Rapid radiochemical neutron activation analysis for iodine in urine by different separation techniques.

In the present work on radiochemical neutron activation analysis for the determination of iodine in urine samples, the performance of three different radiochemical separation techniques, namely, direct extraction, use of an iodinated ion-exchange resin column and Sch?niger combustion, were intercompared and validated. The practical advantages of the iodinated-resin technique make it most suitable for the rapid routine determination of iodine in urine. It was further verified by participation in an international intercomparison run of urine analysis, and used in a pilot study on iodine determination in the urine of 171 Slovenian schoolchildren, where it gave results in good agreement with the catalytic method.     

In situ sensing of the middle atmosphere with balloonborne near-infrared laser diodes

Since 1997, two near-infrared laser diode sensors have been developed with the support of the CNES, the French space agency, to provide in situ data of H(2)O, CH(4) and CO(2) in the middle atmosphere. The realized instruments were flown from stratospheric balloons within the framework of European campaigns for the study of stratospheric ozone and water vapor and were involved in the validation of the ODIN and ENVISAT satellites. In this paper, we describe the developed laser probing technique, we report atmospheric measurements and finally we discuss future perspectives, particularly the in situ laser sensing of the lower atmosphere of Mars and the implication of the laser hygrometers in balloon campaigns at mid-latitudes and tropical regions to investigate the sources and sinks of stratospheric H(2)O.     

Determination of manganese in grain by potential titration with catalytic end-point indication

A method of catalytic potential titration for the determination of trace manganese by using crystal violet ion selective electrode is reported in this paper. It is based on the catalytic effect of manganese (II) on the oxidation of crystal violet by potassium periodate in the presence of nitrilotriacetic acid (NTA). The experiments indicated that this technique showed high sensitivity and high accuracy. The results of determination of trace manganese in grain could be compared with the results obtained by means of atomic absorption spectrometry.     

Tandem conjugate addition-α-alkylation of unsaturated amides. Synthetic methodology.

1,4-Addition of RLi, RMgX, and (RS) ₂CHLi reagents to unsaturated amides 2a-c followed by α-alkylation is shown to constitute a general and efficient synthetic procedure for the formation of two CC bonds in a single step.     

Pushing the detectability of voltammetry: how low can we go?

The coupling of adsorptive accumulation with catalytic reactions results in remarkably low (sub-picomolar) detection limits. This review assesses various strategies for attaining such dual-amplification effects, that lead to the most sensitive voltammetric technique, adsorptive-catalytic stripping voltammetry (AdCtSV).     

超临界流体萃取-胶束电动毛细管色谱法分离测定大黄中蒽醌类组分的含量

采用ＳＴＥ－ＭＥＣＣ法分离测定大黄中的芦荟大黄素，大黄素和大黄酸。萃取条件为压 力４１．４ＭＰａ，温度５０℃，改性剂量０．４ｍＬ。被测组分在１０ｍｉｎ得到全部分离。本法准确、简 便、快速、结果令人满意。     

Effect of water-soluble cross-linker on the growth and properties of ethyl acrylate–methacrylic acid emulsion opolymer particles

Model ethyl acrylate–methacrylic acid copolymer latices and latices of particles cross-linked by copolymerizing small amounts of water-soluble N,N′-methylenebisacrylamide were prepared by nonseeded semicontinuous emulsion copolymerization. Dynamic and static light scattering measurements indicated a slightly higher degree of polydispersity in the case of cross-linked particles, especially in the initial stages of polymerization. The hydrodynamic volume of the alkalinized particles controlling the viscosity properties of the dispersions decreased with the time of polymerization and in the case of cross-linked copolymer almost reached a constant value at about 1 h. The different character of the particle structure was confirmed by differences in particle disintegration after alkali addition or in the presence of methanol. Received: 2 February 1999/Accepted: 28 June 2000     

The triplet channel in the photodissociation of ozone in the Hartley band: classical trajectory surface hopping analysis

The triplet channel in the photodissociation of ozone in the Hartley band, O3 + hv-->O(3P) + O2(3sigma), is investigated by means of a classical trajectory surface hopping method using ab initio diabatic potential energy surfaces for the B and the R states. Because of the strong recoil in the R state along the breaking O-O bond, O2(3sigma) is produced with a high rotational energy. The nonadiabatic transition probability depends markedly on the coordinate along the crossing seam. As a consequence a unique correlation is found between the internuclear geometry at the crossing and the final vibrational state of O2(3sigma). The calculated distribution of the translational energy is in good accord with the measured distribution.     

Roles of TNF-alpha and IgE in the late phase of contact hypersensitivity induced by trimellitic anhydride

Trimellitic anhydride (TMA) is widely used industrially to make epoxy and alkyd resins, plasticizers and surfactants. The purpose of this study was to investigate whether contact hypersensitivity (CHS) is induced by repeated TMA challenge and the role of TNF-alpha and IgE in the TMA-induced CHS. The repetition of the challenge enlarged the extent of an early and a late phase of CHS in TNF-alpha+/+ (B6129SF2/J) and Balb/c mice. In the late phase of TMA-induced CHS, the peak of ear swelling responses by single challenge showed at 24 h after challenge, but the peak was observed at 8 h after repeated challenge. In the TNF-alpha knockout TNF-alpha-/- (B6;129S-Tnftm1Gk1) mice, the repetition of the TMA challenges enlarged the extent of the late phase of CHS, but less than those in TNF-alpha+/+ mice. Injection of anti-TNF-alpha antibody into the peritoneal cavity of Balb/c mice significantly decreased the extent of the late phase of CHS. Subcutaneous injection of anti-IgE antibody into Balb/c mice also decreased the extent of the late phase of CHS in dose-dependent manner. Histologically, infiltration of polymorphonuclear leukocytes and eosinophils was more pronounced in repeatedly TMA-challenged TNF-alpha+/+ and Balb/c mice than in the TNF-alpha-/- mice and anti-TNF-alpha or anti-IgE antibodies treated Balb/c mice. These results indicate that mice sensitized by TMA could possibly offer a useful model to study the mechanism of CHS, and TNF-alpha and IgE may act as potential modulators in the late phase of TMA-induced CHS. Neutralization of TNF-alpha and IgE by anti-TNF-alpha or anti-IgE antibodies may provide therapeutic tools for the treatment of TMA-induced CHS.