A New Approach to Increasing the Resolution of a Mass Spectrometer with Wedge-Shaped Reflectors

The paper describes the investigation of the ion-optical properties of a laser TOF mass spectrometer including two successively positioned wedge-shaped ion mirrors. Some specific properties of the configuration of ion trajectories near their reflection in the second ion reflector are found. The dependence of aberrations on ion energy acquired toothed shape for the resolution of the analyzer higher than 3000–5000. The approximation of the dependence gave a 15^th degree polynomial. The calculation of polynomial coefficients showed a great contribution to the duration of ion packets for aberrations of higher order. The discovered features allowed us to suggest a way of the local correction of nearby trajectories in the total ion flux. By correcting the local motion of individual groups of ions, we could reduce temporary aberration to 1–1.6 ns, depending on ion energy. For the time of ion flight ~35 μs, such duration limits the resolution of the analyzer by a value not less than 10000. The real length of ion drift path was about 30 cm. The total overall sizes of the ionoptical system were ~24 × 19 × 5 cm.     

Solution state and complexing ability of 1,4-bis(amidomethylsulfinyl)butane toward iron(III), copper(II), cobalt(II), nickel(II), and manganese(II)

The solution state and thermodynamic stability of complexes of the new antituberculosis agent 1,4-bis(amidomethylsulfinyl)butane (L) with iron(III), copper(II), cobalt(II), nickel(II), and manganese(II) in an aqueous solution in the presence and in the absence of the nonionic surfactant Brij 35 were studied by spectrophotometry, pH potentiometry, NMR relaxation technique (T = 25 °C; variable ionic strength), and mathematical simulation. The geometry optimization of all structures was carried out by the molecular mechanics method MM2 in order to obtain data on coordination modes. In addition, the structure of 1,4-bis(amidomethylsulfinyl)butane was refined by the DFT/B3LYP/6-311++G(d,p) quantum chemical method using the IEFPCM model to take into account solvent effects. In an aqueous solution (in the concentration range of 1.3?10^–5—1?10^–3 mol L–1) and in the presence of Brij 35, 1,4-bis(amidomethylsulfinyl)butane exists as a neutral monomer. The Beer—Lambert—Bouguer law is obeyed in a wide concentration range for compound L in an aqueous solution, as well as in the presence of the surfactant, which can be used for the quantification of compound L. Iron(III), cobalt(II), and nickel(II) were shown to form 1: 1 mononuclear complexes with L; and copper(II) forms, 1: 1 and 2: 2 complexes. The presence of Brij 35 in the Cu²⁺—L system at a micellar concentration promotes the formation of a dinuclear complex.     

Alkylation of phenol with olefins in the presence of catalysts based on mesoporous aromatic frameworks

Mesoporous polyaromatic frameworks (PAFs) based on tetraphenylmethane were obtained and modified with sulfonic acid groups. The compounds were characterized by solid-state ¹³C NMR and IR spectroscopy, low-temperature nitrogen adsorption-desorption, and transmission electron microscopy. The acidities of the PAF-1-SO₃H and PAF-2-SO₃H samples determined by titration were 3.99 mmol g^–1 and 0.91 mmol g^–1, respectively. The catalytic activity of PAF-SO₃H for alkylation of phenol with linear terminal olefins was investigated. The reaction products were isomeric monoalkylphenols (C-alkylates), and alkyl phenyl ethers (O-alkylates).     

Conjugation of indole derivatives by copper-catalyzed alkyne-azide cycloaddition

An efficient synthetic procedure to combine biologically active indole derivatives by the triazole-containing spacer in a molecule has been proposed. The procedure was based on a copper-catalyzed alkyne-azide cycloaddition of azide-containing carbazoles and N-propargyl-containing carbazoles, tetrahydrocarbazoles, and tetrahydro-γ-carbolines.     

Heterocyclization of carboxy- and sulfonamides in the course of oxidative addition to unsaturated substrates

Formation of heterocyclic compounds in the course of oxidative addition of carboxamides and sulfonamides to alkenes and dienes is reviewed. Main attention is focused on reactions proceeding in the presence of halo-containing oxidative systems and reagents. Features of behavior of fluorine-substituted sulfonamides and carboxamides are discussed.     

