Binuclear Cu2+ complex mediated discrimination between L-glutamate and L-aspartate in water

L-glutamate and L-aspartate selectivity is achieved by the action of two Cu2+ metal ions rightly disposed in a cyclophane-type macrocyclic framework; electrochemical sensing of glutamate has been achieved by adsorption of the copper complexes on graphite electrodes.     

Ausnützung der Sorptionseigenschaften von Trägern in der Graschromatographie

Zusammenfassung Die Möglichkeit der Anwendung fester Stoffe mit kleinen Oberflächen als Sorbentien in der Gaschromatographie wurde untersucht. Die Sorptionseigenschaften von Trägern auf Kieseiguhrbasis, Rysorb BLK, LM und P wurde geprüft. Rysorb BLK wurde mit Saccharose in verschiedener gewichtsmäßiger Bedeckung modifiziert und der Einfluß des Bedeckungsgrades auf die Trennwirkung des Trägers untersucht. Ferner wurde die analytische Anwendung solcher Träger bewertet.

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Summary The possibility of employing solid materials with small surfaces as sorbents in gas chromatography was investigated. The sorption properties of carriers with a kieselguhr base, Rysorb BLK, LM and P were tested. Rysorb BLK was modified with saccharose in various coatings by weight and the influence of the degree of coating on the separation action of the carrier was studied. An appraisal was also made of the analytical application of such carriers.

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Résumé On a étudié la possibilité d'utiliser des corps solides de petites surfaces comme sorbants en Chromatographie en phase gazeuse. On a expérimenté les propriétés de sorption des supports sur base de kieselguhr, de Rysorb BLK, LM et P. Le Rysorb BLK a été modifié avec le saccharose avec un revêtement différent et équivalent et Ton a étudié l'influence du degré de revêtement sur l'action séparatrice du support. On a apprécié de plus l'emploi de ces supports en analyse.

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Herrn Prof. Dr. Ing.M. Jureek zum 60. Geburtstag gewidmet.     

Estimation of diuretic drugs in biological fluids by HPLC

Summary This critical review of different methods proposed for the determination and screening of diuretics is directed mainly, because of its potential application, towards highperformance liquid chromatography.     

Multiparametric curve fitting-I Computer-assisted evaluation of chelatometric titrations with metallochromic indicators

A curve-fitting procedure has been developed for the photometric complex-formation titration of the metal-indicator complex MIn(N) which is assumed to predominate in solution. By means of a least-squares procedure the following five parameters were determined: the end-point, the absorbance of the indicator complex A(M)XXX. the indicator concentration CXXX, the stability constants and, if possible, k(MY) . A modified version of Sillen's Letagrop Vrid has been used for the mathematical-statistical approach of the non-linear model based upon the non-transformed function A = f(v). Additional information is obtained about the goodness of fit, indicating whether the chosen model with predominance of MIn(N) is correct or not. The use of the program is demonstrated by application to chelatometric microtitrations of zinc and lead with EDTA, using Naphthylazoxine 6S and SNAZOXS as metallochromic indicators.     

Stereospecific total synthesis of (±)-strempeliopine

The 18-methylene-1,2-dehydroaspidospermidine (III) was stereospecifically transformed into the schizozygane alkaloid strempeliopine (II) in 16,6 % overall yield.     

Gas Phase Catalysis by Metal Nanoparticles in Nanoporous Alumina Membranes

Nanoporous alumina membranes, loaded with palladium and ruthenium nanoparticles of various size, were used for gas phase hydrogenation of 1, 3‐butadiene and for oxidation of carbon monoxide, respectively. Those membranes contain 10⁹ ‐ 10¹¹ pores per cm², all running perpendicular to the surface. Membrane discs of 20 mm in diameter and only 60 μm thick, incorporated in a reactor in which the reactants can be pumped in a closed circuit through the pores, turned out to very actively catalyze hydrogenation of butadiene (Pd) and oxidation of CO (Ru). The activity of the Pd catalysts depends characteristically on the particles size, the gas flow, and of the educts ratio. As could be expected, larger particles are less active than smaller ones, whereas increasing gas flows in case of hydrogenation accelerates the reactions. Excessive hydrogen reduces selectivity with respect to the various butenes, but favours formation of butane.     

