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.     

Validated ion-exclusion chromatographic method for citrate and acetate in medical fluids

In this paper we describe the development and validation of a solid-phase extraction procedure, followed by ion-exclusion chromatographic determination of citrate and acetate in medical fluids. The medical fluids contained trace levels of non-polar compounds, which were not of interest for the purposes of assay requirements, but due to their strong affinity towards the ion-exclusion chromatography column necessitated a 180-min long runtime to elute. The developed SPE procedure, based on trapping the hydrophobic compounds, on a reversed-phase material, while allowing analytes of interest elute off unretained, shortened the runtime to 35 min. The procedure is simple since it has only two steps, conditioning of the SPE cartridge with acetonitrile and treating the sample. The SPE procedure followed by ion-exclusion chromatographic determination was successfully validated per the International Conference on Harmonization (ICH) guidelines in terms of specificity, accuracy as recovery versus untreated sample, precision, range, linearity of response, ruggedness, stability of treated samples, and robustness. The validation data showed that the method is specific, accurate, precise, rugged, and robust. The validated method has been routinely used in the manufacturing environment.     

Pyrazolines — Derivatives of 2-nitrochalcone

By the reaction of 2-nitrochalcone with hydrazine hydrate, 5-(2-nitrophenyl)-3-phenyl-1H-2-pyrazoline (I) and the hydrazone of 3-(5-(2-nitrophenyl)-3-phenyl-2-pyrazolin-1-yl)-3-(2-nitrophenyl)propiophenol (II) have been prepared. The acylation of both compounds I and II leads to N-acyl derivatives of the first. The acylating ability of formamide and N,N-dimethylformamide was observed in reactions with pyrazoline I. An x-ray structural study was carried out on compound II.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 360–366, March, 1993.     

The reaction of thiocaprylic acid with methyl thiocyanate

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

Mössbauer study of iron reduction in hematite containing mineral originated from Aswan area in Egypt

Mössbauer spectroscopy was used to study iron reduction in mineral originated from Aswan area in Egypt. The Mössbauer spectra of samples heat treated at 1000 °C in hydrogen atmosphere show a gradually reduction process of hematite. The main phase of sample aged for 1 h is magnetite, while alpha-iron as well as some silicates and wustite type oxide can be detected in sample aged for 3 h. Further aging of sample results in dissolution of alloying elements /Si, Al/, being present in the samples. This process starts already in samples aged at 1000 °C for 4 h, but it is more expressive in minerals heat treated at 1200 °C or 1300 °C, when all paramagnetic phases disappeared.     

Acetals of lactams and acid amides. 53. Eamidines in the synthesis of pyridine and pyrimidine

The reaction of -cyano--aminocrotonic ester with DMFA diethylacetal gives 1-ethoxycarbonyl-1-cyano-2-(N-dimethylaminomethylene)-amino-4-dimethylaminobutadiene, the reaction of which with ammonium acetate and amines leads to 4-methylenepyrimidine derivatives. Condensation of -cyano--aminocrotonic ester with dimethylacetamide dieethylacetal gave 2-(ethoxycarbonylcyano)methylene-4-dimethylamino-6-methylpyridine. It was found that in an alkaline medium, 1-benzyl-4-(ethoxycarbonylcyano) methylenepyrimidine recyclizes into 1-benzyl-3-cyano-4-amino-2-pyridone.For Communication 52, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1109–1114, August, 1988.