Derivatization procedures for the detection of estrogenic chemicals by gas chromatography/mass spectrometry

This work evaluated derivatization procedures for detecting both natural and synthetic estrogenic chemicals by gas chromatography/mass spectrometry (GC/MS). Different silylating agents, mainly trimethylsilylating (TMS) agents, were compared, and the roles of various content of trimethylchlorosilane (TMCS, as a stimulator) were investigated. The difference in the abundances of the derivatives was caused by the steric hindrance of multiple hydroxyl groups and ethynyl groups in the structures of estrogenic chemicals. The use of TMCS produces an increase in the derivatization yield, especially for the compounds with multiple hydroxyl groups (i.e., 17beta-estradiol (E(2)) and estriol (E(3))). Mass spectra of O-TMS derivatives and tentative fragmentation profiles are proposed. Molecular ions were the base peaks for all the derivatives, and were used as the quantitation ions to obtain maximum detection sensitivity and specificity. Sample enrichment was achieved by Oasis HLB solid-phase extraction cartridges. The quantitation limits of these compounds ranged from 5 to 10 ng/L in 1000-mL water samples. Recovery of the estrogenic chemicals in spiked various water samples ranged from 78 to 102% while relative standard deviation (RSD) ranged from 1 to 15%.     

The formation of a compact polymer film on a copper electrode from benzimidazole solution

The effects of the pretreatment of copper in benzimidazole solutions on the anodic reactions have been observed. The structures of the chemisorbed benzimidazole on copper were studied by using the infrared reflection-absorption technique and X-ray photoelectron spectroscopy. It was found that a compact film of benzimidazolato copper(I) was formed on the copper surface when copper was immersed in a stirred benzimidazole solution and cyclic voltammetry applied. This compact polymer film inhibited anodic oxidation effectively.     

钙与 DBC-偶氮氯膦显色反应的研究及其在高纯氧化钇中钙的测定的应用

在PH8.5-9的液中,钙可与DBC-偶氮氯膦形成一种紫色的稳定配合物。该配合物在625nm处有最大吸收,表观摩尔吸光系数为2.6×10~4L.mol~(-1).cm~(-1),配合物组成为Ca:DBC-偶氮氯膦=1:1。在Zn-DTPA和乙二胺的存在下,较大量的Y~(3+)、Fe~(3+)及Cu~(2+)、Mo(Ⅵ)、Cr~(3+)等三十余种离子不干扰钙的测定。方法的选择性较好,利用本方法,并经简单萃取分离基体后,测定了高纯氧化钇和易切削钢中的微量钙,结果令人满意。标准加入试验回收率好。方法简便实用。     

Energy transfer as a function of collision energy. I Collision partners: Hydrogen halides + inert gases,hydrogen halides,H2S and propane

Infrared emission has been recorded from a heated seeded supersonic primary beam of HCl or HF (1) prior to collision with a target beam, and (2) subsequent to that collision. Mean collision energy and collision partner were varied systematically. After correction for elastic scattering, the net population change due to inelastic scattering in a translation—rotation (T ? R) energy-transfer encounter was obtained for specific J states ranging from J = 0–16 of vibrational level υ = 1 of the primary-beam molecule. The broad picture is that a net transfer into low-J states out of higher-J states takes place at low collision energies, and the converse at high collision energies. These observations are interpreted in terms of the “exponential model” for the relative cross sections of T ? R inelastic collisions, S^R (J_i → J_f), proposed earlier [J.C. Polanyi and K.B. Woodall, J. Chem. Phys. 56 (1972) 1563], modified here to satisfy microscopic reversibility. The constant C in the model, which governs the exponential decrease in S^R with increasing energy difference ΔE_J between J_f and J_i, can be derived, as a function of collision energy T, from the present experimental data; C decreases as T increases, i.e. larger ΔJ become more probable. In order to check the validity of the model, it was compared with 3D trajectory results; according to this criterion it was found to give a very good representation of S^R(J_i → J_f) with a single value for C, within a limited range of J_i. The collision partners HCl + HF exhibit anomalously efficient rotational deactivation; evidence is presented which indicates that at low collision energies this is due to resonant R → R transfer. Very efficient deactivation of HCl by HCl, at low collision energy, is likely to be due to V — V transfer.     

