Pentafluorophenylboron halides: 40 years later

The pentafluorophenylboron halides C₆F₅BX₂ (X=Cl, F) and (C₆F₅)₂BCl were first reported in the early 1960s. After a period of inactivity these perfluoroarylboron derivatives have been employed for the synthesis of a variety of important compounds, including monomeric iminoboranes, a highly electrophilic hydroboration reagent, strong Lewis acids (with one or two acceptor sites) that activate alkyl metallocene polymerization catalysts, and the first organoxenon(IV) compounds. These recent developments provide a cogent example of the time lag that often occurs between discovery and applications in fundamental research.     

Managed bioremediation of soil contaminated with crude oil soil chemistry and microbial ecology three years later

Analysis of samples taken from three experimental soil lysimeters demonstrated marked long-term effects of managed bioremediation on soil chemistry and on bacterial and fungal communities 3 yr after the application of crude oil or crude oil and fertilizer. The lysimeters were originally used to evaluate the short-term effectiveness of managed (application of fertilizer and water, one lysimeter) vs unmanaged bioremediation (one lysimeter) of Michigan Silurian crude oil compared to one uncontaminated control lysimeter. Three years following the original experiment, five 2-ft-long soil cores were extracted from each lysimeter, each divided into three sections, and the like sections mixed together to form composited soil samples. All subsequent chemical and microbiological analyses were performed on these nine composited samples. Substantial variation was found among the lysimeters for certain soil chemical characteristics (% moisture, pH, total Kjeldahl nitrogen [TKN], ammonia nitrogen [NH₄-N], phosphate phosphorous [PO₄-P], and sulfate [SO₄ ⁻²]). The managed lysimeter had 10% the level of total petroleum hydrocarbons (TPH-IR) found in the unmanaged lysimeter. Assessment of the microbial community was performed for heterotropic bacteria, fungi, and aromatic hydrocarbon-degrading bacteria (toluene, naphthalene, and phenanthrene) by dilution onto solid media. There was little difference in the number of heterotrophic bacteria, in contrast to counts of fungi, which were markedly higher in the contaminated lysimeters. Hydrocarbon-degrading bacteria were elevated in both oil-contaminated lysimeters. In terms of particular hydrocarbons as substrates, phenanthrene degraders were greater in number than naphthalene degraders, which outnumbered toluene degraders. Levels of sulfate-reducing bacteria seem to have been stimulated by hydrocarbon degradation.     

Multiple bonds to silicon: 20 years later

The discovery of stable compounds containing SiC and SiSi bonds in 1981 led to the overturning of the ‘double bond rule’, and paved the way for the recent explosive growth in multiple bond chemistry of the heavier elements. This paper traces the events leading up to the 1981 discoveries, summarizes some of the developments in multiply-bonded silicon chemistry since that date, and outlines challenges for further research in this area.     

80 years of mass spectrometry

The versatility of mass spectrometry can be said to surpass that of any other instrumental method for the analysis of organic and inorganic compounds. In this article, Professor John Beynon traces the instrumental development of mass spectrometry from the early work of J.J. Thomson, who demonstrated its validity as a measuring technique, to the latest advances.     

Homogeneous and heterogeneous micropore structures in carbonaceous adsorbents--twenty years later

The major aim of this study is to show that, developed by Dubinin and Stoeckli, the relation between the parameters of DA (Dubinin-Astakhov) and DRS (Dubinin-Radushkevich-Stoeckli) equations is an approximation. It is shown that the parameter B(0) of DRS isotherm should be taken into account in such a relationship; strictly speaking, the parameter n(DA) of DA adsorption isotherm equation is not only the function of the dispersion of the heterogeneity of carbon, it also depends on the location of the maximum of the distribution of this heterogeneity. Moreover, taking into account that the DR isotherm rather does not describe the adsorption in a homogeneous micropore system, the analogous relationship, however, for DA adsorption isotherm as a local equation in GAI (General Adsorption Isotherm) is proposed.     

Germanium/phosphorus cage compounds with germanium in three different oxidation states

Novel germanium/phosphorus cage compounds with new structural motifs have been synthesized containing germanium in three different oxidation states. The key to obtain this new class of compounds is the use of monolithiated primary phosphine LiHPtBu in the reaction with GeX(2).     

