Esterification of C1−C8 carboxylic acids to n-butyl esters in aqueous solutions for their gas chromatographic analysis

Summary The esterification of C₁–C₈ fatty acid in aqueous solutions and in the presence of sulfuric or hydrochloric acid and with n-butanol is described. It has been established that the esterification can be used for the quantitative determination of these fatty acids in the concentration ratio range of [H₂O]/[n-BuOH]=0.01–5.3. In the concentration ratio range of 0.01–0.8 the water present does not interfere. In the concentration range of above 0.8 anhydrous sodium sulfate is used for binding the water, in the amount of [Na₂SO₄.anh.]/[H₂O]0.2.     

Quantitation of amino acids in plasma by high performance liquid chromatography: Simultaneous deproteinization and derivatization with 9-fluorenylmethyloxycarbonyl chloride

This paper, as a novelty to this field, presents the deproteinization and derivatization of plasma's free amino acids (PFAAs), simultaneously, in a single step, with the acetonitrile (ACN) containing 9-fluorenylmethyloxycarbonyl chloride (FMOC) reagent. Deproteinization and derivatization, were studied with 22 amino acids, applying photodiode array (DAD) and fluorescence (FL) detection, simultaneously. Model investigations have been carried out as a function of the FMOC concentration, reaction time and reaction conditions: with standard solutions, with human plasma samples in its initial condition and fortified with standard amino acids (excluding tryptophan because it co-elutes with the hydrolyzed FMOC). Reproducibilities of 22 amino acids, including both histidine and tyrosine derivatives, obtained under optimum derivatization conditions are presented (at 3.0 mM FMOC concentration, at pH 9; derivatization time = 20 min), and characterized with the relative standard deviation percentages of their responses (≤4.4%, RSD). Quantitation limit (LOQ) of amino acid FMOC derivatives proved to be 2.5 pmol, except for cystine, ornithine (5 pmol) and for the total of tyrosines (N-FMOC-tyrosine and N,O-FMOC-tyrosine 10 pmol).     

Identification and quantification of the constituents of madder root by gas chromatography and high-performance liquid chromatography

The possibilities in the identification and quantitation of the constituents of Rubia tinctorum L.'s root, called also madder root, was described and compared by gas chromatography (GC)-MS, high-performance liquid chromatography (HPLC)-UV/photodiode array detection (DAD) and HPLC-MS: chromatographic analyses were carried out in parallel, from the same samples/extracts/hydrolyzates. Anthraquinone glycosides, anthraquinones, carboxylic acids and sugars were determined directly in the presence of the matrix and in its extracts without and subsequently to hydrolyses. Hydrolyses were performed as a function of time, with hydrochloric and trifluoroacetic acids, as well as enzymatically. Data revealed that as hydrolyzing agent trifluoroacetic acid is to be preferred. Madder root's anthraquinones (pseudopurpurin/purpurin, alizarin, lucidin, munjistin, nordamnacanthal) were identified on the basis of their absorption spectra (HPLC-DAD) and fragmentation patterns by GC-MS and HPLC-MS, equally. Reproducibility of anthraquinone's quantitation, by HPLC-DAD and GC-MS, in the concentration ranges of 4 x 10(-5) to 3 x 10(-2)g/g dried sample, provided an average reproducibility of 4.2% (varying between 0.9 and 9.4% relative standard deviation (RSD percentages)). Carboxylic acids (malic, citric, quinic, rosmarinic acids) and saccharides (xylose, ribose, fructose, glucose, sucrose, primverose) were quantified as their trimethylsilyl (oxime) ether/ester derivatives by GC-MS, in the concentration ranges of 10(-5)g to 10(-2)g/g dried sample, with an average reproducibility of 4.7% RSD.     