Neutron activation analysis of gold and iridium in steel

A method of determination of trace gold and iridium in steel is presented. The samples were preconcentrated with an anion exchanger. The chemical recoveries were determined by an isotope tracer technique using¹⁹⁸Au and¹⁹²Ir.     

A small molecule with osteogenesis-inducing activity in multipotent mesenchymal progenitor cells

Purmorphamine, which is a 2,6,9-trisubstituted purine compound, was discovered through cell-based high-throughput screening from a heterocycle combinatorial library. It differentiates multipotent mesenchymal progenitor cells into an osteoblast lineage. It will serve as a unique chemical tool to study the molecular mechanisms of osteogenesis of stem cells and bone development.     

Application of Liquid Crystalline NMR Solvents to a Mixture of Ketones

A series of dilute liquid crystalline solvents are used to study the effect of slight anisotropy caused by partial alignment on chemical shift and residual dipolar coupling (RDC) in small molecules. The residual dipolar couplings between protons in solutes are found to be almost independent of the local environment. It is also found that the chemical shift does not change over the concentration range observed. A linear relationship between residual dipolar coupling and liquid crystal concentration is observed at relatively low concentrations, but is severely violated at high concentrations.     

Investigation of the hydrogen bonds between formaldehyde and hydrogen halides by pseudopotential Ab Initio method

The weak hydrogen bonded systems H₂CO ?HX (X = F, Cl, Br, and I) have been studied by means of ab initio MO method with pseudopotential approximation. The stabilization energies of these hydrogen bonds are 8.96, 4.12, 3.00, and 2.21 kcal/mol, respectively. The interaction eneraction energies are farther decomposed according to Morokuma's energy decomposing scheme. It is found that the title complexes are mainly electrostatic, although the contribution of charge transfer is also significant.     

Theoretical study on structures and stability of C4P isomers

The structures, energetics, spectroscopies, and stabilities of doublet C(4)P isomeric species are explored at the DFT/B3LYP, QCISD, and CCSD(T) (singlet-point) levels. A total of 12 minimum isomers and 27 interconversion transition states are located. At the CCSD(T)/6-311G(2df)//QCISD/6-311G(d)+ZPVE level, the lowest-lying isomer is a floppy CCCCP 1 (0.0 kcal/mol) mainly featuring a cumulenic structure |C=C=C=C=P*|, which differs much from the analogous C4N radical (|*C-C[triple bond]C-C[triple bond]N|). The quasi-linearity and the low bending mode of 1 are in contrast to the previous prediction. The second energetically followed isomer PC-cCCC 3 (14.9 kcal/mol) possesses a CCC ring-bonded to CP. The two low-lying isomers are separated by a high-energy ring-closure/open transition state (26.5 kcal/mol) and thus are very promising candidates for future laboratory and astrophysical detection. Furthermore, four high-energy isomers, that is, two bent isomers CCPCC 2 (68.4 kcal/mol) and CCPCC 2' (68.5 kcal/mol) and two cagelike species 10 (56.0 kcal/mol) and 11 (67.9 kcal/mol), are also stabilized by considerable barriers. The present work is the first detailed potential energy survey of CnP clusters and can provide useful information for the investigation of larger CnP radicals and for understanding the isomerism of P-doped C vaporization processes.     

Hydroxylamine Derivative in Purex Process III. The Kinetics of Oxidation-reduction Reaction Between N,N-diethylhydroxylamine and Neptunium(VI)

The kinetics of oxidation-reduction reaction between N,N-diethylhydroxylamine (DEHAN) and neptunium (VI) in nitric acid media has been studied by spectrophotometry at 25.2 °C. The rate equation is -d[Np(VI)/dt=k[Np(VI)][DEHAN]/[H⁺] found by investigating the influence of concentration, acidity, ionic strength and temperature on the reaction. The rate constant of the reaction k is 23.0±1.8 min^–1 for = 2.0 mol/l. A possible mechanism of reaction has been suggested according to the ESR spectra of nitroxide radical produced in the DEHAN+V(V) system.