Retention of analgin and anesthesin on sorbents with different polarities: The analysis of bellalgin tablets by high-performance liquid chromatography

The effects of acetonitrile and potassium dihydrogen phosphate concentrations in a mobile phase and the pH of the mobile phase on the retention of analgin (dipyrone) and anesthesin (benzocaine) on Symmetry C18 and Nova-Pak CN HP sorbents with grafted octadecylsilanol and nitrile groups, respectively, were studied. It was found that, under identical conditions, retention on the sorbent with grafted nitrile groups was weaker. A rapid and cost-effective procedure was developed for the determination of analgin and anesthesin in the analysis of Bellalgin tablets.     

Structure,tautomerism, and transformations of β-(3-nitro-2-pyridyl)- and β-(3-nitro-4-pyridyl)pyruvic acid esters

It was shown by means of IR, UV, and PMR spectra that -(3-nitro-2-pyridyl)pyruvic acid esters are practically completely enolized in the crystal state and in solution; ethyl -(3-nitro-4-pyridyl)pyruvate has an enol structure in the crystalline state and in pyridine solution but exists as a mixture of keto and enol forms in low-polarity solvents.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 389–393, March, 1974.     

A new synthesis of ampicillin and related investigations

Quaternization of (S)-α-bromophenylacetic acid amide (8) with hexamethylentetramine (hexamine) preceded with ca. 80% inversion of configuration. Accordingly, starting from the trimethylsilylester of N-(S)-(α-bromo-α-phenylacetyl)-6-aminopenicillanic acid (4) quaternization with hexamine and subsequent hydrolysis afforded N-(R)-α-phenylglycyl-6-aminopenicillanic acid (1, ampicillin). Some other model reactions have been investigated.     

Silicon-29 diffusion-ordered NMR spectroscopy (DOSY) as a tool for studying aqueous silicates

The first use of silicon-29 diffusion-ordered NMR spectroscopy (DOSY) is reported, in a study of the speciation of aqueous silicates.     

Trigonometric polynomials with many real zeros

This is a contribution to the theory of “incomplete trigonometric polynomials”T _n , but mainly for the case when their zeros are not concentrated at just one point, but are distributed in some intervalI whose length is not too large. We begin with the simple theorem that if ∥T _n ∥ ≤ 1 and ifT _n has ≥θn, 0<θ< 2, zeros at 0, thenT _n (t) must be small on the interval |t|<2 arcsin (θ/2). There are similar but more complicated and more difficult to prove results whenT _n has ≥θn zeros onI. These results have the following application: IfT _n →f a.e., and if ∥T _n >∥_∞<-1, thenf vanishes on a set of the circleT whose measure is controlled by lim sup (N _n /n), whereN _n is the number of zeros ofT _n onT. In turn, this has further applications to series of polynomials, to norms of Lagrange operators, and to Hardy classes.     

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.