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41.
A novel dynamic headspace gas chromatographic system equipped with a wide bore capillary column was constructed for direct analysis of less volatile components in polymeric materials such as coating paints. With this system, the determination of typical paint additives such as hindered amine light stabilizers and ultraviolet absorbers could be carried out within a short time. 相似文献
42.
对抚州地区秀茶场产的茶叶进行了微量元素测定,提供了五种茶的微量元素谱,同时还对比了秀谷茶场产茶和英德红茶中的微量元素含量的差异。 相似文献
43.
过渡金属络合物中过渡金属与配体间所形成的化学键的成键本质,可以在理论化学基础上,采用定量的方法进行分析。本文重点以铁羰基络合物为例,对常用的分析方法,如自然键轨道方法(NBO)、电荷分解分析(CDA)、分子中的原子(AIM)拓扑分析方法以及ETS和EDA能量分解方法等,在应用中的优缺点进行了分析和评述。借助于这些方法提供的电荷、能量和电子密度等配分项可以深刻认识和理解过渡金属-配体间形成的化学键的成键本质。 相似文献
44.
采用Hartree-Fock和MP2方法在多种水平下优化了(H2O)^+n(n =1,2)的几何结构,并进行了振动光谱分析。结果表明:对(H2O)^+采用MP2/6-311++G(d,p)可得出最满意的结论。 相似文献
45.
This article discusses the development of various analytical methods for identification and quantification of residues of antibiotics in meeting international regulatory requirements, and, as an example, overviews the screening, purification, fractionation and analytical assays of bacitracin, a commonly applied polypeptide antibiotic mixture. Attention is focused on the development of chemical methods, as they provide extraordinary performance, in terms of sensitivity and selectivity, for measuring residual levels of the various components of bacitracin in food and other matrices; the non-compound specific biological assay is discussed only briefly. Because of its advantages, state-of-the-art high-performance liquid chromatography (HPLC) coupled with various detection techniques, in particular mass spectrometry (MS), has recently gained in popularity in confirming and quantifying drug residues. In this article, the authors also outline the latest results on the application of highly sensitive and selective LC-MS in analysis of bacitracin residues in milk and animal tissues. LC-MS is suggested as the technique of choice for confirmation of polar polypeptide antibiotics and the like at trace concentrations. 相似文献
46.
Jochen Münchenberg Jens R. Goerlich Axel K. Fischer Peter G. Jones Reinhard Schmutzler 《无机化学与普通化学杂志》1996,622(2):348-354
Synthesis, Structure, and some Reactions of N-(N′,N′,N″,N″-tetramethyl)guanidinyl-substituted Phosphoryl Compounds The tetramethylguanidinyl-substituted phosphoryl compounds 1 – 10 were prepared in the reaction of the appropriate chlorophosphoryl compounds with either N′,N′,N″,N″-tetramethylguanidine (HTMG) or N-trimethylsilyl-(N′,N′,N″,N″-tetramethyl)guanidine (TMSTMG). With methyl iodide 1 reacted with N-alkylation to give the ammonium salt 11. 1 reacted with BF3 · Et2O at both imino nitrogen atoms with formation of the bis-BF3-adduct 12 . The X-ray structure determination of phenylphosphonic acid-bis(N′,N′,N″,N″-tetramethylguanidinide) 3 shows shortened PN-bonds and widened PNC-angles, consistent with the partial double bond character of the PN-bond. 相似文献
47.
V. Balek H. Hamerská L. Montanaro A. Negro 《Journal of Thermal Analysis and Calorimetry》1992,38(4):567-573
The results of the investigations of thermal behaviour of Li2ZrO3, prepared in the amorphous state by means of sol-gel technique are demonstrated. The thermal treatment was carried out in air under constant heating rate of 5 deg·min–1 and cooling rate of 2.5 deg·min–1. The methods of DTA, TG, Emanation Thermal Analysis (ETA) and dilatometry were used, for characterization of the thermal behaviour in dynamic conditions. The X-ray diffraction patterns were used for characterization of the phase changes observed by TA Methods.
Zusammenfassung Ergebnisse aus Untersuchungen des thermischen Verhaltens von Li2ZrO3, hergestellt mittels einer Sol-Gel-Technik im amorphen Zustand werden dargelegt. Die thermische Behandlung wurde in Luft bei einer konstanten Aufheizgeschwindigkeit von 5 Grad·min–1 und einer Abkühlgeschwindigkeit von 2,5Grad·min–1 durchgeführt. Zur Beschreibung des thermischen Verhaltens unter dynamischen Verhältnissen wurden DTA, TG, Emanationsthermoanalyse und Dilatometrie angewendet. Zur näheren Charakterisierung der bei TG beobachteten Phasenumwandlungen wurde Röntgendiffraktion verwendet.相似文献
48.
A high-performance thin-layer chromatographic (HPTLC) method is described for the determination of tributyltin compounds (bis(tri-n-butyltin) oxide, TBTO, and tri-n-butyltin naphthenate, TBTN) and their degradation products (dibutyltin and monobutyltin compounds). The organotin compounds are extracted from wood with ethanol containing 0.5% (v/v) of hydrochloric acid and the separation of the defferent kinds of organotin compounds is achieved by thin-layer chromatography. The sample spots are measured using a scanning densitometer after decomposing the organotin compounds to inorganic tin by ultraviolet irradiation and visualization of the spots with pyrocatechol violet. Applications of the method to detection and quantification of organotin compounds in preservative solutions, in recently impregnated wood, and in wood samples from five-year-old window frames are described. 相似文献
49.
50.
I. Kuselman 《Accreditation and quality assurance》1998,3(3):131-133
It is argued that results of uncertainty calculations in chemical analysis should be taken into consideration with some caution
owing to their limited generality. The issue of the uncertainty in uncertainty estimation is discussed in two aspects. The
first is due to the differences between procedure-oriented and result-oriented uncertainty assessments, and the second is
due to the differences between the theoretical calculation of uncertainty and its quantication using the validation (experimental)
data. It is shown that the uncertainty calculation for instrumental analytical methods using a regression calibration curve
is result-oriented and meaningful only until the next calibration. A scheme for evaluation of the uncertainty in uncertainty
calculation by statistical analysis of experimental data is given and illustrated with examples from the author's practice.
Some recommendations for the design of corresponding experiments are formulated. 相似文献