussed. Their applications as indicators in different types of titration are outlined. Determinations of organic and inorganic substances are classified according to their action as oxidant, catalyst or inhibitor. Special applications are described in fields such as forensic science, microbiology, polymer technology, radiation chemistry and flow mechanics.     

Quality in analytical chemistry

Summary In order to enhance the quality of analyticochemical statements it is common practice, to optimize the analytical method. But furthermore it is also necessary to fit the design of the study including sampling procedures and calibrations to the aims of the investigation and its consequences as close as possible. The presentation of results should mention all premises which were not empirically tested. To prevent misinterpretation of the results, their respective field of application should be specified. As regards the characterization of methods, it must be explained whether it is to be valid for a specific analysis series, for a measuring system or for the method as such. Thus, the quality in analytical chemistry is measurable in terms of the scientific nature of the statements; that is in terms of their degree of objective verifiability and in terms of their deduction by recognized methods of all disciplines involved, including statistics.     

Markers in analytical chemistry

The growing use of markers in analytical literature in the 10 years, 1991-2000, is presented and discussed because of their relevance in modern analytical chemistry. The complementary and contradictory aspects of markers and others related words, such as tracer, indicator, index, labelling compound, etc., are clarified. To offer a general overview, several classifications of markers are outlined. The main distinction between markers is their internal or external fitness for purpose. Selected examples are assessed on this basis.     

Ultrasound in analytical chemistry

Ultrasound is a type of energy which can help analytical chemists in almost all their laboratory tasks, from cleaning to detection. A generic view of the different steps which can be assisted by ultrasound is given here. These steps include preliminary operations usually not considered in most analytical methods (e.g. cleaning, degassing, and atomization), sample preparation being the main area of application. In sample preparation ultrasound is used to assist solid-sample treatment (e.g. digestion, leaching, slurry formation) and liquid-sample preparation (e.g. liquid–liquid extraction, emulsification, homogenization) or to promote heterogeneous sample treatment (e.g. filtration, aggregation, dissolution of solids, crystallization, precipitation, defoaming, degassing). Detection techniques based on use of ultrasonic radiation, the principles on which they are based, responses, and the quantities measured are also discussed.     

Sensors in analytical chemistry

Chemical sensorics is an independent domain of modern analytical chemistry. In Germany and Japan, multivolume encyclopedias dedicated to sensors were published. The publication of the nine-volume encyclopedia [1] in Germany was immediately followed by the appearance of the annual publication [2] incorporating additional data available from US. The preparations to publication of the next encyclopedia of sensors are under way now. It san be said with a good reason that chemical sensorics is a well-established sphere which is still under active development. This is specifically a testing ground for novel ideas and novel materials. This issue of Rossiiskii Khimicheskii Zhurnal (Zhurnal Rossiiskogo Khimicheskogo O-va im. D. I. Mendeleeva) is dedicated to chemical and biochemical sensors. It makes readers acquainted with the current state of the art in this sphere and covers various types of sensors. Here, we attempt to outline the general situation in this domain of analytical chemistry.     

Ternary ligand-zinc-hydroxamate complexes

Because of the importance of the hydroxamic acid functional group in zinc protease inhibitors, we have measured the stability constants of the ternary complex LMG, where L is series of tridentate and tetradentate ligands containing amino, carboxylate, pyridyl, and/or imidazolyl groups as enzyme models and G is the guest molecule, acetohydroxamate or N-methylacetohydroxamate. All measurements were determined by pH titration which gave reproducible and reasonable results. A general correlation between binding of LMG and that of LM showed ligands that strongly chelated zinc gave less LMG formation. Surprisingly, no correlation was observed between ligand charge and LMG formation even though the guest, acetohydroxamate, is anionic. The pH value of the maximum formation of the ternary complex is also correlated to the acidity of zinc-bound water; more acidic zinc-bound water results in a maximum ternary complex formation at lower pH value.     

Supramolecular analytical chemistry

A large fraction of the field of supramolecular chemistry has focused in previous decades upon the study and use of synthetic receptors as a means of mimicking natural receptors. Recently, the demand for synthetic receptors is rapidly increasing within the analytical sciences. These classes of receptors are finding uses in simple indicator chemistry, cellular imaging, and enantiomeric excess analysis, while also being involved in various truly practical assays of bodily fluids. Moreover, one of the most promising areas for the use of synthetic receptors is in the arena of differential sensing. Although many synthetic receptors have been shown to yield exquisite selectivities, in general, this class of receptor suffers from cross-reactivities. Yet, cross-reactivity is an attribute that is crucial to the success of differential sensing schemes. Therefore, both selective and nonselective synthetic receptors are finding uses in analytical applications. Hence, a field of chemistry that herein is entitled "Supramolecular Analytical Chemistry" is emerging, and is predicted to undergo increasingly rapid growth in the near future.