Q value related mass determinations using a Penning trap

We report here about measurements of reaction and decay Q values by precise determination of pairs of atomic masses. These were performed with the Penning trap mass spectrometer SMILETRAP. Measurements with Penning traps give reliable and accurate masses, in particular Q values, due to the fact that certain systematic errors to a great deal cancel in the mass difference between the two atoms defining the Q value. Some Q values that are of fundamental interest will be discussed here, for example, a new Q value for the ⁶Li (n,γ) ⁷Li reaction, for the β-decay of tritium, related to properties of the electron neutrino mass, and for the neutrino-less double β-decay of ⁷⁶Ge, related to the question of whether the neutrino is a Majorana particle or not. In case of the latter two we report the most accurate Q values, namely 18,589.8(12) eV for the tritium decay and 2,038.997(46) keV for the neutrino-less double β-decay of ⁷⁶Ge.     

Determination of phenol and catechol concentrations with oxygen probes coated with immobilized enzymes or immobilized cells

The enzyme phenol 2-hydroxylase was immobilized on Sepharose and used in conjunction with an O₂ electrode for quantitating phenol. Similarly, catechol 1,2-oxygenase was used for quantitating catechol. A third probe was prepared by immobilization ofTrichosporon cutaneum cells rather than purified phenol 2-hydroxylase for phenol quantitation. The whole cell system gave results comparable to the immobilized enzyme system.     

A dual fluorophore system for simultaneous bioassays

A detection scheme for the simultaneous evaluation of two bioassays based on fluorescence spectroscopy is presented. For the determination of hydrogen peroxide-generating enzymes or peroxidases, the non-fluorescent 4-(N-methylhydrazino)-7-nitro-2,1,3-benzooxadiazole (MNBDH) is converted to the strongly fluorescent 4-(N-methylamino)-7-nitro-2,1,3-benzooxadiazole (MNBDA). Phosphatases are detected based on the cleavage of the non-fluorescent 5-fluorosalicyl phosphate (5-FSAP) under formation of the fluorescent 5-fluorosalicylic acid (5-FSA). While excitation of the fluorophores may be carried out at the same wavelength, their emission spectra differ significantly. This allows the read-out of both assays using commercially available microplate readers without additional chemometric tools. Compared with individual assays, limits of detection are similar, and linearity of the calibration functions for both enzymes is observed over 2-3 concentration decades starting at the limit of quantification. The simultaneous determination of glucose oxidase and acid phosphatase in honey is presented as example for the application of the detection scheme.     

Determination of trace metals in industrial boron carbide by solid sampling optical emission spectrometry. Optimization of DC arc excitation (current, atmosphere and chemical modifier)

Graphite arc emission spectrometry has become possible as a result of the invention of novel types of optical spectrometers with Echelle-optics and semiconductor array detectors, and by the application of electronically controlled, high current arc generators. An optimization of the excitation parameters to boron carbide analysis is reported here, measuring background corrected line intensities that were integrated for the time of total evaporation of 5 mg boron carbide sample with or without added chemical modifiers. The following set of experimental conditions were compared with respect of analytical sensitivity and precision: (A) no modifier, Ar + O₂ (20%), 16 A; (B) sample + graphite powder (1 + 1), Ar + O₂ (20%), 16 A; (C) sample + CaF₂ (1 + 1), Ar, 25 A; (D) sample + CaF₂ + graphite powder (1 + 1 + 1), Ar, 25 A. The graphite powder modifier resulted in improved precision in general, and the CaF₂ was effective as a plasma ionization buffer and fluorinating agent. The best compromise was found under conditions B, when oxygen was present in the discharge atmosphere. This is likely due to the stepwise conversion of the boron carbide matrix to the more volatile boron oxide. Under conditions B, detection limits in the ranges of 0.3–9 μg g⁻¹ for Al, Ca, Cr, Cu, Fe, Mg, Mn and Si and that of 18–38 μg g⁻¹ for Ti, W, and Zr were attained. Average RSDs of 10.2 and 9.7% were found, respectively, without and with internal referencing to boron.     

