HPLC separation and quantification of anionic surfactants using an automated on-line ion pair extraction system

Summary Aliphatic anionic surfactants, like alkylsulfonates, alkyl sulfates, -sulfo alkanoic acids and their esters, were separated with respect to their alkyl chain length by high performance liquid chromatography (HPLC) using reversed phase (RP) columns. For sensitive and specific detection of these classes of compounds the HPLC separation was combined with a post-column ion-pair extraction system. The limit of detection is in the range of 3–30 ng. Previously reported detection systems of this kind were modified by changing the inner set-up of the phase separator and the extraction capillary and integrating a purge function, which led to a higher system stability and made automatization possible. In order to optimize the experimental set-up, the influence of the reagent concentration as well as different sizes and materials of the extraction capillary were evaluated. The calibration curve of surfactant concentrations versus fluorescence emission is discussed for sodium decylsulfonate. Since both the electrolyte concentration and the percentage of organic solvents in the mobile phase may adversely affect the detection system, different eluent compositions were tested.This article is part of the planned dissertation of Markus Schoester at the Mathematical Natural Science Faculty of the University of Düsseldorf     

A new chiral Rh(II) catalyst for enantioselective [2 + 1]-cycloaddition. mechanistic implications and applications

A novel chiral Rh(II) catalyst (1) is introduced for the [2 + 1]-cycloaddition of ethyl diazoacetate to terminal acetylenes and olefins with high enantioselectivity. The catalyst 1 consists of one acetate bridging group and three mono-N-triflyldiphenylimidazoline-2-one bidentate ligands (DPTI) spanning the Rh(II)-Rh(II) metallic center in a structure that was determined by single-crystal X-ray diffraction analysis. A rational mechanism is advanced that provides a straightforward explanation for the enantioselectivity and absolute stereochemical course of the [2 + 1]-cycloaddition reactions. A key element in this explanation is the cleavage of one of the Rh-O bonds of the bridging acetate group in the intermediate Rh-carbene complex to form a new pentacoordinate Rh carbene complex (formally 1.5 valent Rh) that can undergo [2 + 2]-cycloaddition with the C-C pi-bond of the acetylenic or olefinic substrate. Reductive elimination of the resulting adduct affords the cyclopropene or cyclopropane product. The C2-symmetry of the two DPTI ligands orthogonal to the bridging acetate also contributes to the high observed enantioselectivity and mechanistic clarity. The catalyst 1, which functions effectively at 0.5 mol %, can be recovered efficiently for reuse. Its ready availability, robustness, and effectiveness suggest it as a useful addition to the list of practical chiral Rh(II) catalysts for synthesis.     

A certified reference material for radionuclides in the water sample from Irish Sea (IAEA-443)

A new certified reference material (CRM) for radionuclides in sea water from the Irish sea (IAEA-443) is described and the results of the certification process are presented. Ten radionuclides (³H, ⁴⁰K, ⁹⁰Sr, ¹³⁷Cs, ²³⁴U, ²³⁵U, ²³⁸U, ²³⁸Pu, ^239+240Pu and ²⁴¹Am) have been certified, and information values on massic activities with 95% confidence intervals are given for four radionuclides (²³⁰Th, ²³²Th, ²³⁹Pu and ²⁴⁰Pu). Results for less frequently reported radionuclides (⁹⁹Tc, ²²⁸Th, ²³⁷Np and ²⁴¹Pu) are also reported. The CRM can be used for quality assurance/quality control of the analysis of radionuclides in water samples, for the development and validation of analytical methods and for training purposes. The material is available in 5 L units from IAEA (http://nucleus.iaea.org/rpst/index.htm).     

Maritime inventory routing with multiple products: A case study from the cement industry

This paper considers a maritime inventory routing problem faced by a major cement producer. A heterogeneous fleet of bulk ships transport multiple non-mixable cement products from producing factories to regional silo stations along the coast of Norway. Inventory constraints are present both at the factories and the silos, and there are upper and lower limits for all inventories. The ship fleet capacity is limited, and in peak periods the demand for cement products at the silos exceeds the fleet capacity. In addition, constraints regarding the capacity of the ships’ cargo holds, the depth of the ports and the fact that different cement products cannot be mixed must be taken into consideration. A construction heuristic embedded in a genetic algorithmic framework is developed. The approach adopted is used to solve real instances of the problem within reasonable solution time and with good quality solutions.     

Determination of phosphate species in nutrient solutions and phosphorus in plant material as phosphovanadomolybdic acid by flow injection analysis

A flow-injection spectrophotometric method for the determination of orthophosphate is described. The signal from the yellow phosphovanadomolybdic acid complex is recorded at 400 nm. The detection limit is 0.1 mg P 1^?1 (as orthophosphate), the calibration graph is linear up to 30 mg P 1^?1 and up to 240 samples can be analysed per hour. The method is used in the determination of phosphorus in digested plant material, and is also applicable for separating free orthophosphate from acid-labile aluminium phosphate colloids in nutrient solutions.     

Automorphism groups of free geometries revisited

The number of types of free constructions introduced into geometry has increased steadily since the birth (2) of the free projective planes in 1943. The present paper is a follow up of (3) which introduces free geometries in terms ofsimple extensions. This point of view embeds a family of such constructions, here called the freelocally affine planes, into the discipline ofpartial order with noticeable technical simplifications as a consequence.Dedicated to Professor Helmut Mäurer on the occasion of his sixtieth birthday