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41.
Henry Holmstrand Maria Unger Daniel Carrizo Per Andersson Örjan Gustafsson 《Rapid communications in mass spectrometry : RCM》2010,24(14):2135-2142
The bromine isotope composition is potentially diagnostic in both degradation monitoring and source apportionment of organobromines in the environment. A method for compound‐specific bromine isotope analysis (δ81Br) based on gas chromatography multiple collector inductively coupled plasma mass spectrometry (GC/ICPMS) was developed for common brominated diaromatic compounds. Brominated diphenyl ethers (BDEs) in Bromkal 70‐5DE, a technical flame‐retardant mixture containing mainly BDEs #47, #99 and #100, were used as test substances, with standard bracketing for the samples achieved through co‐injected monobromobenzene (MBB) with a known δ81Br of ?0.39‰ vs. Standard Mean Ocean Bromine (SMOBr). Three different heated transfer lines were constructed and tested to achieve efficient conduction of the BDEs from the gas chromatograph to the ICPMS instrument. The MBB was analyzed with a precision of 0.4‰ (1 s, n = 18). The precision for BDEs was 1.4–1.8‰ (1 s, n = 10–12 depending on the congener). The lower precision for the BDEs than for MBB may reflect the heat required to prevent condensation of the analytes in ICP torch assembly. The use of an internal standard of similar chemical structure to the analytes alleviates this problem, as illustrated by a difference of 0.3 ± 0.7‰ (1 s, n = 6) between the δ81Br values of co‐injected methoxy BDE‐47 and BDE‐47 extracted from whale blubber. Improvements in precision and accuracy may be achieved by the use of a more efficient heating of the torch assembly in conjunction with a set of internal standards that match the target compounds. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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In this article, a new semivectorial finite-difference method is presented. By comparing the results obtained by the new approach
with a vectorial method, it is shown that the accuracy is still very high with costs reduced by a factor of two.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
44.
Conny Unger Olga Kofanova Kate Sokolowska Daniel Lehmann Fay Betsou 《Electrophoresis》2015,36(17):2072-2081
The analytical and clinical validity of analyses of RNA samples destined for clinical diagnosis and therapeutic management is directly impacted by RNA quality. RNA is affected by heat, enzymatic degradation, and Ultraviolet (UV) light. RNA from three eukaryotic cell lines was degraded by heat, RNase, or UV light. RNA integrity values obtained with the benchmark Agilent Bioanalyzer 2100 system were compared with those from the more recent QIAxcel Advanced system. The application of this novel method has allowed us to unravel differences between RNA biophysical and biochemical degradation modes. Agilent RNA integrity number (RIN) and QIAxcel RIS were comparable in heat‐degraded and RNase III‐degraded RNA. Agilent RIN and QIAxcel RIS were comparable at a RIN decision level of 7 in UV‐degraded RNA but not overall. The QIAxcel RIS method was more precise than Agilent RIN for RIN<8, while the inverse was true for RIN≥8. Greater degradation of mRNA and rRNA in UV‐damaged samples hampered the Agilent RIN calculation algorithm. Overall, RIS was more robust than RIN for assessing RNA integrity. The ΔΔCt‐values for heat‐ and UV‐degraded RNA samples showed slightly higher correlation with RIS than with RIN. RNA integrity can be used to categorize RNA samples for suitability for downstream gene expression analyses, independently of the RNA degradation mechanism. The new method QIAxcel is more robust and therefore allows more accurate categorization of compromised RNA samples. 相似文献
45.
Dietrich PM Horlacher T Girard-Lauriault PL Gross T Lippitz A Min H Wirth T Castelli R Seeberger PH Unger WE 《Langmuir : the ACS journal of surfaces and colloids》2011,27(8):4808-4815
Carbohydrate films on gold based on dimannoside thiols (DMT) were prepared, and a complementary surface chemical analysis was performed in detail by X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), near-edge X-ray absorption fine structure (NEXAFS), FT-IR, and contact angle measurements in order to verify formation of ω-carbohydrate-functionalized alkylthiol films. XPS (C 1s, O 1s, and S 2p) reveals information on carbohydrate specific alkoxy (C-O) and acetal moieties (O-C-O) as well as thiolate species attached to gold. Angle-resolved synchrotron XPS was used for chemical speciation at ultimate surface sensitivity. Angle-resolved XPS analysis suggests the presence of an excess top layer composed of unbound sulfur components combined with alkyl moieties. Further support for DMT attachment on Au is given by ToF-SIMS and FT-IR analysis. Carbon and oxygen K-edge NEXAFS spectra were interpreted by applying the building block model supported by comparison to data of 1-undecanethiol, poly(vinyl alcohol), and polyoxymethylene. No linear dichroism effect was observed in the angle-resolved C K-edge NEXAFS. 相似文献
46.
Unger EL Morandeira A Persson M Zietz B Ripaud E Leriche P Roncali J Hagfeldt A Boschloo G 《Physical chemistry chemical physics : PCCP》2011,13(45):20172-20177
The hole transporting medium in solid-state dye-sensitized solar cells can be utilized to harvest sunlight. Herein we demonstrate that a triphenylamine-based dye, used as hole-transporting medium, contributes to the photocurrent in a squaraine-sensitized solid-state dye-sensitized solar cell. Steady-state photoluminescence measurements have been used to distinguish between electron transfer and energy transfer processes leading to energy conversion upon light absorption in the hole-transporting dye. 相似文献
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MnBi films were prepared by annealing Bi-Mn composite films. The grain size of the MnBi films was strongly influenced by the
temperatureT
s
of the film substrate during evaporation of Bi and Mn. For 55-nm-thick films, the numberN of MnBi grains per mm2 decreased from 4×106 per mm2 forT
s
=+90°C to 1 per mm2 forT
s
=−40°C. The diameters of the largest grains observed were about 5 mm. For interpretation of this result, the formation process
of MnBi films was observed magneto-optically and electronmicroscopically. It was found thatN was determined by the structure of Bi in the Bi-Mn composite films and that this strongly depended onT
s
. 相似文献