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971.
Summary A capillary electrophoretic method has been developed for the determination of the main product as well as of by-products in technical samples of substituted pyrimidines. Both zone electrophoresis and micellar electrokinetic chromatography have been used for the separation employing electrolytes consisting of borate buffers (pH 9 to 9.4) with or without sodium dodecylsulfate. Optimization of separation selectivity could be achieved by addition of up to 20% 2-propanol or methanol to the carrier electrolyte. Quantification by internal standards resulted in relative standard deviations between 0.2 and 0.8%. By-products could be analyzed down to levels of 0.1% in technical samples.
Analyse von Pyrimidinderivaten mitteles Kapillarelektrophorese
Zusammenfassung Für die Bestimmung von Haupt- und Nebensubstanzen in technischen Proben von substituierten Pyrimidinen wurde ein kapillarelektrophoretisches Analysenverfahren entwickelt. Sowohl Zonenelektrophorese als auch mizellare elektrokinetische Chromatographie mit Trägerelektrolyten bestehend aus Boratpuffern (pH 9 bis 9.4) mit oder ohne Natriumdodecylsulfat wurden für die Trennung eingesetzt. Eine Optimierung der Trennselektivität war durch die Zugabe von bis zu 20% 2-Propanol oder Methanol zum Trägerelektrolyten möglich. Quantifizierung mittels interner Standards ergab relative Standardabweichungen zwischen 0.2 und 0.8%. Nebenprodukte konnten in technischen Proben bis zu Gehalten von 0.1% analysiert werden.相似文献
972.
Colombini MP Carmignani A Modugno F Frezzato F Olchini A Brecoulaki H Vassilopoulou V Karkanas P 《Talanta》2004,63(4):839-848
The materials used in the decoration of three painted astragaloi (knucklebones) from the Koroneia cave (Greece) were investigated by means of sequential application of non-destructive and destructive techniques: optical microscopy, environmental scanning electron microscopy coupled with X-ray microanalysis (ESEM-EDX), Fourier transform infrared spectroscopy (FTIR) with micro-attenuated total reflection (μ-ATR) technique, high performance liquid chromatography (HPLC) coupled with UV-fluorescence and gas chromatography-mass spectrometry (GC-MS) were used.The main results highlighted that the three astragaloi were prepared with a ground of ochre or iron clay and painted with a proteinaceous matter such as binder egg tempera. Both FTIR and GC-MS agree in the detection of lipids that can be related to egg. Organic dyestuffs identified as madder lake and shellfish purple were used together with inorganic pigments. 相似文献
973.
974.
超临界流体在有机合成中的应用 总被引:9,自引:0,他引:9
超临界化学反应是一种新型的反应体系,本文对超临界流体在有机合成反应中应用的最新进展进行了综述。 相似文献
975.
4-hydroxy-4 ‘-nitro azobenzene (NHA) and 4-amino-4 ‘-nitro azobenzene (DO3) were prepared respectively from p-nitrophenylamine as a precursor compound. Two kinds of doped organic/inorganic hybrid nonlinear optical (NLO) materials containing NHA and DO3 were synthesized by Sol-Gel process. The preparation and properties of two NLO materials were studied and characterized by FTIR, IH-NMR, UV-VIS, SEM, DSC and SHG measurements. The results show that the maximum doping amounts of NHA and DO3 in two doped hybrid NLO materials are 7.2(wt)% and ll.3(wt)% respectively, and the corresponding second-order NLO coefficients (d33values) are 2.91 ×l0^-3esu and 6.14×10 -8 esu. Two doped NLO materials have relatively good RT stability, after 90 days at RT the d33 values can maintain about 85% of their initial values, but after l0h at 100℃ can only maintain about 50% of their initial values. In this report, the reasons for high-temperature instability of doped materials were discussed, and the possible improvements were also suggested. 相似文献
976.
硒酵母中硒含量测定方法的研究 总被引:19,自引:2,他引:19
报道了人工培养硒酵母中总硒、无机硒和有机硒的测定方法,建立了无机硒和有机硒的鉴别方法,并采用透析处理法使硒酵母中的无机硒和有机硒得以分离;还报道了不同培养条件下得到的5种硒酵母中总硒、无机硒和有机硒的定量分析数据,为硒酵母在医药和添加剂领域的应用提供了可靠的数据。 相似文献
977.
978.
979.
980.
Summary The retention behavior of phenylamine and naphthylamine sulphonic acid was evaluated in reversed-phase ion-pair liquid chromatography as a function of organic modifier concentration and column temperature. It has been observed that the logarithm of capacity factors decrease linearly with organic modifier concentration, and there is a good linear relationship between the intercept and slope for this relationship. Phenylamine and naphthylamine sulphonic acid retention decreases with increase in column temperature. A linear dependence of lnk
ip
on the reciprocal of the absolute temperature, the Van't Hoff plot, was observed over the column temperature range studied, and the standard enhalpic change (Ho) for these sulphonic acid transfers from the mobile phaser to the stationary phase was determined. Ho was dependent on the solute structure and in the range from 2.5 Kcal/mol to 5.5 Kcal/mol, which is close to that observed in RP-HPLC. The enthalpy/entropy compensation effect was evaluated by plotting lnk
ip(T)
vs. –Ho, and the apparent differences in retention mechanisms between the analytes were observed, which may arise from the significant differences in their configuration, hydrophobicity and the charges of the solutes as well as the complex retention processes of RP-IPC. 相似文献