Analysis of primary aliphatic short-chain monoamines by LC in water samples

Several derivatization procedures with o-phthaldialdehyde-N-acetylcysteine (OPA-NAC) were compared for a rapid analysis of primary aliphatic short-chain monoamines in water samples by HPLC using a LiChorospher analytical separation column (100RP₁₈ mm i.d., 5 μm). Both the solution and the solid-support assisted off-line derivatization on C₁₈ SPE cartridges were inadequate options because of beginning degradation processes of the instable isoindol derivatives during their transfer to the analytical column. This problem was precluded with the on-column or solid-support assisted on-line derivatization. In the last mentioned procedure, the derivatization took place in a Hypersil C₁₈ precolumn ( mm i.d., 30 μm) connected with an additional preconcentration step resulting in better detection limits (0.002-0.040 μg ml⁻¹ requiring only 150 μl of water sample) than in the on-column procedure (0.08-0.16 μg ml⁻¹). The improved sample handling, the better control of parameters affecting reaction rates, the fully automation of this method with only 10 min analysis time for each sample are further advantageous. The potential of the solid-support assisted on-line derivatization was outlined and applied to water samples from several sources. Recovery values near 100% were obtained.     

Emission studies of pyrene solutions

Emission spectra of pyrene in hexane have been obtained over a temperature range (from 130 to 260 K) that has not been explored before for concentrations ranging from 10^?4 mole/? to 2 × 10^?2 mole/?. A conventional and new approximation which does not depend on the experimental set-up response functions has been used for evaluating pyrene excimer association energy W_DM and other pyrene parameters. In both methods W_DM agrees quite satisfactorlly, at all concentrations used, with that reported in the literature and obtained by other techniques. However, both approximation fail to yield the right values of the rate parameters at concentrations ? 2 g/?. This set the upper limit of sample solubility to be at C = 2g/? for our range of temperature. Furthermore, the new approximation can probably be used at higher concentration (for higher range of temperature) and even may be used for other organic molecules. There was also no difference in the ratio of the excimer (I_D) to monomer (I_M) quantum yields when an intense laser beam was used as a source of excitation rather than a super-pressure Hg-lamp. This suggested that the concentrations we used might not be large enough. As a result, the laser beam would not create enough density of excited molecules to affect the ratio of I_D/I_M.     

One-pot synthesis of 5-(substituted-amino)pyrazoles

An efficient and mild one-pot synthesis of substituted 5-alkylamino and/or 5-(arylamino)pyrazoles is described. A suitably decorated β-ketoamide, an aryl or alkyl hydrazine and Lawesson's reagent are suspended in THF/Py and gently heated to yield the requisite 5-aminopyrazoles.     

DI-2-Pyridyl ketone thiosemicarbazone as an analytical reagent

The synthesis, characteristics and analytical reactions of di-2-pyridyl ketone thiosemicarbazone are described. This compound reacts with iron(II) (λ_max=410mm, ε = 9.3 · 10³ 1 mol^?1 cm^?1), nickel(II) (λ_max =395 mm ε =19.6·10³ 10 mol ^?1 cm ^-1), cobalt(II) (λ_max = 415 nm. ε = 1.0 · 10⁴ mol^?1 cm^?1 ) and copper(I) (λmax =395mm ε = 11.3 · 10³ mol^?1 cm^?1) A critical comparison of di-2-pyridyl ketone, picolinaldehyde and bipyridylglyoxal thiosemicarbazones as analytical reagents is given.     

Reaction of monocyclic ferrocenyl-4,5-dihydropyrazoles with β-dicarbonyl compounds

Monocyclic 3- and 5-ferrocenyl-4,5-dihydropyrazoles with a free NH group in the molecule react with acetylacetone to form the corresponding enaminocarbonyl compounds. The latter were isolated as a single isomer, presumably E. 3-Ferrocenyldihydropyrazoles and 5-ferrocenyl-3-(p-methoxyphenyl)-4,5-dihydropyrazole analogously react with acetoacetic ester. 5-Ferrocenyl-3-phenyl-, 3-(p-bromophenyl)-5-ferrocenyl, and 3,5-diferrocenyl-4,5-dihydropyrazoles react with acetoacetic ester to form acetoacetylpyrazolides.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 12, 2004, pp. 1942–1947.Original Russian Text Copyright © 2004 by E. Klimova, Vazquez Lopez, T. Klimova, Martinez Garcia, Meleshonkova, Ruiz Ramirez.This revised version was published online in April 2005 with a corrected cover date.     

Elemental concentration in the cortex and hippocampus of Wistar rats by X-ray total reflection fluorescence with synchrotron radiation

Summary The study of trace element levels is of great importance due to their relevance in agingand several neurodegenerative diseases. This work compares the elemental concentrations in different postnatal ages and between the temporal cortex, entorhinal cortex and hippocampus from Wistar rats, using X-ray total reflection fluorescence with synchrotron radiation. Ten elements were determined in brain samples: Ti, Cr, Mn, Fe, Cu, Zn, (at trace level) and P, S, Cl and K (at major levels). The elements that increased with aging in cortical areas were: S, K, Fe, Cu and Zn. Ca and Zn levels decreased with advancing age in the hippocampus. In addition to this, Ti, Mn and Fe levels were more conspicuous in the entorhinal cortex.     

Determination of inorganic cations in brine solutions by ion chromatography

The method for analysis of inorganic cations in brine solutions was developed. Ion chromatography is a well-established and accepted technique in the determination of a variety of inorganic ions. However, there are significant complications when ion chromatography is used to determine trace concentrations of inorganic ions in brine matrices. The brine solution in our study was made to simulate the solution from the Waste Isolation Pilot Plant. Instrumental parameters such as eluent composition, flow-rates, and sample loop volumes were investigated to arrive at the optimum condition for the determination of the cations with minimal dilution. Separation was carried out in a Dionex CG12A/CS12A with 8.25 mM H2SO4 as eluent at 1.2 ml/min flow-rate. Our results indicated that ion chromatography is an accurate and a good alternative method for the analysis of cations in brine solution.     

Base promoted transformation on thiadiazolopyridinium chlorides

1,2,4-Thiadiazolo[2,3-a]pyridinium chlorides undergo a very facile base promoted transformation to give bispyridilimino-1,2,4-thiadiazolidines. The unequivocal structural assignment of these last compounds was achieved by spectroscopic ¹H, 13C and ¹⁵N two dimensional methods.     

Signatures andS-discrete lattice-ordered groups

The central theme of this article is the approximation of lattice-ordered groups (l-groups) first by Specker groups and, subsequently, by the so-calledS-discretel-groups. The sense of these approximations is made precise via the notion of a signature, defined below, and by that ofa ^*-subgroups. Sample result: ifG is a projectablel-group then it has anl-subgroupH which is Specker and for which the mapPPH defines a boolean isomorphism between the algebras of polars ofG andH.Presented by L. Fuchs.This article was written while this author was a Stouffer Visiting Professor at the University of Kansas. He wishes to thank the members of the Mathematics Department of that institution for their hospitality.