Fifty years of atomic absorption spectrometry

The history of atomic absorption spectrometry (AAS) for the 50 years since the publication of the fundamental paper by Alan Walsh The application of atomic absorption spectra to chemical analysis is presented. The main steps in the development of flame and electrothermal AAS, from the original idea to its introduction as a well-known method of instrumental analysis, are followed. The current status of AAS and the possible directions of its further development are considered.__________Translated from Zhurnal Analiticheskoi Khimii, Vol. 60, No. 4, 2005, pp. 434–446.Original Russian Text Copyright © 2005 by Lvov.     

Using arc-excitation atomic emission spectrometry in studying the microelement composition of bottom sediments

A procedure is developed for the simultaneous determination of trace metals in river, sea, and lake bottom sediments by atomic emission spectrometry. A present-day scenario using a new system of spectrum record and universal buffer mixtures ensures sufficiently reliable results of analysis of samples of complex composition.     

Germanium determination by flame atomic absorption spectrometry: an increased vapor pressure-chloride generation system

A new chloride generation system was designed for the direct, sensitive, rapid and accurate determination of the total germanium in complex matrices. It was aimed to improve the detection limit of chloride generation technique by increasing the vapor pressure of germanium tetrachloride (GeCl₄). In order to do so, a novel joint vapor production and gas-liquid separation unit equipped with a home-made oven was incorporated to an ordinary nitrous oxide-acetylene flame atomic absorption spectrometer. Several variables such as reaction time, temperature and acid concentration have been investigated. The linear range for germanium determination was 0.1-10 ng mL⁻¹ for 1 mL sampling volume with a detection limit (3 s) of 0.01 ng mL⁻¹. The relative standard deviation (RSD) was 2.4% for nine replicates of a 1 ng mL⁻¹ germanium solution. The method was validated by the analysis of one non-certified and two certified geochemical reference materials, respectively, CRM GSJ-JR-2 (Rhyolite), and GSJ-JR-1 (Rhyolite), and GBW 07107 (Chinese Rock). Selectivity of the method was investigated for Cd²⁺, Co²⁺, Cu²⁺, Fe³⁺, Ga³⁺, Hg²⁺, Ni²⁺, Pb²⁺, Sn²⁺, and Zn²⁺ ions and ionic species of As(III), Sb(III), Te(IV), and Se(IV).     

Atomic fluorescence flame spectrometry using a mercury line source

The possibility of exciting the fluorescence of several elements with the “overlapping” lines of other elements and the effectiveness of exciting the fluorescence of Fe, Mn, Ni, Cr, Tl, Cu and Mg with a 90 W mercury discharge lamp, are discussed. A method of increasing the fluorescence radiation by suitable optics, with a simple adaptation of a Jarrell-Ash AA spectrometer, is described. A two-pass system of the incident radiation into the flame is coupled with a mirror, in the optical axis, which reflects the fluorescence radiation emitted at the opposite side to the monochromator slit. This produces an increase of 168% of the signal. Detection limits for 10 elements are reported.     

G-quartets 40 years later: from 5'-GMP to molecular biology and supramolecular chemistry

Molecular self-assembly is central to many processes in both biology and supramolecular chemistry. The G-quartet, a hydrogen-bonded macrocycle formed by cation-templated assembly of guanosine, was first identified in 1962 as the basis for the aggregation of 5'-guanosine monophosphate. We now know that many nucleosides, oligonucleotides, and synthetic derivatives form a rich array of functional G-quartets. The G-quartet surfaces in areas ranging from structural biology and medicinal chemistry to supramolecular chemistry and nanotechnology. This Review integrates and summarizes knowledge gained from these different areas, with emphasis on G-quartet structure, function, and molecular recognition.     

