Excess Molar Volumes and Liquid–Liquid Equilibria of the Ionic Liquid 1-Methyl-3Octyl-Imidazolium Tetrafluoroborate Mixed with Butan-1-ol and Pentan-1-ol

Experimental densities were measured for the system 1-methyl-3-octyl-imidazolium tetrafluoroborate [OMIM][BF₄] + butan-1-ol, + pentan-1-ol at 298.15 K and ambient pressure using a vibrating tube densimeter, taking into account the influence of the viscosity correction. Excess molar volumes V^E have been determined. V^E is quite small and negative in the alcohol-rich range of the mixture composition and positive in the alcohol-poor range. LLE data of [OMIM][BF₄] + pentan-1-ol have been measured using a laser light scattering cell for detecting cloud points at different compositions in the temperature range of 282–292 K. A miscibility gap with an upper critical solution temperature (UCST) of 292 K has been found.     

Synthesis and characterization of new strontium 4-carboxyphenylphosphonates

Several new strontium 4-carboxyphenylphosphonates, i.e., two modifications of Sr(HOOCC₆H₄PO₃H)₂, SrH(OOCC₆H₄PO₃)·H₂O, Sr₃(OOCC₆H₄PO₃)₂·4H₂O and Sr₃(OOCC₆H₄PO₃)₂·5.7H₂O were prepared and characterized by elemental analysis, thermogravimetry, X-ray powder diffraction and infrared spectroscopy. It was found that the compositions of these compounds depend on the acidity of the reaction medium. In addition, the presented compounds are interconvertible in dependence on pH. The position of the acid hydrogen atom in SrH(OOCC₆H₄PO₃)·H₂O was determined from the IR spectra of the studied compounds.The structure of the β modification of Sr(HOOCC₆H₄PO₃H)₂ was solved from its X-ray powder diffraction pattern using an ab initio method (the FOX program) with subsequent Rietveld refinement in the FULLPROF program. The compound is monoclinic, with the space group P2₁/c (No. 14), a=49.88(2), b=7.867(2), c=5.602(3) Å, β=128.68(2)°, and Z=4. It has a one-dimensional structure with an inorganic part built of SrO₈ distorted tetragonal antiprisms.     

A simple and fast micromethod for the analysis of polychlorinated biphenyls in air by sorbent enrichment and ultrasound-assisted solvent extraction

A combination of sorbent enrichment and ultrasound-assisted solvent extraction has been used to determine polychlorinated biphenyls in air. Analytes were sampled by pumping a known volume of air through a porous polymer (Tenax TA). The enriched adsorbent was transferred into a glass vial, and ultrasound-assisted extraction of the analytes was then performed in n-hexane. Quantification was carried out by using gas chromatography coupled to tandem mass spectrometry. Breakthrough volume of the sampling step was studied, indicating that 10 m³ of air could be processed without losses of the most volatile compounds. Good recoveries (75–96%) were obtained, and limits of detection at the sub ng m^–3 were achieved for all the analytes. The proposed method is very simple and fast, avoiding the use of large solvent volumes and time-consuming preconcentration steps.     

Stereoselective synthesis of (R)-(+)-1-methoxyspirobrassinin, (2R,3R)-(−)-1-methoxyspirobrassinol methyl ether and their enantiomers or diastereoisomers

Stereoselective synthesis of cruciferous indole phytoalexin (R)-(+)-1-methoxyspirobrassinin and its unnatural (S)-(−)-enantiomer was achieved by spirocyclization of 1-methoxybrassinin in the presence of (+)- and (−)-menthol and subsequent oxidation of the obtained menthyl ethers. Methanolysis of menthyl ethers in the presence of TFA afforded (2R,3R)-(−)-1-methoxyspirobrassinol methyl ether as well its unnatural (2S,3S)-, (2R,3S)-, and (2S,3R)-isomers.     

Analysis of dinitro- and amino-nitro-toluenesulfonic acids in groundwater by solid-phase extraction and liquid chromatography–mass spectrometry

A reversed-phase LC–MS method with quadrupole-time of flight (QTOF) detection has been developed for the determination of four dinitro-toluenesulfonic acids and two amino-nitro-toluenesulfonic acids in groundwater. The analytes were separated by HPLC with 0.1% (v/v) formic acid as mobile phase modifier compatible with mass spectrometric detection. QTOF-MS analysis with negative ion electrospray ionization afforded good selectivity and sensitivity for analysis of the dinitro- and amino-nitro-toluenesulfonic acids. Structure elucidation and confirmation were accomplished by tandem mass spectrometry. Characteristic ions resulting from the loss of NO, NO₂, and SO₂ from the [M–H]^– ions were detected. An intense fragment ion at m/z 80 representing the [SO₃]^– ion was detected for all dinitro- and amino-nitro-toluenesulfonic acids. Solid-phase extraction using a co-polymer cartridge was developed for preconcentration of the analytes from water. Good recovery (>85%) was achieved when 0.1% formic acid was added into the water samples before extraction. Method detection limits ranged from 10 to 76 ng L^–1 for the targeted compounds when 10 mL water was analyzed. Groundwater samples collected from wells close to a former ammunition plant in Stadtallendorf, Germany, were analyzed for the dinitro- and amino-nitro-toluenesulfonic acids.     

