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Hybrid linear analysis (HLA), as a recent factor-based multivariate calibration technique, was applied for the spectrophotometric determination of ternary mixtures of pseudoephedrine hydrochloride (PSU), dextromethorphan hydrobromide (DXT), and sodium benzoate (BNZ). The utilized HLA was assisted by a wavelength selection procedure which was based on the calculation of the net analyte signal (NAS) regression plot in any considered wavelengths window for each test sample, in addition to a moving window strategy for searching the region with maximum linearity of NAS regression plot (minimum error indicator (EI)). HLA was applied because it was simpler to adapt to the NAS regression plot methodology, and also used less factors than partial least squares (PLS). An orthogonal array design was applied for formation of calibration and prediction sets in the concentration ranges 0-7500 μmol L−1 for PSU, 0-300 μmol L−1 for DXT, and 0-1400 μmol L−1 for BNZ. The method had the ability to select wavelength regions that minimize the effect of non-linearity of the spectral data, in addition to that of non-modeled interferences. The application of the selected wavelength regions improved the obtained relative standard error of predictions for PSU, DXT, and BNZ, respectively, from 5.24, 8.67, and 5.48% to 2.19, 5.21, and 3.62% (using lower number of factors). To check the ability of the proposed method in selection of linear regions of spectra, a test for detecting non-linear regions of spectral data in multivariate spectroscopic assays was also described. Additives in the commercial syrup samples did not interfere with their determinations. The method was successfully applied for the determination of pseudoephedrine HCl, dextromethorphan HBr, and sodium benzoate in cough suppressant syrup samples. 相似文献
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Ramesh Naik 《合成通讯》2013,43(10):1723-1726
Dimethylsulfoxide (DMSO) oxidizes benzyl ethers into corresponding benzaldehydes at 110°C; the reaction is accelerated by 49% aq. HBr. The conditions work well for different aryl‐substituted benzyl ethers. This protocol is inert toward dialkyl ethers. 相似文献
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An efficient and mild method for tetrahydropyranylation of alcohols and their detetrahydropranylation using NH4Cl is described. This protocol provides a useful alternative tetrahydropyranylation of alcohols and their deprotection at different pH. 相似文献
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Various cycloalkanes and straight‐chain alkanes were efficiently brominated with an aqueous HBr‐H2O2 system. This oxidative brominating process was promoted by catalysis and irradiation with light. The cycloalkanes were converted to the corresponding bromo‐cycloalkanes in moderate yields and the straight‐chain alkanes produced dominantly secondary bromides. This simple but effective bromination method of alkanes is characterized by high atom efficiency, inexpensive reagents and the absence of organic waste, which make it a good alternative to the existing method for C? H activation through bromination. 相似文献
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HBr分子的爱因斯坦自发辐射系数的计算 总被引:1,自引:0,他引:1
本文从第一性原理出发,计算了HBr分子v≤7,J≤14,Δv=1,R,P支谱线的爱因斯坦自发辐射系数A^v‘J’v^nJ^n。测量了HBr红外发射的振转谱线强度,证实由理论计算获得的A^vJ’V^nJ^n系数是可靠的。 相似文献
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The reactions between OH radicals and hydrogen halides (HCl, HBr, HI) have been studied between 298 and 460 K by using a discharge flow-electron paramagnetic resonance technique. The rate constants were found to be kHCl(298 K) = (7.9 ± 1.3) × 10−13 cm3 molecule−1 s−1 with a weak positive temperature dependence, kHBr (298-460 K) = (1.04 ± 0.2) × 10−11 cm3 molecule−1 s−1, and kHI(298 K) = (3.0 ± 0.3) × 10−11 cm3 molecule−1 s−1, respectively. The homogeneous nature of these reactions has been experimentally tested. 相似文献
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Edit Farkas Gergely Kovács Krisztina Imrik István Szilágyi Sándor Dóbé Ferenc Márta 《Reaction Kinetics and Catalysis Letters》2004,83(2):315-320
The discharge flow method with laser induced fluorescence detection of CH3O was applied to determine the rate constant, k
1, for the reaction CH3O + HBr → products (1) k
1 (298 K) = (8.41 ± 0.80(1σ)) 1011 cm3 mol-1 s-1. The unusually large k
1 value was explained by the polar nature of the transition state of the reaction.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
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Gertrud Bartelmus und Reinhold Ketterer 《Fresenius' Journal of Analytical Chemistry》1977,286(3-4):161-190
Zusammenfassung Es werden Methoden und Apparaturen zur qualitativen und quantitativen Bestimmung von Äthergruppen in Cellulosederivaten mit einer oder mehreren Alkoxyl- und Hydroxyalkylgruppen (C1-nC4) beschrieben. Die Ätherspaltung erfolgt im allgemeinen mit Jodwasserstoffsäure und in Sonderfällen mit Bromwasserstoffsäure. Als Reaktionsprodukte entstehen Monojodalkane und Alkene oder Monobromalkane und Dibromalkane. Diese werden der gas-chromatographischen Trennung unterworfen, über die Retentionszeit identifiziert und durch Titration oder über das Gas-Chromatogramm quantitativ bestimmt.
Analysis of cellulose ether groups
A report is given on methods and apparatus for the qualitative and quantitative determination of ether groups in cellulose derivatives with one or more alkoxyl and hydroxyalkyl groups (C1-nC4). Ether splitting generally takes place with hydriodic acid and in special cases with hydrobromic acid. The resulting reaction products are monoiodoalkanes and alkenes or monobromoalkanes and dibromoalkanes, which are subjected to gas chromatographic separation and identified via the retention time and quantitatively evaluated by titration or via the gas chromatogram.相似文献
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A combination of HBr and trans-3,5-dihydroperoxy-3,5-dimethyl-1,2-dioxolane as anew and powerful oxidant was found effective for facile brotnination of different aromatic compounds at room temperature in water as a green solvent.Mild reaction conditions,high selectivity and yield,high reaction rate and non-toxicity are some of the major advantages of this synthetic protocol. 相似文献