Osmotic behavior of a Nafion membrane in methanol-water electrolyte solutions

In this paper, an experimental study was carried out in order to investigate the osmotic transport of methanol-water electrolyte solutions through a Nafion membrane. The experimental data indicated that the Nafion membrane showed the typical anomalous osmotic behavior of charged membranes. The influence of some relevant parameters, such as electrolyte concentration difference, weight fraction of methanol on solution, and nature of cation was considered. The results showed that the osmotic volume flow was decreased with the presence of methanol on solvent, but did not alter the anomalous osmotic behavior of the membrane.     

Rapid and simple method for determination of Nepsilon-(carboxymethyl)lysine and Nepsilon-(carboxyethyl)lysine in urine using gas chromatography/mass spectrometry

A new procedure was developed to determine in urine the concentrations of N(epsilon)-(carboxymethyl)lysine (CML) and N(epsilon)-(carboxyethyl)lysine (CEL), the major products of oxidative modification of glycated proteins, to assess levels of oxidative stress in physiological systems. The urine samples were acetonitrile-deproteinized, then derivatized by ethylchloroformate, and N(O,S)-ethoxycarbonyl ethyl esters of amino acids were analysed by isotope dilution gas chromatography/mass spectrometry. Recovery averaged 89%. Linearity was excellent (r = 0.998-0.999) in the 0.5-25 micromol/L range for CML and CEL. The limit of detection of this assay was 0.1 micromol/L (corresponding to 0.20 pmol of CML or CEL on column). Intra-day and inter-day precisions were likewise excellent, with relative standard deviations <4.63 and <6.15%, respectively. Accuracy of CML and CEL determination (15 micromol/L) was 2.9 and 5.9% of the estimated theoretical value. The time from obtaining the urine sample to determination of the concentration from the chromatographic peak was 80 min or less. This method is sensitive, reproducible, accurate, relatively cheap and very simple. It can be useful for laboratories involved in the diagnosis and monitoring of age-related chronic diseases.     

Utilization of zirconia stationary phase as a tool in drug control

Zirconia-based stationary phases represent an interesting alternative to silica-based materials. Two zirconia-based stationary phases were studied as an option for use in drug analysis. The different properties of zirconia material, distinct from RP silica-columns, were employed for the development of a novel and rapid stability monitoring HPLC method. This method enables simultaneous control of possible degradation processes of active substance (ibuprofen) as well as antimicrobial excipients (methyl-and propylparaben). The separation of ibuprofen, its two main degradation products 2-(4-isobutyrylphenyl)propionic acid and 4-isobutylacetophenone, parabens, and 4-hydroxybenzoic acid as their degradation product was successfully accomplished on a Zr-CarbonC18 column using a mobile phase consisting of acetonitrile-phosphate buffer (pH 4.8)-propan-2-ol (27:56:17, v/v/v). Detection was performed at 258 nm and the analysis was completed within 17 minutes.     

Indirect Determination of Captopril with Sodium Nitrate and Thiocyanate by Floatation Separation of Copper

A new method for indirect determination of captopril (CPT) with NaNO₃ and NH₄SCN by floatation and separation of copper has been studied. In the weak acid, a small amount of Cu(II) can be reduced to Cu(I) by CPT, then Cu(I) reacted with the SCN, which can float on the surface of the liquid phase with NaNO₃. A good linear relationship is observed between the floatation yield (E%) of Cu(II) and the amount of captopril. The linear range is 2?32 mg/L. On the ground, captopril can be indirectly determined by determining E(%) of Cu(II). The method is simple, rapid, reliable and has good selectivity. The developed method can be applied to indirect determination of captopril with satisfactory results.