Multicomponent analysis with a computerized flow injection system using LED photometric detection

An original computer-controlled solid-state photometer has been developed and its potential for simultaneous multicomponent flow-injection analysis of binary and ternary mixtures is demonstrated. The device is simple in construction. Its principle of operation is based on rapid sequential measurements of the absorbance of the complexes formed by the analytes with chromogenic reagents at the wavelengths corresponding to the emission maxima of three light emitting diodes (563, 580 and 638 nm).     

Electron scattering on C6F6 and SF6 molecules

Total absolute cross sections for electron scattering on hexafluorobenzene, C₆F₆, and sulfur hexafluoride, SF₆, molecules, have been measured as a function of impact energy from 0.6 to 250 eV. The total cross section for C₆F₆ exhibits a very broad peak stretching from 10 to 100 eV with some weak features near 9.5 and 15 eV superimposed on the peak. Apart from the well-known low-energy resonant structures in the SF6 total cross section function, a new weak resonant feature close to 25 eV has been noticed in the present experiment, in accordance with earlier theoretical calculations.     

Untersuchung der Absorption der bei der Verbrennung phosphororganischer Verbindungen entstehenden P-Oxide mittels32P-markierter Verbindungen

Zusammenfassung Bei der Pyrolyse phosphor-organischer Verbindungen in Sauerstoffatmosphäre bilden sich P-Oxide, die die C,H-Bestimmung stören. Deren Verhalten im Verbrennungsrohr und ihre Absorption an geeigneten Kontakten wurden untersucht. Durch den Einsatz³²P- markierter Ausgangsverbindungen und Aktivitätsmessung des³²P sowohl durch die Wandung des Verbrennungsrohres als auch im zerkleinerten Füllungsmaterial war die laufende Bestimmung der durch die Kontaktschicht absorbierten Phosphormenge möglich. 30 verschiedene Absorptionsmittel wurden geprüft. Der Einfluß der Strömungsgeschwindigkeit des Trägergases, der Temperatur der Kontaktschicht, der Art der Verbrennung sowie der Anordnung des Verbrennungsrohres wurde untersucht. Die Absorptionsleistung der Kontakte ist stark von der Gasgeschwindigkeit abhängig.

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Investigation of absorption of the phosphorus oxides arising in the combustion of organophosphorus compounds by means of³²P-labelled substances

Summary In the pyrolysis of organophosphorus compounds in an oxygen atmosphere P oxides are formed which interfere with determination of carbon and hydrogen. Their behaviour in the combustion tube and their absorption on suitable contacts were investigated. By the use of³²P-labelled starting compounds and measuring the activity of³²P both through the wall of the combustion tube and in the comminuted filling material, continuous determination of the amount of phosphorus absorbed through the contact layer was possible. Thirty different absorption media were tested. The influence of the flow rate of the carrier gas, the temperature of the contact layer, the nature of combustion as well as the arrangement of the combustion tube was examined. The absorption efficiency of the contacts is highly dependent on the speed of the gas.

     

Über einige neue Bispirane

We have obtained four new bispirane systems in which both spiroatoms are vicinal atoms in cyclopropane or cyclobutane rings and in which the heterocyclic component has the basic structure of 1,4-dioxep-2-ene. We have shown that from two possibilities (bispiran, propellan) the general reaction leads only to a bispiran system. To the bispiran2 exhibiting the highest hyperchromism we ascribed the bispirocoplanar conformation (Fig. 1).

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Mit 3 Abbildungen     

Radiation reduction of Cr, Mo and W isopolymetalates in aqueous system

The radiation-chemical processes in aqueous solutions of dichromates, isopolymolybdates and isopolytungstates have been studied. The radiation reduction of Cr(VI) to Cr(III), Mo(VI) to Mo(V) and W(VI) to W(V) takes place. Molybdenum and tungsten blues are the products of the last two processes in acid solutions. The yields of reduction decrease significantly with the increase of pH. The mechanisms of the processes have been discussed. The photochemical reduction of Mo(VI) and W(VI) for the production of corresponding 5-valent states have been used to the study of their electron scavenging efficiencies. It has been shown that these efficiencies decrease in the order: Mo(V)>W(V)>Cr(VI)>Mo(VI)>W(VI).     

