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The influence of the microstructures of different kappa-carrageenan gels on the self-diffusion behavior of poly(ethylene glycol) (PEG) has been determined by nuclear magnetic resonance (NMR) diffusometry and transmission electron microscopy (TEM). It was found that the diffusion behavior was determined mainly by the void size, which in turn was defined by the state of aggregation of the kappa-carrageenan. The kappa-carrageenan concentration was held constant at 1 w/w%, and the aggregation was controlled by the amount of potassium and/or sodium chloride and, for samples containing potassium, also by the cooling rate. Gels containing potassium formed microstructures where kappa-carrageenan strands are rather evenly distributed over the image size, while sodium gels formed dense biopolymer clusters interspersed with large openings. In a gel with small void sizes, relatively slow diffusion was found for all PEG sizes investigated. Extended studies of the self-diffusion behavior of the 634 g mol(-)(1) PEG showed that there is a strong time dependence in the measured PEG diffusion. An asymptotic lower time limit of the diffusion coefficient was found in all gels when the diffusion observation time was increased. According to the ratio, D/D(0), where D(0) is the diffusion coefficient in D(2)O and D is the diffusion coefficient in the gels, the gels could be divided into three classes: small, medium, and large voids. For quenched kappa-carrageenan solutions with salt concentrations of 20 mM K(+), 100 mM K(+), or 20 mM K(+)/200 mM Na(+) as well as slowly cooled solutions with only 20 mM K(+), D/D(0) ratios between 0.18 and 0.29 were obtained. By quenching a kappa-carrageenan solution with 100 mM K(+), the D/D(0) was 0.5, while D/D(0) ratios between 0.9 and 1 were obtained in a quenched solution with 250 mM Na(+) and slowly cooled samples with 20 mM K(+)/200 mM Na(+) or 250 mM Na(+).

Liquid chromatography coupled to mass spectrometry (LC-MS) is a major platform in metabolic profiling but has not yet been comprehensively assessed as to its repeatability and reproducibility across multiple spectrometers and laboratories. Here we report results of a large interlaboratory reproducibility study of ultra performance (UP) LC-MS of human urine. A total of 14 stable isotope labeled standard compounds were spiked into a pooled human urine sample, which was subject to a 2- to 16-fold dilution series and run by UPLC coupled to time-of-flight MS at three different laboratories all using the same platform. In each lab, identical samples were run in two phases, separated by at least 1 week, to assess between-day reproducibility. Overall, platform reproducibility was good with median mass accuracies below 12 ppm, median retention time drifts of less than 0.73 s and coefficients of variation of intensity of less than 18% across laboratories and ionization modes. We found that the intensity response was highly linear within each run, with a median R(2) of 0.95 and 0.93 in positive and negative ionization modes. Between-day reproducibility was also high with a mean R(2) of 0.93 for a linear relationship between the intensities of ions recorded in the two phases across the laboratories and modes. Most importantly, between-lab reproducibility was excellent with median R(2) values of 0.96 and 0.98 for positive and negative ionization modes, respectively, across all pairs of laboratories. Interestingly, the three laboratories observed different amounts of adduct formation, but this did not appear to be related to reproducibility observed in each laboratory. These studies show that UPLC-MS is fit for the purpose of targeted urinary metabolite analysis but that care must be taken to optimize laboratory systems for quantitative detection due to variable adduct formation over many compound classes.

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Die Titelverbindung [Ni(dppe)2] (dppe  Ph2PCH2CH2PPh2) kristallisiert in der monoklinen Raumgruppe P21/n mit den Gitterkonstanten a = 983,2(2), b = 2119,2(3), c = 2145,1(4) pm, β = 91,97(1)° und vier Molekülen pro Elementarzelle. Die Struktur wurde auf der Grundlage von 2779 beobachteten symmetrieunabhängigen Reflexintensitäten nach der Schweratommethode gelöst und bis zu einem R‐Wert von 0,063 (RW = 0,052) verfeinert. Das Ni‐Atom als Spirozentrum ist verzerrt tetraedrisch von den vier P‐Atomen der beiden zweizähnigen Chelatliganden umgeben. Die sehr ähnlichen Ni‐P‐Abstände weisen einen Mittelwert von 216(1) pm auf. Der aus der Molekülstruktur von [Ni(dppe)2] berechnete mittlere Öffnungswinkel für den Tolman‐Kegel von dppe beträgt 129,8°.

Durch Reaktion von Cl2PCH2CH2PCl2 mit Bu1MgCl wird ButClPCH2CH2PClBut erhalten, das entweder zu ButH(O)PCH2CH2P(O)HBut hydrolysiert oder zu ButHPCH2CH2PHBut reduziert wird. Dieses PHosphin ergibt mit Schwefel bzw. Selen ButH(E)PCH2CH2P(E) HBut (E = S, Se). Ph2PCH2CH2Cl und LiPHBut setzen sich zu Ph2PCH2CH2PHBt um, das zu Ph2(E)PCH2CH2P(E)HBt (E = O, S, Se) oxidiert wird, wobei primär die PH2P‐Gruppe reagiert. Die dargestellten Verbindungen werden mit Hilfe ihrer IR‐, 1H‐ und 31P‐Spektren charakterisiert.

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