Isotopic composition and concentration measurements of atmospheric CO2 with a diode laser making use of correlations between non-equivalent absorption cells

Correlations between a sample and a sealed reference cell of a tunable diode laser spectrometer for the measurement of the isotopic composition (δ ¹³C) and the concentration of atmospheric carbon dioxide in air have been investigated. Likely due to fluctuations of the laser emission profile, these correlations have been used to improve the performance of the instrument. In a comparison with isotope ratio mass spectrometer and gas chromatographic measurements, an accuracy of 0.15‰ for δ ¹³C and 0.05 ppmv for the CO₂ concentration is demonstrated for 40 s integration time. Long-term stability and field deployment of the instrument have been investigated during a few days measurement campaign in Paris.     

Factors that control zeolite L crystal size

Time-series hydrothermal syntheses from two organic-cation-free gels with different compositions were employed to study the factors that control the final size of zeolite L crystals. The first gel had a starting K/Al ratio of 10, whereas in the second one it was three times lower. The relatively simple chemical composition of the starting gels and the combination of complementary characterization methods allowed us to track down the different stages of transformation of the initial amorphous gels into zeolite crystals and the factors that control the nucleation and growth processes. The role of the starting mixture components in the formation of the primary amorphous particles was explored. It was found that the profoundly different reaction kinetics in the two systems are caused by the difference in diffusion rates, which in turn are controlled by the extent of the polymerization reactions at room temperature during mixing of the starting components prior to hydrothermal treatment. As a consequence, nucleation is fast and ubiquitous in the first system with higher water content and K/Al ratio, whereas it is slow and sporadic in the second system with lower water content and K/Al ratio. Ultimately, these differences in the kinetics lead to the formation of two distinctly different patterns of crystal-size distribution, with a large number of small nanocrystals in the first sample and fewer large crystals in the second sample. The new findings put zeolite crystal growth on a rational basis that would enable the control of zeolite crystal size in similar organic-template-free systems.     

Solid-state NMR investigation on the interactions between a synthetic montmorillonite and two homopolypeptides

Interactions of two homopolypeptides (polylysine and polyglutamic acid) with a synthetic montmorillonite were studied by ¹H MAS, ¹H–²⁷Al HETCOR and ¹H–¹³C CP-MAS NMR experiments. ¹H–²⁷Al HETCOR with ¹H spin-diffusion NMR appears to be a powerful probe for the identification of the polypeptide fragments, which interact with the montmorillonite interlayer surfaces. In particular, selective interactions were observed between the polypeptide side-chains and the montmorillonite octahedral aluminum atoms. ¹H–¹³C CP-MAS NMR experiments were used to assess the dynamics of the two polypeptides through the measurement of the t_1/2 characteristic time of selected carbons. Results indicate that the local mobility of the side chains and their interaction with the montmorillonite layers depend on the nature of the adsorbed polypeptides.     

The First Synthesis of Organic Diselenolates: Application to the Synthesis of Diorganyl Diselenides

The addition of elemental selenium to organolithium compounds 1 or organic selenates 2 gives organic diselenolates 3 . The reactions proceed by the insertion of two selenium atoms into the carbon–metal bonds or of one selenium atom into a selenolate. Evidence for the existence of n-butyldisilenol has also been obtained.     

Recent developments in X-UV optics and X-UV diagnostics

Metrology of XUV beams (X-ray lasers, high-harmonic generation and VUV free-electron lasers) is of crucial importance for the development of applications. We have thus developed several new optical systems enabling us to measure the optical properties of XUV beams. By use of a Michelson interferometer working as a Fourier-transform spectrometer, the line shapes of different X-ray lasers have been measured with a very high accuracy (/10^-6). Achievement of the first XUV wavefront sensor has enabled us to measure the beam quality of laser-pumped as well as discharge-pumped X-ray lasers. A capillary discharge X-ray laser has demonstrated a very good wavefront allowing us to achieve an intensity as high as 3×10¹⁴ Wcm^-2 by focusing with a f=5 cm mirror. The sensor accuracy has been measured using a calibrated spherical wave generated by diffraction. The accuracy has been estimated to be as good as /120 at 13 nm. Commercial developments are underway. At Laboratoire dOptique Appliquée, we are setting up a new beamline based on high-harmonic generation in order to start the femtosecond, coherent XUV optic . PACS 07.85.Nc;32.70.Jz;41.50.+h;42.15.Dp;42.55.Vc;52.70.La     

LCEC-determination of urinary normetanephrine, metanephrine and 3-methoxy-tyramine

Summary A specific and sensitive analysis of urinary normetanephrine (NMN), metanephrine (MN) and 3-methoxy-tyramine was performed using reversed phase high-performance liquid chromatography coupled with an electrochemical detector. Spectrophotometric methods are insensitive in the normal and low abnormal ranges. The catecholamine method employed, is based on a modification of BioRad Laboratories procedure [1] and the method of Shoup and Kissinger [2]. Utilizing a single cation-exchange resin, the catecholamines are eluted with boric acid and purified by adsorption on alumina. The metanephrines are separated from other urinary constituents by elution with ammonia from the same chromatographic column. The recovery average was 74% for normetanephrine, 65% for metanephrine and 78% for 3-methoxy-tyramine of added standards. The quantitative detection based on electrochemical reactivity provides a simple and accurate analytical technique for routine application.

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LCEC-Bestimmung von Normetanephrin, Metanephrin und 3-Methoxy-tyramin in Harn

Zusammenfassung Eine spezifische und empfindliche Bestimmung der genannten Verbindungen wurde mit Hilfe der Umkehrphasen-HPLC mit elektrochemischer Detektion durchgeführt. Spektralphotometrische Verfahren sind für normale und niedrigere Gehalte nicht geeignet. Das benutzte Catecholaminverfahren beruht auf einer Modifikation der Methode der BioRad Laboratories [1] und des Verfahrens nach Shoup u. Kissinger [2]. Mit Hilfe eines Kationenaustauschers werden die Catecholamine abgetrennt, mit Borsäurelösung eluiert und an Aluminiumoxid gereinigt. Die Metanephrine werden durch Elution mit Ammoniaklösung abgetrennt. Die durchschnittliche Wiedergewinnung betrug 74% für Normetanephrin, 65% für Metanephrin und 78% für 3-Methoxy-tyramin. Die elektrochemische Detektion ermöglicht eine einfache Anwendbarkeit bei Routineuntersuchungen.