The First Reaction of Dimethoxycarbene with an Imine Moiety

The nucleophilic dimethoxycarbene (DMC; 2 ) generated by thermal decomposition of 2,5‐dihydro‐1,3,4‐oxadiazole derivative 1 in boiling toluene reacts smoothly with N‐(9H‐fluoren‐9‐ylidene)‐4‐methylbenzenesulfonamide ( 7b ) to yield carbonimidoate derivative 10 . A multi‐step reaction pathway, initiated by the attack of DMC onto the C?N bond and followed by the migration of the sulfonyl group (or via a sulfinate anion) is proposed to explain the formation of the final product. In contrast to the formal ketimine 7b , N‐benzylidene‐4‐methylbenzenesulfonamide ( 7a ), a formal aldimine, does not react with DMC under comparable conditions.     

Separation of four platinum metals by anion-exchange in hydrobromic acid medium

Distribution coefficients of Pt, Ir, Pd and Rh in the systems Dowex 1 [Br^?]?HBr plus 0.0035M bromine and Dowex 1 [Br^?]?HBr plus 2% N₂H₄·HCl, were determined with the aid of radioactive tracers by batch equilibration for the resins of nominal cross-linking 2, 4 and 8, respectively. Column experiments showed that Dowex 1X4 should be used for separations because of the favourable dynamics of the column process. Elution conditions for the quantitative separation of both trace and milligram amounts of Ir?Pt, Rh?Pt, Pd?Pt and Ir?Pd?Pt mixtures are given. Some data on the effect of temperature upon the quality of separation are also presented.     

Monitoring of the metal displacement from the recombinant mouse liver metallothionein Zn(7)-complex by capillary zone electrophoresis with electrospray MS detection

A solution of a Zn-complex of recombinant mouse MT-1 isoform (Zn(7)-MT-1) was prepared and titrated with Cd(2+) ions. A method based on the coupling of capillary zone electrophoresis (CZE) with electrospray MS detection was developed for the analysis of the stoichiometry of the species formed during the titration. The method offered the possibility of the on-line removal of up to 100 mM Tris or phosphate buffer solutions that would otherwise suppress the electrospray signal. By allowing the determination of the metal stoichiometry of the complex species present in solution the method was shown to be complementary to circular dichroism and UV-VIS spectrophotometry conventionally used for similar studies. The titration of the Zn(7)-MT complex with Cd(II) showed the sequential displacement of the Zn by Cd. The unusually high stability of the Cd(6)Zn(1)-MT species was observed which suggests a structural role of the remaining Zn(II) ion.     

Studies on the copolymerization of unsaturated 1,3-dioxane derivatives—IV. Radical copolymerization of 2-furyl-5,5-dimethyl-1,3-dioxane with maleic anhydride

The copolymerization of 2-furyl-5,5-dimethyl-1,3-dioxane with maleic anhydride in the presence of a radical catalyst yields equimolar, alternating copolymers in which the furyl units have 2,5-linkage. It has been shown that 2-furyl-5,5-dimethyl-1,3-dioxane forms a charge transfer complex with maleic anhydride. The equilibrium constant for the complex was determined by NMR spectroscopy.     

Investigation of arsenic speciation in oyster test reference material by multidimensional HPLC-ICP-MS and electrospray tandem mass spectrometry (ES-MS-MS)

Multidimensional (size-exclusion-anion-exchange-cation-exchange) liquid chromatography with ICP-MS detection was developed to produce a map of water-soluble species in an oyster test reference material. The presence of arsenobetaine, trimethyl(2-carboxyethyl)arsonium inner salt, arsenocholine, dimethylarsonic acid, tetramethylammonium ion, As(v) and two arsenosugars was demonstrated by ES-MS-MS. A previously unreported compound was isolated and identified by ES-MS-MS as 5-dimethylarsinoyl-beta-ribofuranose. Anion-exchange chromatography was optimized to produce a chromatographically pure peak of arsenobetaine (accounting for ca. 64% of all water-soluble As present) that was used to quantify this compound.