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41.
R. Nowka I. L. Marr T. M. Ansari H. Müller 《Fresenius' Journal of Analytical Chemistry》1999,364(6):533-540
Solid sampling graphite furnace atomic absorption spectroscopy (SS-GFAAS) has been used for the determination of traces of
heavy metals (Cd, Pb, Cu, Cr, Ni, V and As) in barytes over a wide concentration range, e.g. Cd from 0.023 to 27.0 μg/g and
Pb from 1.54 to 3509 μg/g.The necessity of determining heavy metals in commercial barytes (naturally occurring barium sulfate),
a mineral important to the oil industry because of its use in drilling muds, is discussed. The problems presented by the analysis
of this difficult matrix are elegantly solved by using SS-GFAAS for the direct determination of heavy metals. A high-performance
graphite furnace AAS with D2-background correction system and a transversely heated graphite atomizer was used for the investigations. The spectrometer
was combined with a mechanical sampling module and an ultramicrobalance. The transfer of solid samples (sample weights 0.031–0.686
mg) into the atomizer was carried out by using an optimized graphite platform as the sample carrier. Calibration curve techniques
and standard addition methods were employed using external standards (CRMs). Problems associated with signal deformations
like multiple peaks, tailing or shoulders are also discussed and possibilities to solve the problems are given. The influence
of the homogeneity of solid samples on the precision and accuracy are shown in a real example. The results obtained by SS-GFAAS
were compared with results by other methods like X-ray fluorescence spectroscopy (XRF) and flame AAS after aqua regia microwave extraction. This study has demonstrated that SS-GFAAS is a very powerful and easy-to-use method for quick and accurate
analysis of barytes.
Received: 9 November 1998 / Revised: 29 January 1999 / Accepted: 2 February 1999 相似文献
42.
43.
Abedinifar Fahimeh Babazadeh Rezaei Elham Biglar Mahmood Larijani Bagher Hamedifar Halleh Ansari Samira Mahdavi Mohammad 《Molecular diversity》2021,25(4):2571-2604
Molecular Diversity - Thiophene-based analogs have been fascinated by a growing number of scientists as a potential class of biologically active compounds. Furthermore, they play a vital role for... 相似文献
44.
Mashaallah Rahmani Massoud Kaykhaii Zahra Safari Ommolbanin Ansari Shahrzad Jaberi Nasab 《Chromatographia》2017,80(1):109-117
Three new dispersive liquid–liquid microextraction (DLLME) methods, air-assisted (AA-DLLME), vortex-assisted (VA-DLLME) and ultrasound-assisted (UA-DLLME), were compared from the point of view of their analytical application for preconcentration of trace amounts of benzene, toluene, ethylbenzene and xylene isomers (BTEX) in water samples. In all of these methods, no dispersive solvent is required and dispersion of extractant is carried out by air bubbles, vortex and ultrasound for AA-DLLEM, VA-DLLME, and UA-DLLME, respectively. Advantages and disadvantages of these three liquid phase microextraction methods and their capability in dispersion of a similar extractant phase in sample solutions were comprehensively compared. All other extraction parameters, which have an influence on the microextraction, were also investigated and optimized. Under optimized conditions, analytical figures of merit for the three techniques were determined and compared. It was found that the limit of detection of the three methods is almost the same, while AA-DLLME has a wider linear dynamic range and the shortest analysis time. Enrichment factors of 182, 45 and 245 were achieved for AA-DLLEM, VA-DLLME, and UA-DLLME, respectively. 相似文献
45.
Eugenol, the major constituent of clove oil, has been widely used for its anesthetic and analgesic action in dentistry. Eugenol exhibits pharmacological effects on almost all systems and our aim is to review the research work that has identified these pharmacological actions. Eugenol possesses significant antioxidant, anti-inflammatory and cardiovascular properties, in addition to analgesic and local anesthetic activity. The metabolism and pharmacokinetics of the compound in humans have been studied. Eugenol has also been used as a penetration enhancer. The compound is a very promising candidate for versatile applications, and the design of new drugs based on the pharmacological effects of eugenol could be beneficial. 相似文献
46.
The Er3+ -Yb3+ codoped in Li2O content tungsten -tellurite (TWL) transparent glasses are synthesized and measured the absorption, Raman and upconversion
luminescence (UPL) spectra. At room temperature intense green emission peak at 560 nm ( 4S3/2→4I15/2) and red emission peak at 670 nm ( 4F9/2→4I15/2) of Er3+ observed even at minimum 86 mW pumping power of infrared 980 nm excitation. For structure of the TWL glass, Raman spectrum
result revealed that an important role of WO3 in the formation of glass network linkage with Li2O. Under this influence estimated lifetime of the 4I11/2 of Er3+ was 1.89 μs and due to lower phonon energy of the glass produce strong upconversion signal. The effect of Er2O3 concentration on emission intensity result indicated that green emission intensity initially increase in compare to red emission.
Under the 980 nm pump power variation measured the relatively increases the red emission to the green emission intensity and
analyze the possible upconversion mechanism and process. 相似文献
47.
48.
Intikhab A. Ansari 《Physica C: Superconductivity and its Applications》2010,470(22):2078
Here, I present the reply to the comments from Mamedov regarding numerical solution of Bloch–Gruneisen function to determine the contribution of electron–phonon interaction in polycrystalline superconductor. Reply to the comments from Mamedov is discussed one by one. 相似文献
49.
50.
Influence of radiation on unsteady hydromagnetic natural convection transient flow near an impulsively moving vertical flat
plate with ramped wall temperature in a porous medium is studied. Exact solution of momentum and energy equations, under Boussinesq
approximation, is obtained in closed form by Laplace transform technique. The variations in fluid velocity and temperature
are shown graphically whereas numerical values of skin friction and Nusselt number are presented in tabular form. 相似文献