Preconcentration and separation of <Superscript>99</Superscript>Tc in groundwater by using TEVA resin

An effort has been made to optimize the counting time for low-level measurement of naturally occurring radioactive material (NORM) by considering the standard deviation between the activity values of different photopeaks and counting error. It is observed that at lower counting time, relative standard deviation (RSD) varies randomly, but attains a gradual trend with increasing time and also comes closure to the counting error. Therefore minimum counting time for low-level NORM measurement of ²³⁸U and ²³²Th would be the time required to stabilize the RSD values.     

Polyethylenimine and tris(2-aminoethyl)amine modified p(GA–EGMA) microbeads for sorption of uranium ions: equilibrium,kinetic and thermodynamic studies

Poly(glycidyl methacrylate-ethyleneglycol dimethacrylate), p(GA–EGMA), microbeads were prepared through suspension polymerization. It was decorated with polyethylene imine (PEIM) and tris(2-aminoethyl)amine (TAEA) ligands to decorate with polyamine groups. These microbeads were used for sorption of uranium ions from aqueous solution. The maximum sorption of uranium ions on the PEIM and TAEA modified microbeads was observed at pH 6.0. The maximum sorption capacity of acid hydrolyzed p(GA–EGMA)–OH, p(GA–EGMA)–PEIM and p(GA–EGMA)–TAEA microbeads was found to be 7.21, 87.8 and 64.3 mg g^?1. The sorption process conforms to the pseudo-second order kinetic model and the Langmuir and Temkin isotherm models well.     

Measurement of <Superscript>3</Superscript>H,gross <Emphasis Type="Italic">α/β</Emphasis> and <Superscript>222</Superscript>Rn in drinking water using the new Quantulus GCT 6220

Since the introduction of the European Council Directive 2013/51 Euratom in October 2013, the analysis of drinking water has increasingly become the focus of many laboratories in Europe. The activity of tritium, radon and the gross α/β-activity is determined routinely. In order to cope with the increased sample numbers and to reach the necessary detection limits, sensitive measuring devices are required. This work was done with the new Quantulus GCT 6220 to test the sensitivity of this system for drinking water analysis. The results indicate that this instrument is very well suited for this type of analysis and counting times are typically below the required counting times of established systems.     

Structural requirement of C11b chirality of tetrabenazine analogs as VMAT2 imaging ligands: synthesis and in vivo evaluation

We studied on the structural requirement of C11b chirality of tetrabenazine (TBZ) analogs as vesicular monoamine transporter 2 (VMAT2) ligands. TBZ analogs (2, 6a, 6b) and ¹⁸F-radiolabeled [¹⁸F]6a and [¹⁸F]6b with eliminated C11b chirality were synthesized and characterized. Competition studies demonstrated that 2, 6a and 6b displayed much lower in vivo VMAT2 bindings than TBZ. MicroPET imaging studies of [¹⁸F]6a and [¹⁸F]6b showed negligible accumulation in VMAT2-enriched regions as compared with the known VMAT2 ligand ¹⁸F-FP-(+)-DTBZ. These results suggest that C11b chirality of TBZ analogs is essential for in vivo VMAT2 binding bioactivity.     

Detection efficiency calculations using Geant4 for a broad-energy germanium gamma spectrometer

In assistance of radionuclide measurements at Canada’s Comprehensive Nuclear-Test-Ban Treaty (CTBT) laboratory, a Geant4 Monte Carlo application has been developed in simulating a broad-energy germanium detector and calculating detection efficiencies. The detector model was optimized in a reliable and non-biased manner through simultaneous tuning on gap distance and detector dimension, and was validated over various realistic measurement scenarios. All work is based on a series of experiments which covers the typical energy range of gamma radiation in environmental analysis, and considers the variety of the CTBT sample type, dimension and distance-to-detector. In all cases, the predicted efficiencies are consistent with the empirical ones within 5%, with a typical deviation of 3% in majority.