共查询到14条相似文献,搜索用时 15 毫秒
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建立了用薄层色谱分离紫杉醇和三尖杉宁碱的方法.方法中以正己烷-二氯甲烷-甲醇-三乙胺(体积比4.5∶3.5∶0.5∶1.0)四元体系为展开剂,在硅胶薄层板上成功地分离了紫杉醇和三尖杉宁碱,所得斑点清晰、无拖尾.同时以该体系为展开剂,使用薄层色谱法指导分离提取紫杉醇和三尖杉宁碱过程中反相色谱流分的合并,方法快速、简单、成本低,取得了满意的结果. 相似文献
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建立了薄层色谱-紫外可见分光光度法测定纸张样品水解液中单糖组成的方法。纸张样品水解后点样在以丙酮处理过的硅胶G薄层板上,以正丁醇∶乙酸乙酯∶异丙醇∶乙酸∶吡啶∶水=7∶20∶12∶7∶6∶5(体积比)为展开剂,以苯胺-草酸为显色剂,测定了单糖的Rf值。以1-萘酚为显色剂,测定了纸张样品水解液中的单糖含量,方法的线性关系较好,5种单糖的样品加标回收率为96.10%~98.18%。该方法分离效果好,操作简便,可用于纸张样品水解液中5种单糖的同时测定,从而为法庭科学中纸张的检验提供依据。 相似文献
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Rosanna Toniolo Nicolò Dossi Andrea Pizzariello Sabina Susmel Gino Bontempelli 《Electroanalysis》2011,23(3):628-636
Based on preliminary voltammetric investigations at unmodified and modified electrodes in aqueous solutions buffered at different pHs, a profitable thin layer dual‐electrode detector was developed for the selective and simultaneous determination of ascorbic acid (AA) and hydrogen peroxide present in the same samples. It consists of a small thickness (0.1 mm) cell, used as a detector for a flow injection system, in which a glassy carbon (GC) and a polyeugenol coated Pt electrode are encased. The GC electrode is selective for AA, thanks to the potential applied (0.3 V vs. Ag/AgCl,Cl?sat), while H2O2 alone can be oxidized at the Pt electrode (0.75 V), thanks to the size selectivity and electrostatic screen properties displayed by the polyeugenol coating layer which prevents oxidation of ascorbate anions. Repeatable sharp peaks (±4.5 %) were detected for both analytes over wide linear ranges (0.005–1.000 mM) and detection limits of about 10?6 M (176 ppb) and 5×10?7 M (16 ppb) were inferred for AA and H2O2 respectively. This flow injection approach was applied to the analysis of some orange‐taste soft drinks, used as prototype real samples, spiked with controlled amounts of both analytes, thus inferring good recoveries which pointed out that deviations never exceeding 5 % affected the relevant accuracy. 相似文献
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《Analytical letters》2012,45(15):3225-3237
ABSTRACT Two procedures were developed for simultaneous determination of benazepril hydrochloride (I) and hydrochlorothiazide (II) in pure, laboratory made mixtures and in pharmaceutical dosage form “Cibadrex tablets® using reversed phase high performance liquid chromatographic and thin layer chromatographic methods. For reversed phase HPLC, a new very sensitive, rapid, selective method was developed. The linearity ranges were 32-448 ng/20 μl and 40-560 ng/20 μl for benazepril hydrochloride and hydrochlorothiazide, respectively. The corresponding recoveries were 99.38 ± 1.526 and 99.2 ± 1.123. The minimum detection limits were 7 ng/20 μl and 14 ng/20 μl for benazepril hydrochloride and hydrochlorothiazide respectively. On the other hand, a new, simple, sensitive and fast thin layer chromatographic scanning densitometric method was developed for simultaneous determination of benazepril hydrochloride and hydrochlorothiazide using ethyl acetate: methanol: ammonia (85: 20: 10 v/v) as the developing system. The Rf values were 0.33 & 0.68 for benazepril hydrochloride and hydrochlorothiazide respectively. The minimum detection limit obtained was 0.12 μg/spot for benazepril hydrochloride and 0.24 μg/spot for hydrochlorothiazide. The mean percentage recoveries were 100.04 ± 1.102 and 99.31 ± 1.009 for benazepril hydrochloride and hydrochlorothiazide respectively. The two proposed methods were simple, precise, sensitive and could be successfully applied for the determination of pure, laboratory made mixtures and pharmaceutical dosage forms. The results obtained were compared with those obtained by A 1%. 相似文献
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《Electroanalysis》2005,17(11):959-964