液相色谱-电喷雾电离质谱法检测尿液中的3种合成类固醇药物

研究建立了合成类固醇药物群勃龙、四氢孕三烯炔酮和孕三烯酮的液相色谱-电喷雾质谱的检测方法。尿样经过β-葡萄糖醛酸酶酶解和叔丁基甲醚提取后,采用Zorbax SB-C18分析柱(150 mm×2.1 mm,5 μm),在流动相为pH 3.5的甲酸铵缓冲液-乙腈的条件下进行梯度洗脱,在正离子模式下检测。考察了不同的质谱条件对这类化合物检测结果的影响。建立了人尿液中合成类固醇药物的液相色谱-电喷雾电离质谱的初筛和确证方法。     

Lipid mass spectrometry: A path traveled for 50 years

In the middle of the 1960s, I began graduate school and at the same time started on the path of using mass spectrometry to gain insight into various aspects of lipid biochemistry. This was not a straight path but one that went from organic geochemistry, to lunar sample analysis, to a pursuit of the structure of an elusive and very active, lipid mediator slow reacting substance of anaphylaxis (SRS‐A). The discovery of the structure of SRS‐A opened important questions about phospholipid biochemistry and the arachidonate cycle in cells. I have written this reflection to highlight the various advances in mass spectrometry that occurred during this time that had a great impact on our ability to study lipid biochemistry. I specifically applied these new advances to studies of leukotriene biosynthesis in vivo, leukotriene metabolism, and arachidonate‐containing phospholipids that are essential in providing arachidonic acid for the 5‐lipoxygenase pathway. Along the way, imaging mass spectrometry was shown to be a powerful tool to probe lipids as they exist in tissue slices. We found this as just one of the ways to use the emerging technology of lipidomics to study human pathophysiology. Our studies of neutral lipids and oxidized phospholipids were especially challenging due to the total number of molecular species that could be found in cells. Many challenges remain in using mass spectrometry for lipid studies, and a few are presented.     

Capillary electrophoresis-mass spectrometry: 15 years of developments and applications

Since its introduction in 1987, capillary electrophoresis-mass spectrometry (CE-MS) has developed to a well accepted multidimensional analytical approach complementary and/or competitive to classical MS-hyphenated separation techniques. The threefold combination of rapid developments of an exceptional separation technique, of selective mass detection possibilities, and of very mild ionization modes first allowed these progresses. This article shows the CE specificities that need to be well controlled/known, compared to classical and more routinely used liquid chromatography in the light of its coupling to MS. The major trends and developments over the last 15 years and most of the reviews and applications found in ISI Web of science and publisher databases are presented in a tabulated way. The reader can thus rapidly find existing CE-MS analysis techniques in his field of research and application (forensics, environment, bioanalytics, pharmaceutics, and metabolites).     

Twenty years of interface development for capillary electrophoresis-electrospray ionization-mass spectrometry

Capillary electrophoresis-electrospray ionization-mass spectrometry has the potential to become a preferred tool for the analysis of biological mixtures and other complex samples. The development of improved interfaces in the past twenty years has been critical in demonstrating the feasibility of this technique. However, a compromise still exists between interfaces that give optimal performance and those that are practical for commercial applications. The first section of this review focuses on the technological advances in CE-ESI-MS as they relate to the key interface features for both sheath-flow and sheathless systems: delivery of the sheath liquid, shaping of the emitter tip, formation of electrical contact, and practicality in terms of ease of use and lifetime. In the second section, we review the fundamental processes that affect interface performance. Because of the complex natures of both capillary electrophoresis and electrospray ionization, flow rate, arrangement of the electrical circuit, electrochemistry, tip geometry and location of electrical contact must all be carefully managed in the design of a successful interface.     

Dissolved butyltins in marine waters of the netherlands three years after the ban

In 1990 the Dutch government banned the use of tributyltin-containing antifouling paint for ships up to 25m long. Concentrations of dissolved (<0.45 μm) tributyltin and its degradation products di- and mono-butyltin were determined in six selected marinas during three consecutive years with a frequency of five times a year, starting in 1990. The highest butyltin concentrations were found in Scharendijke located in the salt water lake Grevelingen: up to 2500 ng dm^?3. In tidal-water marinas butyltin concentrations were in the order of 50–300 ng dm^?3, depending on the boating and dredging activity. In some marinas higher butyltin concentrations were found during the summer period, probably indicating the illegal use of tributyltin-containing antifouling paints. No clear trend of decrease in dissolved tributyltin concentrations in the different marinas has been found. Due to the equilibrium between the butyltins dissolved in the water and the butyltins adsorbed onto the sediment, water concentrations will remain more or less constant.