Determination of surfactants in river water applying XAD-4/RP-18-extraction

Anionic, cationic and nonionic surfactants have been extracted simultaneously from river water using a combination of XAD-4 coupled to reversed phase-18 (RP-18) material. After desorption the surfactants have been separated into the individual classes and determined by HPLC with post-column derivatization and florescence detection. The results obtained are compared to the surfactant concentrations determined utilizing the cumulative parameter method.This article is part of the envisaged Ph.D. thesis of Andrea Kreißelmeier at the University of Duisburg     

Storage stability of polycyclic aromatic hydrocarbons collected from ambient air using solid supports

Summary During experiments using paired high-volume sampling of ambient air to collect polycyclic aromatic hydrocarbons (PAH's) on teflon filters backed up by a polyurethane-foam plug (PUF) we had also the opportunity to study the storage stability of these PAH's. Teflon filters and PUF were stored separately in closed vessels in the dark at room temperature for periods ranging from 35 to 118 days before extraction, clean-up and analysis by gas chromatography. Compared to the samples analyzed directly after the end of collection, all PAH's ranging in volatility from fluoranthene/pyrene to coronene were recovered in essentially the same amounts from stored samples, both from those collected during summer (range 2.3–0.1 ng/m³) and winter time (range 9.0–0.7 ng/m³). Thus, storage of these solid supports seems to be a reliable tool to preserve the integrity of collected air samples, even for a longer period of time.     

Comparison of passive and active sampling methods for the determination of nitrogen dioxide in urban air

Three different methods for sampling and determination of nitrogen dioxide in urban air are compared: an NO/NO_x-monitor and an active (pumped) and a passive sampling method. For the latter two methods, sodium iodide is used as absorbent. For weekly averages the results from the passive sampler are within 10–20% of the results for the two other methods in the concentration range 15–30 μg NO₂/m³. The detection limit for the passive sampler is 1 μg NO₂/m³ (7 days), the precision is 5% and the accuracy is estimated to 20%. The active iodide method agrees very well with the NO/NO_x-monitor. Compared on 24 h basis for a period of 3 months, covering a concentration range of 5–45 μg NO₂/m³, the deviation between the two methods is within 5%, and the absorption capacity of the iodide reagent is excellent as the breakthrough is below 1%.     

Comparison of passive and active sampling methods for the determination of nitrogen dioxide in urban air

Three different methods for sampling and determination of nitrogen dioxide in urban air are compared: an NO/NO_x-monitor and an active (pumped) and a passive sampling method. For the latter two methods, sodium iodide is used as absorbent. For weekly averages the results from the passive sampler are within 10–20% of the results for the two other methods in the concentration range 15–30 μg NO₂/m³. The detection limit for the passive sampler is 1 μg NO₂/m³ (7 days), the precision is 5% and the accuracy is estimated to 20%. The active iodide method agrees very well with the NO/NO_x-monitor. Compared on 24 h basis for a period of 3 months, covering a concentration range of 5–45 μg NO₂/m³, the deviation between the two methods is within 5%, and the absorption capacity of the iodide reagent is excellent as the breakthrough is below 1%. Received: 3 December 1996 / Revised: 11 March 1997 / Accepted: 15 March 1997     

Photocatalyzed thiol–alkene coupling: Mechanistic study and polymer synthesis

Due to the “click” chemistry characteristics of the thiol–ene reaction, these transformations have been gaining an increasing amount of attention in current chemical research. The high efficiency and selectivity of these transformations have been useful for many areas of study, from small molecule organic synthesis, to polymer synthesis and functionalization, to bio‐conjugation reactions. In this work, a study of a novel method of photochemical thiol–ene reactions using alkyl halides and an tris[2‐phenylpyridinato‐C2,N]iridium(III) (Ir(ppy)₃) photocatalyst is investigated. This process is shown to progress rapidly and has the benefit of low catalyst and initiator concentrations relative to reagents as well as mild conditions associated with photochemical processes. To understand the mechanism of this process, catalyst and initiator concentrations and other reaction conditions are varied. To demonstrate the utility of this process, a step‐growth thiol–ene polymer is synthesized using dithiol and diene monomers and a crosslinked polymer network is synthesized as well. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1931–1937     

Frobenius Quasigroups and Regular Polygons

In terms of regular n-gons a left distributive quasigroup operation is defined on the complex plane. This operation can be expressed by means of a semidirect product G of the translation group (which is sharply transitive on the points of the plane and hence may be identified with the plane) by a finite cyclic group of rotations of order n. That observation makes possible a wide generalization of this geometric quasigroup construction. The connection in general between algebraic properties of the quasigroup and various properties of the group G is discussed, in particular it is studied what the consequences for the quasigroup Q are if G is interpreted as a topological group or an algebraic group.     

A new reference material for radionuclides in the mussel sample from the Mediterranean Sea (IAEA-437)

A new Reference Material (RM) for radionuclides in mussel (Mytilus galloprovincialis) from the Mediterranean Sea (IAEA-437) is described and the results of the certification process are presented. Four radionuclides (⁴⁰K, ²³⁴U, ²³⁸U, and ^239+240Pu) have been certified, and information values on massic activities with 95% confidence intervals are given for nine radionuclides (¹³⁷Cs, ²¹⁰Pb(²¹⁰Po), ²²⁶Ra, ²²⁸Ra, ²²⁸Th, ²³⁰Th, ²³²Th, ²³⁵U, and ²⁴¹Am). Results for less frequently reported radionuclides (⁹⁰Sr, ¹²⁹I, ²³⁸Pu, ²³⁹Pu, and ²⁴⁰Pu) are also reported. The RM can be used for quality assurance/quality control of the analysis of radionuclides in mussel samples, for the development and validation of analytical methods and for training purposes. The material is available in 200 g units.     

Feasibility studies for the preparation and certification of reference materials Part II: mineral oil contaminated waste materials

The 2-year international joint project HYCREF (Contract-No. G6RD-CT-2002-00854), funded by the European Commission in the 5th Framework programme, aimed to develop methods to prepare homogenous and stable water-, soil- and waste reference materials contaminated with mineral oil hydrocarbons and to test certify the mineral oil content by gas chromatographic methods. As mineral oil products are important sources for environmental contaminations, appropriate reference materials certified by using the new gas chromatographic methods (soil: ISO/FDIS 16703, waste: prEN 14039 and KW/04, water: ISO 9377-2) are highly needed. Additional to the HYCREF-results presented in part I–mineral contaminated soils–this second paper gives an overview of the feasibility study for the preparation and test certification of three waste reference materials (offshore marine sediment, building material and industrial waste). The following specifications, which had been defined in the project work plan, were reached successfully: uncertainty of the mineral oil content resulting from the certification exercise ≤5% and a between-bottle inhomogeneity of ≤3%. All three materials have been evaluated for long- and short term stability. They contain different levels and types of mineral oil and cover the full application range of ISO/FDIS 16703 and prEN 14039 (100–10,000 mg/kg). The expanded uncertainties U _cert of the three materials are about 6%. In this way, they are comparable to ERM^®-CC015a (U _cert=7.1%, mineral oil in a river sediment) and are suited to close the present gap of commercially available CRM for mineral oil determination in waste.     

Speciation studies for arsenic and mercury-applications and prospects

Methods are described for the speciation of arsenic and mercury in biological and environmental materials. For arsenic various methods were developed to distinguish between more or less toxic arsenic compounds and non-toxic compounds. For the determination of methylmercury a modification of the Westöö procedure was applied for higher contents as well as anion exchange down to levels below 0.1 g/kg in solids and below 0.1 ng/1 in liquids.