Estimation of binding constants between ristocetin and teicoplanin and peptides using on-column ligand derivatization coupled to affinity capillary electrophoresis

This work utilizes on-column ligand synthesis and affinity capillary electrophoresis (ACE) to determine binding constants (K_b) of 9-flourenylmethyloxy carbonyl (Fmoc)-amino acid derivatives to the glycopeptide antibiotics ristocetin (Rist) and teicoplanin (Teic). In this technique, two separate plugs of sample are injected on to the capillary column and electrophoresed. The initial sample plug contains a d-Ala-d-Ala terminus peptide and either one or two non-interacting standard(s). The second plug contains a Fmoc-amino acid-N-hydroxysuccinimide (NHS) ester. The electrophoresis is then carried out with an increasing concentration of Rist or Teic in the running buffer. Upon electrophoresis the initial d-Ala-d-Ala peptide reacts with the Fmoc-amino acid yielding a new Fmoc-amino acid-d-Ala-d-Ala peptide derivative. Continued electrophoresis results in the binding of Rist or Teic to the Fmoc-amino acid-d-Ala-d-Ala peptide derivatives. Analysis of the change in the relative migration time ratio (RMTR) or electrophoretic mobility () of the Fmoc-amino acid-d-Ala-d-Ala peptide derivatives relative to the non-interacting standards, as a function of the concentration of Rist and Teic, yields a value for K_b. These findings demonstrate the advantage of coupling on-column ligand synthesis to ACE for estimating binding parameters between antibiotics and ligands.Abbreviations Rist Ristocetin - Teic Teicoplanin - ACE Affinity capillary electrophoresis - RMTR Relative migration time ratio     

Determination of the complex formation constants for some water-soluble polymers with trivalent metal ions by differential pulse polarography

The formation of metal complexes between water-soluble polymers, poly(vinyl alcohol) [PVA], poly(N-vinylpyrrolidone) [PVP], poly(acrylamide) [PAAm] and poly(ethylene oxide) [PEO] with trivalent metal ions, Fe³⁺, Cr³⁺, and V³⁺ were studied by using differential pulse polarography (DPP). The general experimental observation is the shift of totally reversible reduction peaks (M³⁺+Hg+e^–M²⁺+Hg) towards more negative potentials when the complexing water-soluble polymers are added to the solution of trivalent metal ions. The negative shift in potential permitted the determination of complex formation constants (K_f) between trivalent metal ions and water soluble polymers. The complex formation constants for Fe³⁺, Cr³⁺, and V³⁺ ions with these polymers increased in the order of V³⁺>Cr³⁺>Fe³⁺.     

Freon (CHF<Subscript>3</Subscript>)-assisted atomization for the determination of titanium using ultrasonic slurry sampling–graphite furnace atomic absorption spectrometry (USS–GFAAS): a simple and advantageous method for solid samples

A simple and advantageous method for the determination of titanium using graphite furnace atomic absorption spectrometry with slurry sampling has been developed. Titanium is one of the refractory elements that form thermally stable carbides in the graphite tube, which leads to severe memory effects. Trifluoromethane (Freon-23) was applied in the purge gas during the atomization step or alternatively just prior to the atomization to successfully eliminate the problems of carbide formation and increase the lifetime of the furnace tube which could be used for more than 600 heating cycles. A flow rate of 40 mL min^–1 (5% of Freon in argon) was used to obtain symmetrical peaks with no tailing. However, when the gas flow rate was too high (250 mL min^–1) the peak-tailing and memory effects reappeared. Ti was determined in various materials covering a wide range of concentrations, from 2.8 g g^–1 to 12% (m/m) Ti. The accuracy of the method was confirmed by analyzing certified reference materials (CRMs) or by comparing the results with those obtained using inductively coupled plasma–atomic emission spectrometry (ICP–AES) after decomposition of the samples. The materials analyzed were soil, plant, human hair, coal, urban particulate matters, toothpaste, and powdered paint.     

Planar and tubular perovskite-type membrane reactors for the partial oxidation of methane to syngas

Dense planar and tubular oxygen separation membranes of La_0.6Ca_0.4Fe_0.75Co_0.25O_3– were investigated as reactors for the partial oxidation (POX) of methane to syngas. Their permeation properties were measured in an air/argon pO₂ gradient as a function of temperature. At 900 °C, the oxygen flux through a 1.26-mm-thick membrane was 0.075 mol/cm²·s and through a 0.25-mm-thick tube, 0.24 mol/cm²·s.For the POX measurements, a catalyst was added to the membrane and methane was introduced on the argon side. This resulted in a gradual increase of the oxygen flux with increasing concentration of methane, reaching 2 mol/cm²·s at 900 °C with pure methane. For the planar reactor, the CO selectivity reached 99% and the CH₄ conversion 75% at 918 °C with pure methane. For the tubular reactor, the CO selectivity and CH₄ conversion were 83 and 99%, respectively, under the same conditions. After 1,400 h of operation in a tubular POX reactor, the membrane was examined revealing phase demixing and local decomposition.Presented at the OSSEP Workshop Ionic and Mixed Conductors: Methods and Processes, Aveiro, Portugal, 10–12 April 2003     

Analysis of Toxic Aluminium Species in Natural Waters

Aluminium is known to be toxic to a wide range of aquatic organisms under certain conditions. Monomeric hydroxy ions have been found to be primarily responsible for aluminium aquatic toxicity.A survey of aluminium toxicity and a brief discussion of speciation schemes are presented. The fast reaction of Al³⁺ with pyrocatechol violet (PCV) followed by spectrophotometric analysis is a frequently used method for aluminium speciation. By using a flow system, one obtains fairly exact and reproducible control of the reaction time, and as a result it provides a direct method of analysis for free aluminium (including inorganic monomeric aluminium).The PCV-method has been adapted for the determination of aluminium in carbonate-rich natural waters using an improved buffering system. Thus it is possible to monitor aluminium concentrations in lake water as well as in pore water of the sediments of eutrophicated hardwater lakes that has been treated with aluminium salts as a restoration measure.