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281.
Using velocity map ion imaging technique, the photodissociation of n-C4H9Br in the wavelength range 231–267 nm was studied. The results and our ab initio calculations indicated that the absorption of n-C4H9Br in the investigated region originated from the excitations to the lowest three repulsive states, as assigned as 1A″, 2A′ and 3A′ in Cs symmetry. Dissociations occurred on the PES surfaces of the three states, terminating in C4H9+Br (2P3/2) or C4H9 + Br* (2P1/2) as two channels, and being impacted by an avoided crossing between the PES surfaces of the 2A′ and 3A′ states. The transition dipole to the 1A″ state was perpendicular to the symmetry plane, so perpendicular to the C–Br bond. The transitions to the 3A′ state was polarized parallel to the symmetry plane, and also parallel to the C–Br bond. While the transition dipole to the 2A′ state was in the symmetry plane, but formed an angle of about 53.1° with the C–Br bond. We have also determined the avoided crossing probabilities, which affected the relative fractions of the individual pathways, for the photolysis of n-C4H9Br near 234 nm and 267 nm. 相似文献
282.
In this work, two kinds of chelating resin, bis(2-aminoethylthio)methylated resin (BAETM) and γ-aminobutyrohydroxamate resin (γ-ABHX) were synthesized. Of these, the former has a hydrophobic skeleton, and the latter a hydrophilic skeleton. The functionalities of each were 0.91 and 2.21 mmol g−1, respectively. The chelating behavior of these resins towards vanadium, molybdenum and tungsten as a function of pH was studied. To perform trace metals analysis in complex matrices, a hyphenated method-chelation ion chromatography (CIC) coupled on-line detection with inductively coupled plasma mass spectrometry (ICP-MS) was developed. With a BAETM resin column (5×0.4 cm i.d.) as the separator, a sample volume of 20 μl, nitric acid (pH 1.5) as the eluent and a flow rate of 1 ml min−1, the detection limits for the determination of vanadium, molybdenum and tungsten were lower than 0.05 ng ml−1and the linear ranges were up to 100 ng ml−1 for each element. By increasing the injected sample volume to 250 μl, the resin concentrator improved the detection limit to 0.01 ng ml−1. For the determination of these elements (5 ng ml−1 for each) spiked in artificial sea water samples, γ-ABHX resin column (3×0.6 cm i.d.) demonstrated well resolved peak separation between the analytes and the matrix elements—calcium and magnesium, by using sodium nitrate (10 ml, 10−4 M) as the eliminator. 相似文献
283.
An extract of crystal violet-tetrachloroferrate(III) in nitrobenzene was used to prepare a tetrachloroferrate(III)-selective liquid membrane electrode with a poly(vinyl chloride) support. The optimal conditions to determine 2.5 × 10–5 – 5.0 × 10–2
M iron(III) as tetrachloroferrate(III) (anionic slope 56 mV/decade, detection limit 7.9 × 10–6
M) were found to be 4.0–5.5.M total chloride in 0.75–1.5M hydrochloric acid. The electrode was reliably applied to determine iron in human blood, haematite and mineralized vitamin syrup by direct potentiometry, standard and sample additions as well as standard subtraction techniques. 相似文献
284.
Johannes Smid 《Journal of polymer science. Part A, Polymer chemistry》2004,42(15):3655-3667
The discovery and implications of the existence of two kinds of ion pairs in solutions of carbanion salts is described. Also discussed are the factors controlling tight–loose ion pair equilibrium: the nature of the carbanion and its counterion, temperature, pressure, solvent, and cation‐complexing additives. A few examples are presented of the effect of these ionic species on the mechanisms of anionic polymerization and proton transfer. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3655–3667, 2004 相似文献
285.
