Effects of ammonium nitrate on sensitivity for determinations of copper,iron, and manganese in sea water by atomic absorption spectrometry with pyrolytically coated graphite tubes

Ammonium nitrate, used as a matrix modifier in sea-water analysis to eliminate the interference of sodium chloride, degrades the pyrolytic coating on graphite-furnace tubes. The initially increased sensitivities for copper, manganese and iron are maintained for up to 15 atomizations; there is then a rapid decline to a constant lower sensitivity. The characteristics depend strongly on the particular lot of furnace tubes. To decrease the NaCl interference without using matrix modifier, estuarine samples must be diluted (1 + 1) with pure water. Blanks and standards are prepared and diluted with Gulf Stream water containing low amounts of trace metals to match the estuarine matrix.     

A new column system for isothermal gas chromatographic analysis of light gases (H2, O2, N2, CO,CH4, CO2, C2H4, C2H6 and C2H2) employing a column switch technique

Summary A new column system for the isothermal analysis of H₂, O₂, N₂, CO, CH₄, CO₂, C₂H₄, C₂H₆ and C₂H₂ is described. Higher hydrocarbons and water are backflushed from the system. The use of 13X molecular sieve in a relatively deactivated state shortens the elution times of the light components and improves peak shapes. Both factors enable quantitative analyses to be carried out satisfactorily at lower concentrations than would otherwise be possible. Analysis of all compounds listed can be carried out in eleven minutes. Sparingly activated 13X molecular sieve columns have proved to be very stable and rarely require reactivation.The method of column switching employed avoids the use of mechanical valves in the sample path and is suitable for automatic operation.

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Neue Trennsäulenkombination für die GC-Analyse von Gasen (H₂, O₂, N₂, CO, CH₄, CO₂, C₂H₄, C₂H₆, C₂H₂) unter Anwendung einer nichtmechanischen Säulenschalttechnik

Zusammenfassung Eine neue Trennsäulenkombination zur isothermen Trennung von H₂, O₂, N₂, CO, CH₄, CO₂, C₂H₄, C₂H₆ und C₂H₂ wird beschrieben. Höhere Kohlenwasserstoffe und Wasser werden rückgespült. Durch Anwendung eines auf relativ niedriger Aktivitätsstufe betriebenen Molekularsiebs 13X wird die Elutionszeit der flüchtigen Komponenten verkürzt und deren Peakform verbessert. Beides erlaubt befriedigende quantitative Analysen im Bereich kleinerer Konzentrationen, als dies mit anderen Systemen möglich ist. Die Analyse eines Gemisches aller oben angeführten Komponenten ist innerhalb von 11 Minuten möglich. Mäßig aktivierte Trennsäulen mit Molekularsieb 13X erwiesen sich als sehr stabil, sie erfordern nur selten eine Reaktivierung. Die hier verwendete Säulenschalttechnik vermeidet die Anwendung mechanischer Umschaltsysteme im Probenweg und ist für eine automatische isotheme Arbeitsweise besonders geeignet.

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Une nouvelle combinaison de colonnes pour l'analyse à température constante, par chromatographie en phase gazeuse, de gaz légers (H₂, O₂, N₂, CO, CH₄, CO₂, C₂H₄, C₂H₆ et C₂H₂) employant un système de commutation de colonnes

Résumé On décrit une nouvelle combinaison de colonnes pour l'analyse à température constante des mélanges de H₂, O₂, N₂, CO, CH₄, CO₂, C₂H₄, C₂H₆ et C₂H₂. Les hydrocarbures à plus grand nombre de carbones et l'eau sont éliminés du système par contrebalayage. L'emploi de tamis moléculaire 13X dans un état de désactivation relativement élevé permet de réduire les temps d'élution des composants légers et de rendre la forme des pics plus favorable. Ces deux facteurs permettent d'effectuer des analyses quantitatives à des concentrations plus basses que celles possibles normalement. L'analyse de tous les composants cités peut être faite en 11 minutes. Les colonnes de Tamis moléculaire 13X à degré d'activation modéré sont très stables et leur réactivation n'est nécessaire qu'après une longue période d'emploi. La méthode de commutation employée pour les colonnes évite l'utilisation de vannes mécaniques sur le parcours de l'échantillon; elle est convenable pour le fonctionnement automatique.

