Analytical performance of a high-pressure radio frequency-only quadrupole collision cell with an axial field applied by using conical rods

The effect on triple-quadrupole performance of applying an axial field, in an rf-only quadrupole collision cell operated at pressures sufficiently high that collisional focusing is operating, has been investigated. The advantages of such cells have been shown previously to include increased transmission and much improved resolution in fragment ion spectra relative to the performance of collision cells operating at lower gas pressures. The disadvantages of high-pressure collision cells all derive from the relatively long transit times for the ions, which can be long relative to characteristic times for scanning the first mass filter (precursor ion selector) or for switching its setting in multiple reaction monitoring (MRM) cycles. The present work describes experiments on a high-pressure cell in which an axial field is created through use of conical rather than cylindrical or hyperbolic rods. In addition, results of computations of the electric fields within such a cell, and of ion trajectories through it, are presented. It is shown that application of axial fields of the order of 0. 1 V/cm can remove all hysteresis effects associated with the long ion transit times, and thus provide excellent performance in quantitation work using MRM, as well as in other scan modes. Furthermore, the advantages of collisional focusing in quadrupole collision cells are shown to be unimpaired by these low axial fields.     

Synthesis and characterization of new polynuclear bis-5-oxy-1H-tetrazoles

Different bis-phenols reacted with cyanogen bromide in the presence of triethylamine as base to give the corresponding bis-cyanates which were treated with sodium azide in acetone as solvent to produce new bis(5-oxy-1H-tetrazole) derivatives. One more bis-tetrazole derivative was synthesized by reaction of 5-(4-aminophenoxy)-1H-tetrazole with adipoyl chloride. The prepared compounds were characterized by usual spectroscopic techniques. Published in Russian in Zhurnal Organicheskoi Khimii, 2009, Vol. 45, No. 1, pp. 156–159. The text was submitted by the authors in English.     

Preparation of a fast-flow agarose-based chelating adsorbent with a novel dioxime derivative for selective column preconcentration of copper.

Fast-flow spherical homogeneous agarose beads were prepared by an emulsification method, and were cross-linked and activated by repeated treatment with allylbromide and bromine/water, followed by alkali. Bis(2-aminopyridyl)dioxime (APD) was synthesized by the reaction of 2-aminopyridine, and dichloroglyoxime and characterized by melting-point as well as IR, 1HNMR, 13CNMR and MS spectroscopies. APD was chemically linked to activated agarose beads to be employed for the column preconcentration of metal ions. Capacity measurements for eight metal ions indicated a high selectivity of the adsorbent towards Cu2+ with a capacity of 25.7 micromol per ml packed adsorbent. A factorial design was used for optimization of the effects of 5 different variables on the recovery of Cu2+. Under the optimized conditions, Cu2+ was quantitatively accumulated on a 0.25 ml packed column of the adsorbent in the pH range of 4 to 6, and simply eluted with 2 ml of a 1 mol 1(-1) hydrochloric acid solution. The column could tolerate salt concentrations up to 0.5 mol 1(-1), sample flow rates up to 15 ml min(-1), and sample volumes beyond 1000 ml. Matrix ions of Na+, Mg2+ and Ca2+ and potentially interfering ions of Ni2+, Cd2+, Zn2+, Fe3+ and Co2+ with relatively high concentrations did not show any significant effect on the analyte's signal. Preconcentration factors up to 500 and a detection limit of 0.16 microg 1(-1) were obtained for the determination of the analyte by flame AAS. Application of the method to the determination of natural and spiked copper in river water and seawater samples resulted in quantitative recoveries.     

Eutectic salts promote green synthesis of bis(indolyl) methanes

A convenient and rapid method for the electrophilic substitution reaction of indoles with carbonyl compounds has been developed by using deep eutectic solvent as green and reusable catalysts to afford the corresponding bis(indolyl) methanes in excellent yields at room temperature under mild reaction conditions.     

Constraints on the universe as a numerical simulation

The level scheme above the proton threshold in ²⁶Si is crucial for evaluating the ²⁵Al(p, γ)²⁶Si stellar reaction, which is important for understanding the astrophysical origin of the long-lived cosmic radioactivity ²⁶Al(T _1/2 = 7.17 × 10⁵ y) in the Galaxy. The excited states in ²⁶Si have been studied using an in-beam γ-ray spectroscopy technique with the ²⁴Mg(³He, nγ)²⁶Si reaction. γ-rays with energies up to 4.6 MeV emitted from excited states in ²⁶Si have been measured using large volume HPGe detectors. The spin-parity of one of the most important states reported recently at 5890.0keV has been assigned as 0⁺ by γ-γ angular correlation measurements in this work.     

Magnetically assisted solid phase extraction using Fe3O4 nanoparticles combined with enhanced spectrofluorimetric detection for aflatoxin M1 determination in milk samples

A novel, facile and inexpensive solid phase extraction (SPE) method using ethylene glycol bis-mercaptoacetate modified 3-(trimethoxysilyl)-1-propanethiol grafted Fe₃O₄ nanoparticles coupled with spectrofluorimetric detection was proposed for determination of aflatoxin M1 (AFM1) in liquid milk samples. The method uses the advantage fluorescence enhancement by β-cyclodexterin complexation of AFM1 in 12% (v/v) acetonitrile–water and the remarkable properties of Fe₃O₄ nanoparticles namely high surface area and strong magnetization were utilized to achieve high enrichment factor (57) and satisfactory extraction recoveries (91–102%) using only 100 mg of magnetic adsorbent. Furthermore, fast separation time of about 15 min avoids many time-consuming column-passing procedures of conventional SPE. The main factors affecting extraction efficiency including pH value, desorption conditions, extraction/desorption time, sample volume, and adsorbent amount were evaluated and optimized. Under the optimal conditions, a wide linear range of 0.04–8 ng mL⁻¹ with a low detection limit of 0.015 ng mL⁻¹ was obtained. The developed method was applied for extraction and preconcentration of AFM1 in three commercially available milk samples and the results were compared with the official AOAC method.     

Sonochemical synthesis of a novel nano-rod two-dimensional zinc(II) coordination polymer; preparation of zinc(II) oxide nanoparticles by direct thermolyses

A novel mixed-ligand zinc(II) coordination polymer, {[Zn(μ-4,4'-bipy)(μ-3-bpdh)(H(2)O)(2)](ClO(4))(2)·(4,4'-bipy)(0.5)}(n) (1); 3-bpdh=2,5-bis(3-pyridyl)-3,4-diaza-2,4-hexadiene and 4,4'-bipy=4,4'-bipyridine, has been synthesized and characterized by IR, (1)HNMR and (13)CNMR spectroscopy. The single crystal X-ray data of compound 1 shows that this coordination polymer grows in two dimensions by two different bridging ligands, 4,4'-bipy and 3-bpdh. Also, nano-scale of compound 1 has been synthesized by sonochemical method and characterized by IR, X-ray diffraction (XRD) and scanning electron microscopy (SEM). Thermal stability of compound 1 in single crystalline and nano-scale form was carried out by thermal gravimetric (TG) and differential thermal analysis (DTA). The ZnO nanoparticles were obtained by calcination of compound 1 at 500°C under air atmosphere and by thermolyses in oleic acid at 200°C. The zinc(II) oxide nanoparticles were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM).