Non-aqueous capillary zone electrophoresis method for the analysis of paroxetine, tamoxifen, and their main metabolites in urine

The potential of non-aqueous capillary electrophoresis (NACE) was investigated for the simultaneous separation of paroxetine, tamoxifen, and their main metabolites. Baseline separation of the studied solutes was obtained on a  μm capillary using a non-aqueous buffer composed of 18 mM ammonium acetate and 1.1% acetic acid in 80:20 (v/v) methanol-acetonitrile, with a temperature and voltage of 22 °C and 15 kV, respectively. Clomipramine was used as internal standard. Aspects such as stability of the solutions, linearity, accuracy, precision and ruggedness were examined in order to validate the proposed method. Detection limits obtained for all the studied compounds ranged between 3.0 and 7.1 μg l⁻¹. The developed method is sensitive and robust and was used to determine paroxetine, tamoxifen, and their metabolites at clinically relevant levels in human urine. Before NACE determination, the samples were purified and enriched by means of an extraction-pre-concentration step with a pre-conditioned C₁₈ cartridge. Determination of these analytes in the urine of four females urines was demonstrated.     

The six-membered annulation reaction involving sequential palladium-catalyzed allylic alkylation and Michael addition: scope and limitations

The palladium-catalyzed condensation of a variety of active methylene compounds with methyl 6-acetoxymethyl-hepta-2,6-dienoate was investigated. The six-membered adducts resulting from a η³ palladium complex alkylation-Michael addition sequence were obtained with moderate to good yields. In some cases, further evolution of the primary adduct was observed. The process has been expanded to access nitrogen heterocycles by using sodium p-toluenesulfonamide as the nucleophilic partner.     

Preparative Separation and Analysis of Complex Mixtures of Leucomycins and Desmycarosyl Leucomycins Using HPLC and Mass Spectrometry

Composition and hydrolysis products of a biotechnical available complex of macrolides were analyzed by HPLC and ESI-CID-MSⁿ. Major components are leucomycin-type antibiotics (leucomycins A₁ (5), A₇ (3), A₉ (2), 9-desoxy-9-oxo-turimycin H₃ (4) and niddamycin B (6). Hydrolysis of the complex mixture yielded 9-, 13-isoforocidins (7, 8, 9, 11) and 9-oxo-forocidin (10). A preparative separation procedure was elaborated furnishing compounds 3 - 11 for semisynthetic experiments.Prof. Dr. Udo Gräfe deceased on 14.2.2003. For obituarity see: Schlegel B (2003) J Peptide Sci 9: 661–661.     

Chemo- and regioselectivity in the reactions between highly electrophilic fluorine containing dicarbonyl compounds and amines. Improved synthesis of the corresponding imines/enamines

Chemo- and regioselectivity in the reactions between highly electrophilic fluorine containing dicarbonyl compounds (ethyl 4,4,4-trifluoroacetoacetate, 3,3,3-trifluoropyruvate and 1,1,1,5,5,5-hexafluoropentane-2,4-dione) and various benzylamines were systematically studied. The results obtained lead to the development of a generalized and practical method for large-scale synthesis of the corresponding imines/enamines, useful starting materials for preparation fluorinated amines and amino acid.     

Glucomannan from Narcissus poeticus Studied by PMR and 13C NMR Spectroscopy

Native acetylated glucomannan of molecular weight (MW) 32000 with a glucose:mannose ratio 1:30 was isolated from bulbs of Narcissus poeticus. Glucomannan was depolymerized to a fragment of MW 15000 with an unchanged primary structure and was studied using PMR and ¹³C NMR spectroscopy. It was found that the linear chain of the biopolymer consists of 1-4-bound D-gluco- and D-mannopyranose units and the O-Ac groups are localized on C-2, C-3, and C-6 hydroxyls in certain anhydromannose units.     