Marcos J Pascual JA de la Torre X Segura J 《Journal of mass spectrometry : JMS》2002,37(10):1059-1073
A fast and sensitive method for the comprehensive screening of anabolic agents and other banned doping substances using gas chromatography/tandem mass spectrometry (GC/MS/MS) with an external ionization ion trap mass spectrometer is presented. The method takes advantage of the resolving power of MS/MS to eliminate background interferences, thus speeding up the chromatographic analysis. For each compound, different fragmentation reactions were studied and their collision energies optimized to obtain the best sensitivity in terms of their signal-to-noise ratio (S/N). A dramatic reduction in overall analysis time was achieved compared with other common approaches. More than 50 substances could finally be monitored in less than 7.4 min with detection limits (S/N >3) lower than 0.5 ng ml(-1) for most of the compounds with special sensitivity requirements according to the International Olympic Committee (IOC). A validation procedure for qualitative analysis was performed. The selectivity of the method showed that no interfering peaks were observed at the retention time of the analytes. Good intermediate precision, below 25% for most of the compounds, and robustness were observed. The optimized method was successfully applied to analyse more than 100 real human urine samples with optimum sensitivity and specificity rates. 相似文献
286.
研究了硫酸铵存在下硫氰酸铵-罗丹明B-H2O的液-固体系浮选分离铜(Ⅱ)的行为及其与常见离子分离的条件.结果表明,当(NH4)2SO4用量为1.0 g,0.1 mol·L-1硫氰酸铵溶液1.5 mL和0.001 mol·L-1罗丹明B溶液2.0 mL时,铜(Ⅱ)以不溶于水的三元离子缔合物(RhB)2[Cu(SCN)4]形式在液-固两相界面定量浮选析出,而Cdd2、Mn2+、Co2+、Ni2+、Al3+等离子在此条件下不被浮选,实现了铜(Ⅱ)与这些离子的定量分离,对合成水样中微量铜(Ⅱ)进行的定量浮选分离测定,浮选富集的平均回收率达101.4%. 相似文献
287.
M. Domínguez-Pérez J. Jiménez de Llano L. Segade C. Franjo O. Cabeza 《Journal of Thermal Analysis and Calorimetry》2005,79(2):289-293
Summary This paper reports excess molar enthalpies of the binary systems hexane+ethyl benzene, hexane+o-xylene, hexane+m-xylene and hexane+p-xylene at 298.15 K and atmospheric pressure, over the whole composition range. The data was measured directly using a Calvet microcalorimeter. The excess magnitude was correlated to a Redlich-Kister type equation for each mixture. Also, we will discuss the results for the four mixtures studied here and by comparison with the same binary systems but containing propyl propanoate as first component. Finally, we will correlate our results with the Nitta-Chao and the three UNIFAC theoretical approximations. 相似文献
288.
J. Rodriguez-Añón J. Prouupin M. González-Añón L. Núñez-Regueira 《Journal of Thermal Analysis and Calorimetry》1998,52(3):1005-1012
The heating values of municipal solid waste generated in three towns with a population of less than 50 000, situated in Galicia
(Spain), were measured with a static bomb calorimeter. Samples of raw refuse were burnt either as received or after sorting
of the different combustible components. A study was made of samples from controlled and uncontrolled landfills.
The calorific values were compared with those corresponding to a commercial residual derived fuel in order to study the possibility
of using municipal solid waste as a source of recovered energy.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
289.
The apparent molal volume and adiabatic compressibilities of some transition metal (Mn2+, Co2+ Ni2+, Cu2+, Zn2+, and Cd2+) sulfates have been determined at 25°C. Values of
to 11.4 cm3-mole–1 and
to 31.3 × 10–4cm3-mole–1-bar–1 at 1 atm were found for the formation of the transition metal sulfate ion pairs. These results are in good agreement with the values obtained from the high-pressure conductance measurements of Fisher et al., Shimizu et al., and Taniguchi et al. The volume and compressibility data indicate that 3.1±0.7 water molecules are lost when transition metals form ion pairs with SO
4
2–
. The fractions of inner-sphere ion pairs (20%) estimated in this study are in good agreement with the values obtained from ultrasonic measurements. 相似文献
290.
纤维素基磁性聚偕胺肟树脂的研究——循环吸溴中吸附与还原能力的变化 总被引:3,自引:0,他引:3
研究了酸式纤维素基磁性聚偕胺肟树脂(AMAO)在循环吸溴过程中吸附容量和还原能力的变化,发现原树脂的吸溴初速和溴的还原率比再生树脂高一倍以上,但第一次和第二次再生树脂的吸附速度和还原效率几乎相同,暗示着树脂吸溴后基本结构已发生了彻底的变化.树脂在循环使用时吸溴容量变化不大而溴的还原量却显著降低,表明AMAO作为吸溴剂有较高的实用价值. 相似文献