Optical waveguide sensors in analytical chemistry: today’s instrumentation, applications and trends for future development

Current concepts for chemical and biochemical sensing based on detection with optical waveguides are reviewed. The goals are to provide a framework for classifying such sensors and to assist a designer in selecting the most suitable detection techniques and waveguide arrangements. Sensor designs are categorized on the basis of the five parameters that completely describe a light wave: its amplitude, wavelength, phase, polarization state and time-dependent waveform. In the fabrication of a successful sensor, the physical or chemical property of the determined species and the particular light wave parameter to detect it should be selected with care since they jointly dictate the sensitivity, stability, selectivity and accuracy of the eventual measurement. The principle of operation, the nature or the detected optical signal, instrumental requirements for practical applications, and associated problems are analyzed for each category of sensors. Two sorts of sensors are considered: those based on direct spectroscopic detection of the analyte, and those in which the analyte is determined indirectly through use of an analyte-sensitive reagent. Key areas of recent study, useful practical applications, and trends in future development of optical waveguide chemical and biochemical sensors are considered.     

Catalysis by Heterogenized Metal Polymers: Advances and Prospects

The current status, trends, and a specific role for macroligands in catalysis by heterogenized metallopolymeric complexes are considered. Relations between homogeneous catalysis, enzyme catalysis, and catalysis by heterogenized metal complexes are traced. The effects of various factors on the catalysis of the main reactions used in organic synthesis—hydrogenation, polymerization (in particular, under the action of immobilized metallocene and postmetallocene catalysts), and redox processes (such as the catalysis of oxygenation, hydroperoxide oxidation, epoxidation, and hydroformylation)—are analyzed. In this review, attention is focused on the nondestructive identification of intermediates and catalytically active species in heterogenized systems. Experimental evidence is presented in support of the fact that the high activity, stability, and selectivity of immobilized catalysts are associated with a dramatic inhibition of concerted reactions in the coordination sphere of a transition metal, which result in catalyst deactivation, as well as with substrate enrichment. Prospects for the development of these highly organized hybrid systems and possibilities to consider the main requirements imposed on metal complex catalysis even at the stage of designing them are predicted.     

Reactions of Carboxymethyl Polysaccharides and Their Ethyl Esters with Amines

The reaction of carboxymethyl polysaccharides and their ethyl esters with amines was studied with the aim to determine how the structure of the polymeric acylating agent affects the composition of the reaction products.     

Structure of the product of the reaction of 6-dehydroeldelidine with sodium in liquid ammonia

Institute of the Chemistry of Plant Substances, Uzbek SSR Academy of Sciences, Tashkent. Abu Ali ibn Sina [Avicenna] Tashkent State Medical Institute, Dushanbe. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 279–281, March–April, 1990.     

Mass spectrometric study of mixed fluorinated rare earth element β-diketonates with triphenylphosphine oxide

A series of new adducts of fluorinated REE -diketonates with triphenylphosphine oxide was synthesized. The paths of their fragmentation under electron impact were investigated. It was shown that in contrast to the complex with 1,1,1,2,2,3,3-heptafluoro-7,7-dimethyloctane-4,6-dione, the complexes of europium with 1-trifluoromethoxy-1,1-difluoro-5,5-dimethylhexane-2,4-dione and 1, 1,1-trifluoro-5,5-dimethylhexane-2,4-dione form dimeric associates in the gaseous phase. The reasons for this difference in the behavior of the complexes and the possible structure of one of the dimers are discussed.Translated from Teoreticheskaya i Eksperimental'naya Khimiya, Vol. 26, No. 2, March–April, 1990.     

The reaction of thiocaprylic acid with methyl thiocyanate

Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2154–2155, September, 1989.