     

Use of mobile phase 18-crown-6 to improve peak resolution between mono- and divalent metal and amine cations in ion chromatography

It is difficult to quantify NH4+ by ion chromatography in the presence of high concentrations of Na+ due to peak overlap. The Dionex IonPac CS15 column, which contains phosphonate, carboxylate, and 18-crown-6 functional groups, was originally developed to overcome this problem. We have found that the addition of 18-crown-6 to the eluent promotes improved peak resolution between Na+ and NH4+ even at concentrations as high as 60,000 to 1 using this column. Its use also improves the separation of alkali and alkaline earth metal and amine cations. Mobile phase 18-crown-6 increased the retention times of CH3NH3+, NH4+, and K+, and decreased the retention time of Sr2+. The retention times of Li+, Na+, Mg2+, Ca2+, (CH3)2NH2+, and (CH3)3NH+ were not affected. This method makes possible the direct analysis of ammonia from nitrogenase, the enzyme responsible for biological nitrogen fixation. The resolution of the NH4+ peak from the Na+ and Mg2+ peaks improved from zero resolution to values of 6.19 and 5.65, respectively. This technique considerably reduces the analysis time of NH4+ in the presence of high concentrations of Mg2+ and Na+ over traditional indophenol measurements.     

Alkyl modified anionic siloxanes as pseudostationary phases for electrokinetic chromatography. I. Synthesis and characterization

Anionic water soluble siloxane polymers have been synthesized and characterized for electrokinetic chromatography. Siloxane polymers are of interest in electrokinetic chromatography because of the wide variety of chemistries that can be developed based on these backbones, including much of the stationary phase chemistry developed in the last 30 years. The siloxanes in this study have a sulfonate functional group. The siloxanes have different length alkyl chains (C8, C12, C18) attached to the backbone in differing densities. The methylene selectivity generally increases with increasing alkyl chain length and with increasing alkyl chain density. The electrophoretic mobility appears to pass through a maximum as more alkyl chain is added to the siloxane backbone. The efficiency also would seem to pass through a maximum as more alkyl chain is added. The chemical selectivities of the siloxane polymers are very different from sodium dodecyl sulfate but are similar to each other.     

Production of Organometallic Polymers by the Interfacial Technique. XXXII. Reaction Variables in the Synthesis of Oligomeric Tin Poly(cobalticinium Esters) and Thermal Properties of the Products

The synthesis of oligomeric tin poly(cobalticinium esters) is presented as a function of the particular reaction variables stirring rate, pH and amount of added base, mole ratio of reactants, concentration of reactants, and volume of organic phase. Factors which decrease the solubility of the stannane apparently act to increase the yield of polyester. The thermal characterization of I was carried out via DSC and TGA. The products generally exhibit endotherms below 150 to 200[ddot]C which may be related to T_g. Above 200[ddot]C, degradation occurs in air by an oxidative mode.     

Miniature Wet-Bulb Technique for Measuring Gas Concentrations in Condensing or Evaporating Systems

Abstract

An analysis is presented to show that a miniature wet-bulb/dry-bulb probe can provide easy, rapid, and accurate point measurements of noncondensable gas concentrations in condensing or evaporating systems. The probe consists of a liquid-soaked porous sphere as small as 0.5 mm in diameter with a fine-gauge thermocouple embedded at its center. Performance of the probe is shown to improve with decreasing wet-bulb size. Measurements of only the total pressure and point wet-bulb temperature are needed to determine the local gas concentration for most gas-vapor systems. The use of the technique in systems with steep concentration gradients is demonstrated by application to the well-studied problem of the gas-loaded two-phase thermosyphon. 195pt