This article reports in situ FTIR monitoring of electrochemical reactions using a silicon‐based thin‐layer cell realized by micromachining fabrication technologies. The proposed device contains a silicon micromachined cavity cell integrated with a gold working electrode, a counter electrode, and a Ag/AgCl reference electrode. Electrochemical, spectroscopic, and spectroelectrochemical characteristics of the fabricated cell have been experimentally measured and exhibited a comparable performance to commercialized CaF2 thin‐layer cells. In situ spectroelectrochemical characteristics have been successfully tested for both 2 mM K3Fe(CN)6 in an aqueous solution and 2 mM ferrocene in a dichloromethane solution using the fabricated thin‐layer cell. 相似文献
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Jerzy Jurczyk Rafał Sitko Beata Zawisza Franciszek Buhl Ewa Malicka 《Mikrochimica acta》1999,132(1):41-47
A simple and quick method of durable samples preparation by the thin layer method through direct digesting of the analysed
material on the substrate has been presented. Four- and three-component mono- and polycrystals have been analysed. Standards
have been used in calibration containing: Cr, Co, Ni, Cu, Zn, Ga, Se, Sb, Yb. To improve the correlation between the concentration
and the fluorescent radiation models of mathematical corrections have additionally been used: multiple linear regression,
Lucas-Tooth-Pyne model (L. T. P.) and de Jongh model (d. J.).
Statistical parameters: detection limits for 0.5 mg samples: Cr–0.041%, Co–0.034%, Ni–0.042%, Cu–0.053%, Zn–0.054%, Ga–0.057%,
Se–0.057%, Sb–0.113%, Yb–0.077%. Correlation coefficients: simple regression 0.9946–0.9997, multiple regression 0.9974–1.0000,
L. T. P. 0.9993–1.0000, d. J. 0.9995–1.0000.
Received August, 1, 1998. Revision March 25, 1999. 相似文献
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Rafał Sitko Beata Zawisza Jerzy Jurczyk Dariusz Bochenek Małgorzata Płoñska 《Mikrochimica acta》2004,144(1-3):9-15
A method of wavelength-dispersive XRF analysis of Pb(Zr,Ti)O3 type ferroelectric ceramics doped with Pb(Nb,Mn)O3 and Bi2O3 is presented. The major elements Pb, Zr, Ti and minor elements Nb, Mn, Bi were determined. Matrix effects were minimized by using the thin layer method. Standards of the same chemical composition but varied masses were prepared to simplify calibration. To minimize errors resulting from inhomogeneity of a mass per unit area, the internal standard was used. Preparation of the sample consisted in digesting 25mg of the materials (with nickel as the internal standard) in sulfuric acid, evaporating to dryness and digesting in nitric acid and hydrogen peroxide, filling up to 25mL, and dropping 0.5mL of the solution onto a substrate. Standard samples were prepared by dropping different amounts of the multielement solution onto the substrate. The residual standard deviation for the reference sample of mass from 0.25mg to 0.7mg was within the range of 0.001–0.009mg (correlation coefficient 0.998–0.999) for major elements and within the range of 0.00003–0.0009mg (correlation coefficient 0.989–0.993) for minor elements. The detection limits for 0.5mg samples were within the range of 0.015%–0.35% for manganese and zirconium, respectively. 相似文献
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M. Isabelle Büschges Dr. Rudolf C. Hoffmann Dr. Anna Regoutz Dr. Christoph Schlueter Prof. Dr. Jörg J. Schneider 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(38):9791-9800