The identification of nitrated polycyclic aromatic hydrocarbons in diesel particulate extracts and their potential formation as artifacts during particulate collection

Summary The highly complex matrix of diesel particulate extracts was analyzed for nitrated polycyclic aromatic hydrocarbons (nitro-PAH) using fused-silica capillary-column gas chromatography along with a thermionic nitrogen-phosphorus detector (TID) and high-performance liquid chromatography followed by on-line catalytic reduction of the nitro-PAH to amino-PAH and subsequent fluorescence detection. Positive isomer identification and quantitation of nitro-PAH are from retention times of authentic standards and their mass spectra. The ease of nitro-PAH formation by nitration of PAH raises the question regarding the origin of these species, whether they are produced as “native” products during the engine combustion process and/or in the exhaust, or instead, formed as the result of chemical conversion to produce artifacts during the sampling procedure. This problem is assessed examing 1-nitropyrene-concentration in particulates of three light-duty diesel engines for different sampling times. 1-Nitropyrene concentrations show only a moderate increase with sampling time under average sampling conditions. Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984     

Determination of d-glucose in undiluted whole blood using chemically modified electrodes and segmented sample injection in a flow system

A flow system for the determination of d-glucose in undiluted whole blood, in which segmented sample injection and on-line dialysis are used to decrease the red cell volume fraction (haematrocrit) dependence, is described. Glucose is degraded enzymatically by means of immobilized glucose dehydrogenase. The nicotinamide coenzyme (NAD⁺) that is present in the solution is reduced in the enzymatic reaction and is reoxidized amperometically at 0 mV vs. Ag/AgCl on a graphite electrode, modified with phenoxazinium ion. The potential use of the system for clinical analysis is evaluated.     

Viscosity of mixtures of polymers and microemulsions — the Huggins interaction coefficient

Microemulsions used in enhanced oil recovery are usually used in conjunction with a polymer solution that provides mobility control by reducing the permeability of the formation and/or increasing the viscosity of the injected fluid. Microemulsions, which are mixtures of at least four components — water, oil, surfactant and cosurfactant (and, usually, inorganic salts) are complex even in the absence of polymer and consequently, studies of their phenomenon tend to be phenomenological. An approach found to be useful to circumvent this has been to consider the microemulsion particles dispersed in their external phase to be macromolecules which retain their integrity when diluted with external phase or when mixed with polymers. Thus the dispersed phase components are treated as a pseudocomponent. If this approach is followed, many features of the phase diagram of polymer-microemulsion mixtures can be rationalized. It is therefore of some interest to determine whether a similar approach can be used to understand or predict the viscosity of mixtures in which a simple mixing rule for viscosities can be utilized to gain further insight into the polymer-microemulsion interaction.     

Enantioselectivity of 6-O-alkyldimethylsilyl-2,3-di-O-methyl-β-cyclodextrins as chiral stationary phases in capillary GC

Summary Clenbuterol has been determined in urine by solidphase extraction on a C₁₈ cartridge, diazotization of the eluate with nitrite, coupling of the diazonium ion with 1-(naphthyl)ethylenediamine, and separation of the azo dye formed by HPLC with a C₁₈ column and a micellar mobile phase containing 0.1 M sodium dodecyl sulphate, 12%n-butanol and 0.05 M citrate buffer, pH 3. Recoveries higher than 90% were obtained by mixing the samples with a 20% 0.2 M NaOH before extraction. Limits of detection of 51 and 6.7 ng L⁻¹ were obtained with spectrophotometric and thermal lens spectrometric detection, respectively; respective repeatabilities were 3.1% (5 μg mL⁻¹) and 5.6% (0.16 μg mL⁻¹).     

Studies of surface properties of Na- and La-montmorillonites

This paper presents possible applications of thermal analysis, sorptometry and porosimetry to study physico-chemical properties of Na- and La-montmorillonite samples, especially for determination of total surface heterogeneity. The quasi-isothermal thermogravimetric (Q-TG) mass loss and its first derivative (Q-DTG) curves with respect to temperature and time obtained during programmed liquid thermodesorption under quasi-isothermal conditions have been used to study adsorbed layers and heterogeneous properties of the Na- and La-montmorillonites. Calculations of the desorption energy distribution functions by analytical procedure using mass loss Q-TG and differential mass loss Q-DTG curves of thermodesorption under quasi-isothermal conditions of polar and non-polar liquid vapours preadsorbed on a material surface are presented. Parameters relating to porosity of samples were determined by sorptometry, mercury porosimetry and atomic force microscopy (AFM). From nitrogen sorption isotherms from sorptometry and porosimetry methods, the fractal dimensions of montmorillonites have been calculated. Moreover, a new approach is proposed to calculate fractal dimensions of materials obtained from Q-TG curve; this is compared with values obtained by the above methods. The total heterogeneous properties (energy distribution function and pore-size distribution functions) of samples studied were estimated. The radius and pore volume of the tested samples calculated on the basis of thermogravimetry, sorptometry and porosimetry techniques were compared and good correlations obtained.