Synergetic effect of host-guest chemistry and spin crossover in 3D Hofmann-like metal-organic frameworks [Fe(bpac)M(CN)4] (M=Pt, Pd, Ni)

The synthesis and characterization of a series of three‐dimensional (3D) Hofmann‐like clathrate porous metal–organic framework (MOF) materials [Fe(bpac)M(CN)₄] (M=Pt, Pd, and Ni; bpac=bis(4‐pyridyl)acetylene) that exhibit spin‐crossover behavior is reported. The rigid bpac ligand is longer than the previously used azopyridine and pyrazine and has been selected with the aim to improve both the spin‐crossover properties and the porosity of the corresponding porous coordination polymers (PCPs). The 3D network is composed of successive {Fe[M(CN)₄]}_n planar layers bridged by the bis‐monodentate bpac ligand linked in the apical positions of the iron center. The large void between the layers, which represents 41.7 % of the unit cell, can accommodate solvent molecules or free bpac ligand. Different synthetic strategies were used to obtain a range of spin‐crossover behaviors with hysteresis loops around room temperature; the samples were characterized by magnetic susceptibility, calorimetric, Mössbauer, and Raman measurements. The complete physical study reveals a clear relationship between the quantity of included bpac molecules and the completeness of the spin transition, thereby underlining the key role of the π–π stacking interactions operating between the host and guest bpac molecules within the network. Although the inclusion of the bpac molecules tends to increase the amount of active iron centers, no variation of the transition temperature was measured. We have also investigated the ability of the network to accommodate the inclusion of molecules other than water and bpac and studied the synergy between the host–guest interaction and the spin‐crossover behavior. In fact, the clathration of various aromatic molecules revealed specific modifications of the transition temperature. Finally, the transition temperature and the completeness of the transition are related to the nature of the metal associated with the iron center (Ni, Pt, or Pd) and also to the nature and the amount of guest molecules in the lattice.     

Classification of Sol lattices

Sol geometry is one of the eight homogeneous Thurston 3-geometries $${\bf E}^{3}, {\bf S}^{3}, {\bf H}^{3}, {\bf S}^{2}\times{\bf R}, {\bf H}^{2}\times{\bf R}, \widetilde{{\bf SL}_{2}{\bf R}}, {\bf Nil}, {\bf Sol}.$$ In [13] the densest lattice-like translation ball packings to a type (type I/1 in this paper) of Sol lattices has been determined. Some basic concept of Sol were defined by Scott in [10], in general. In our present work we shall classify Sol lattices in an algorithmic way into 17 (seventeen) types, in analogy of the 14 Bravais types of the Euclidean 3-lattices, but infinitely many Sol affine equivalence classes, in each type. Then the discrete isometry groups of compact fundamental domain (crystallographic groups) can also be classified into infinitely many classes but finitely many types, left to other publication. To this we shall study relations between Sol lattices and lattices of the pseudoeuclidean (or here rather called Minkowskian) plane [1]. Moreover, we introduce the notion of Sol parallelepiped to every lattice type. From our new results we emphasize Theorems 3?C6. In this paper we shall use the affine model of Sol space through affine-projective homogeneous coordinates [6] which gives a unified way of investigating and visualizing homogeneous spaces, in general.     

Nondestructive Analysis of Metals by PGAA at the Budapest Research Reactor

Since 1996 several applications of prompt gamma activation analysis have been performed at the new Budapest PGAA facility. This paper deals with the investigation of metal objects. We report the results of nondestructive detection of H in amorphous metals, multielement analysis of Roman bronze brooches and measurement of silver concentration in Hungarian coins.     

Nuclear Data for Activation Analysis

Nuclear data for neutron activation analysis are reviewed critically. Available sources of neutron cross sections and related quantities, radioactive decay half-lives, gamma-ray energies and absolute intensities, as well as prompt gamma-ray data are assessed from the viewpoint of quantitative analysis. New developments in the production and dissemination of such data are also described, and practical recommendations are formulated. Special emphasis is given to the traceability of sources, the accuracy and age of data, and to electronic access via Internet.     

Cyclodextrins in innovative engineering tools for risk-based environmental management

Experimental results, which may serve as basis for innovative applications of cyclodextrins (CDs) in environmental technologies, are presented here. Some newly developed CD-aided tools are used in sampling, measuring the concentration or testing the effect of contaminants in water and soil. The innovative methods such as the bacterial bioassays with CD-increased sensitivity or the CD-filled absorptive samplers for air and water sampling are utilised in environmental exposure, hazard and risk assessment. Technological developments aim the reduction of the risk of chemical substances in waters and soils. CD-aided environmental remediation is introduced through examples for the elimination of organic contaminants from water by CD-filters, and for the enhancement of the mobility and availability of soil contaminants in this way increasing the efficiency of soil remediation by water extraction, chemical oxidation, biodegradation, etc.