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排序方式: 共有188条查询结果,搜索用时 15 毫秒
1.
2.
Summary Optically pure (+)-beta-eudesmol is a possible starting material for the synthesis of several termite defense compounds. A
two step procedure for the isolation of gram quantities of (+)-beta-eudesmol from commercially availableAmyris balsamifera oil (syn. West Indian sandalwood oil), containing 8% beta-eudesmol, was developed. Step one consisted of an efficient vacuum
distillation of the total oil. Step two was a medium pressure LC separation with an AgNO3 impregnated silica gel stationary phase. Several other separation procedures failed due to the presence of many closely related
sesquiterpene alcohols (75% of the oil). 相似文献
3.
The preparation of CuI + Ag2S and Cu2[HgI4] + Ag2S membranes hydrophobised by PTFE is described. The pressed membranes mounted in a multi-purpose all-solid-state electrode body have been examined as electrochemical sensors for Cu2+ and I– ions. For the electrode with (CuI + Ag2S + PTFE)-membrane experimental slopes of 29 mV(pCu)–1 and 62 mV(pI)–1 were obtained, in good agreement with the theoretical values. For practical measurement in solutions where both Cu2+ and I– can be present, the investigated electrode offers certain advantages in comparison with a commercial Cu-ISE. 相似文献
4.
G. Bigazzi S. Meloni M. Oddone G. Radi 《Journal of Radioanalytical and Nuclear Chemistry》1986,98(2):353-363
Iron and trace elements, such as rare-earth elements, scandium, rubidium, cesium, tantalum, thorium and uranium were determined by instrumental neutron activation analysis in geological samples of obsidian rocks from the Mediterranean Area and in obsidian artifacts found in some prehistorical human settlements in Italy. REE patterns and discriminant analysis allow a firm identification of the source material of artifacts, thus confirming and implementing fission track data of the same artifacts and rocks on the origin of the obsidian rock used to mould the artifacts. 相似文献
5.
The complexes of the reagent 5-Br-PADAP with the metal ions La(III), Ce(III), and Y(III) have been studied.The composition and stability of these complexes have been determined. A sensitive spectrophotometric procedure for the determination of the metal ions La(III), Ce(III), and Y(III) has been proposed. The limitations of this procedure and the effect of other ions have been studied. 相似文献
6.
The adsorptive behavior of the anti-inflammatory drug meloxicam was studied by cyclic, differentia-pulse and square-wave voltammetry on a hanging mercury drop electrode (HMDE). The drug was accumulated at HMDE and a well-defined stripping peak current was obtained at -1.42 V vs. Ag/AgCl (saturated KCl) electrode in acetate buffer solution (pH 5.0). A voltammetric procedure was developed for the determination of meloxicam using square-wave cathodic adsorptive stripping voltammetry (SW-CASV). The optimum working conditions for the determination of the drug were established. The analysis of meloxicam in human plasma was carried out satisfactorily. 相似文献
7.
Nj. Radić 《Mikrochimica acta》1985,85(3-4):209-218
Summary The preparation and performance of an Hg(II)-ISE are described. The analytical behaviour of this electrode, made by chemical treatment of a commercial silver sulphide type Pb(II)-ISE, is discussed in terms of potentialvs. concentration curves, potentialvs. pH curves, and selectivity. The response to fixed cHg(II) as the pH is increased in the alkaline region corresponds to decrease in the free Hg2+concentration down to pHg 17. The estimated limit of detection of total Hg(II) concentration is 10–5
M.
Presented at the Fifth European Conference on Analytical Chemistry (EUROANALYSIS-V), Cracow, Poland, 26–31 August, 1984. 相似文献
Potentiometrisches Verhalten einer handelsüblichen (Ag2S+PbS)-Membran-Elektrode gegenüber Hg(tt) in wäßriger Lösung
Zusammenfassung Herstellung und Wirkungsweise einer gegen Hg(II) ionenselektiven Elektrode wurde beschrieben. Das analytische Verhalten dieser Elektrode, die sich durch chemische Behandlung einer handelsüblichen Silbersulfidelektrode, die für Pb(II)-Ionen selektiv ist, herstellen läßt, wurde an Hand von Potential-Konzentrationskurven, Potential-pH-Kurven und ihrer Selektivität diskutiert. Das Verhalten gegenüber fixemc Hg(ii)bei Anstieg des pH ins alkalische Gebiet korrespondiert mit der Abnahme der Konzentration an freien Hg2+-ionen bis herab zu pHg 17. Die Nachweisgrenze liegt schätzungsweise bei einer totalen Hg(II)-Konzentration von 10–5 M.
Presented at the Fifth European Conference on Analytical Chemistry (EUROANALYSIS-V), Cracow, Poland, 26–31 August, 1984. 相似文献
8.
The preparation of CuI + Ag2S and Cu2[HgI4] + Ag2S membranes hydrophobised by PTFE is described. The pressed membranes mounted in a multi-purpose “all-solid-state” electrode body have been examined as electrochemical sensors for Cu2+ and I? ions. For the electrode with (CuI + Ag2S + PTFE)-membrane experimental slopes of 29 mV(pCu)?1 and 62 mV(pI)?1 were obtained, in good agreement with the theoretical values. For practical measurement in solutions where both Cu2+ and I? can be present, the investigated electrode offers certain advantages in comparison with a commercial Cu-ISE. 相似文献
9.
The voltammetric behaviour of chloroquine was investigated at carbon paste and dsDNA-modified carbon paste electrodes in different buffer systems over a wide pH range using cyclic and differential pulse voltammetry. Chloroquine was oxidized in the pH range 2.0-11.0 yielding one irreversible main oxidation peak. A second peak was also observed only in the pH range 5.0-7.0. The modification of the carbon paste surface with dsDNA allowed a preconcentration process to take place for chloroquine such that higher sensitivity was achieved as compared with the bare surface. The response was characterized with respect to solution pH, ionic strength, accumulation time and potential, chloroquine concentration, and other variables. Stripping voltammetric response showed a linear calibration curve in the range 1.0 × 10−7 to 1.0 × 10−5 mol l−1 with a detection limit of 3.0 × 10−8 mol l−1 at the dsDNA-modified electrode. Application of the modified electrode to serum, without sample pretreatment, resulted in good recovery higher than 95% and the higher standard deviation was 3.0%. 相似文献
10.
The oxidative behaviour of, a hypnotic drug, zolpidem was studied at glassy carbon electrode in Britton-Robinson buffer over the pH range 2.0-11.0 using cyclic, linear sweep and differential pulse voltammetry. Oxidation of the drug was effected in a single irreversible, diffusion-controlled step. Using differential pulse voltammetry (DPV), the drug yielded a well-defined voltammetric response in Britton-Robinson buffer, pH 8.0 at +0.889 V (vs. Ag/AgCl) on glassy carbon electrode. This process could be used to determine zolpidem concentrations in the range 5.0 x 10(-7) M to 1.0 x 10(-5) M with a detection limit of 2.0 x 10(-7) M. The method was applied, without any interference from the excipients, to the determination of the drug in a tablet dosage form. 相似文献