Multilayered heterostructures comprising of In2O3, SnO2, and Al2O3 were studied for their application in thin-film transistors (TFT). The compositional influence of tin oxide on the properties of the thin-film, as well as on the TFT characteristics is investigated. The heterostructures are fabricated by atomic layer deposition (ALD) at 200 °C, employing trimethylindium (TMI), tetrakis(dimethylamino)tin (TDMASn), trimethylaluminum (TMA), and water as precursors. After post-deposition annealing at 400 °C the thin-films are found to be amorphous, however, they show a discrete layer structure of the individual oxides of uniform film thickness and high optical transparency in the visible region. Incorporation of only two monolayers of Al2O3 in the active semiconducting layer the formation of oxygen vacancies can be effectively suppressed, resulting in an improved semiconducting and switching behavior. The heterostacks comprising of In2O3/SnO2/Al2O3 are incorporated into TFT devices, exhibiting a saturation field-effect mobility (μsat) of 2.0 cm2 ⋅ V−1 s−1, a threshold-voltage (Vth) of 8.6 V, a high current on/off ratio (IOn/IOff) of 1.0×107, and a subthreshold swing (SS) of 485 mV ⋅ dec−1. The stability of the TFT under illumination is also altered to a significant extent. A change in the transfer characteristic towards conductive behavior is evident when illuminated with light of an energy of 3.1 eV (400 nm). 相似文献
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Summary A modified phenyl non-polar bonded-phase clean-up procedure for determining aflatoxin concentrations in aqueous acetone extracts of maize by bi-directional HPTLC was assessed. The accuracy and precision of the method was evaluated for a range of aflatoxin concentrations between 3.4 and 901 g/kg. The coefficients of variation varied between 1.7 and 10.8% with mean recoveries of 92–99%. Application of regression analysis revealed systematic errors for aflatoxins B2 (–0.36 to –1.19%) and G2 (–0.03 to –0.57), and small relative errors for all four toxins. The limits of detection were 1.7 g/kg (B1), 1.2 g/kg (B2), 0.9 g/kg (G1) and 0.8 g/kg (G2).The method was compared with the first action AOAC CB and Romer methods and a previously described PH bonded-phase procedure. It was found to recover significantly more aflatoxin from a sample of naturally contaminated maize, and to have accuracy better than and precision equivalent to the other methods. In addition, it was shown to be more rapid and cost effective than the AOAC methods. 相似文献
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Heinz Haschke 《Monatshefte für Chemie / Chemical Monthly》2003,134(4):595-617
Summary. Using a previously reported physical-mathematical (biokinetic) model which dealt with the factors influencing the development
of mismatch-dependent cells and DNA-proofreading and -repair and which model has been calibrated according to related experimental
data available in the literature or determined from own preliminary tests, the known efficacy of classical cancer-therapies
like surgical-tumor-extraction, or chemotherapy can be demonstrated via biokinetics. On the other hand, also other effects,
as they have been reported recently in the literature upon a significant increase of mutants in cases of an inhibition of
the proofreading and repair system, can be well described by the model.
Following the predictions of the model also in an opposite way, i.e. as to the consequences which arise, if the enzymatic proofreading- and repair-machinery were stimulated instead of inhibited,
an interesting chance for a new, “soft” cancer-therapy results. According to this, the administration of proofreading- and
repair-stimulators like f.e. equimolar combinations of purine- and pyrimidine-nucleotides’ precursors should open the possibility
for an adjuvant cancer-therapy, especially as a cancer-prophylaxis (i.e., against cancers “in statu nascendi”) but also as postsurgical safety-measure. The results of first preclinical tests are reported.
E-mail: Haschke.H@isovolta.com
Received June 26, 2002; accepted (revised) October 24, 2002 相似文献