Recent Developments in Flow Injection/Sequential Injection Liquid-Liquid Extraction for Atomic Spectrometric Determination of Metals and Metalloids

Abstract

This review aims to provide a critical overview of automated flow injection and sequential injection liquid-liquid extraction for preconcentration and/or separation of ultra-trace metal and metalloid species hyphenated with atomic spectrometric detection systems, including some new trends and applications in the subbranches of cloud point extraction (CPE), wetting film extraction (WFE), supported liquid membrane extraction (SLME), extraction chromatography (EChr), and liquid-phase microextraction (LPME) techniques. The analytical performance of flow-injection/sequential injection liquid-liquid extraction methods is markedly affected by the components of the flow network such as segmentor, extraction coil, and phase separator. Thus, an overall presentation of system components along with some novel strategies for interface with atomic spectrometers is discussed and exemplified with selected applications.     

Macrocyclic Polyethers as Enolate Activators in Homogeneous and Heterogeneous Systems

Abstract

The ability of macrocyclic polyethers to activate enolates has been studied in the alkylation of de-oxybenzoin (1) with butyl derivatives nBuY (Y = Br, I, OMes) catalyzed by crown ether PHDB18C6 (7) or cryptand [2.2.2,C10] (8) under phase-transfer catalysis (PTC) and homogeneous (chlorobenzene) conditions. The enolate reactivity is mainly determined by the ligand (cryptand > crown ether) and solvent (increasing with the polarity, in the order: toluene < chlorobenzene < 1,2dichlorobenzene). Regioselectivity of the reaction is also remarkably affected by ligand and alkylating agent.     

单元和多元取代纳米氢氧化镍晶相及其结构稳定性研究

以硝酸镍为镍源,硫酸钴、硫酸铜、硫酸铝为掺杂原料,采用超声波辅助沉淀法分别制备了单元和多元取代纳米氢氧化镍。用X射线衍射（XRD）、傅里叶变换红外光谱（FTIR）、激光粒度仪（PSD）及电子显微镜（TEM、SEM）对样品晶相结构、形貌、粒度分布等进行了表征,研究了单元或多元取代对产物晶相及其结构稳定性的影响。结果表明,样品均为纳米级Ni（OH）₂,随着掺杂元素种类的增多,其一次粒子变得细小,团聚加重,二次粒子粒径增大。样品中α-Ni（OH）₂比例随取代元素增多而增大。相对于Co单元和Co/Cu双元取代,Co/Cu/Al三元取代的样品其晶相结构更稳定,在碱液中浸泡3周后仍为纯α-Ni（OH）₂。在相同掺杂比例下,Cu取代比Co取代更有利于α-Ni（OH）₂的生成,但Co取代的样品结构稳定性优于Cu取代的样品。     

Cloud point extraction for the determination of cadmium and lead employing sequential multi-element flame atomic absorption spectrometry

A cloud point extraction procedure for pre-concentration and determination of cadmium and lead in drinking water using sequential multi-element flame atomic absorption spectrometry is described. 4-(2-thiazolylazo)-orcinol (TAO) has been used as complexing agent and the micellar phase was obtained using the non-ionic surfactant octylphenoxypolyethoxyethanol (Triton X-114) and centrifugation. The conditions for reaction and extraction (surfactant concentration, reagent concentration, effect of incubation time, etc) were studied and the analytical characteristics of the method were determined. The method allows the determination of cadmium and lead with quantification limits of 0.30?µg?L^?1 and 2.6?µg?L^?1, respectively. A precision expressed as relative standard deviation (RSD, n?=?10) of 2.3% and 2.6% has been obtained for cadmium concentrations of 10?µg?L^?1 and 30?µg?L^?1, respectively, and RSD of 1.3% and 1.7% for lead concentrations of 10?µg?L^?1 and 30?µg?L^?1, respectively. The accuracy was confirmed by analysis of a natural water certified reference material. The method has been applied for the determination of cadmium and lead in drinking water samples collected in the cities of Ilhéus and Itabuna, Brazil. Recovery tests have also been performed for some samples, and results varied from 96 to 105% for cadmium and 97 to 106% for lead. The cadmium and lead concentrations found in these samples were always lower than the permissible maximum levels stipulated by World Health Organization and the Brazilian Government.     

ICP-OES法测定镍铬合金中Si，Mn，Fe，Ti，Al，Cu多种元素

建立了电感耦合等离子体发射光谱法测定镍铬合金中Si,Mn,Fe,Ti,Al,Cu元素含量的分析方法。确定了溶样方法和分析谱线,采用基体匹配消除干扰。对方法精密度和准确度进行实验,实验结果表明,各元素的相对标准偏差均小于3%,加标回收率在86.8%～106.9%,镍铬合金标准物质的各元素测定结果均与标准值一致。所建立的方法快速、准确,适用于镍铬合金中多元素同时测定。