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171.
JPC – Journal of Planar Chromatography – Modern TLC - Two-dimensional thin-layer chromatography (2D TLC) has been used as a screening method for detection of the metal ions Al3+, Cr3+,... 相似文献
172.
A method for the determination of total mercury in coal fly ash by gold amalgamation cold vapour atomic absorption spectrometry (CV-AAS) was optimized. Most of the experiments were performed on NBS SRM 1633a Coal Fly Ash with a certified value of 160 ± 10 ng Hg g?1. The main attention was focused on the decomposition of the sample. The efficacy of pressure decompositions in closed silica and sealed Pyrex tubes using various combinations of acids (HNO3, HCl, HClO4) was compared with oxidative combustion of the coal fly ash. Notwithstanding the incomplete mineralization of the sample in sealed tubes, the results obtained showed good agreement with the certified value and results obtained by neutron activation analysis (NAA), which suggests that mercury is quantitatively released from the sample into solution. Lower results were obtained using decomposition in closed (but not hermetically sealed) silica tubes owing to losses of mercury by volatilization during decomposition. Interferences from some metal ions (nickel, lead, copper, silver, palladium, zinc and antimony) were also examined. The results showed a serious depression of the mercury signal only when gold, palladium and platinum were present at higher concentrations, which never or very seldom occur in fly ash matrices, and therefore do not represent a limitation of the method. 相似文献
173.
Simultaneous determination of inorganic mercury and methylmercury compounds in natural waters 总被引:3,自引:0,他引:3
The purpose of the present work was to develop a simple, rapid, sensitive and accurate method for the simultaneous determination of inorganic mercury (Hg(2+)) and monomethylmercury compounds (MeHg) in natural water samples at the pg L(-1) level. The method is based on the simultaneous extraction of MeHg and Hg(2+)dithizonates into an organic solvent (toluene) after acidification of about 300 mL of a water sample, followed by back extraction into an aqueous solution of Na(2)S, removal of H(2)S by purging with N(2), subsequent ethylation with sodium tetraethylborate, room temperature precollection on Tenax, isothermal gas chromatographic separation (GC), pyrolysis and cold vapour atomic fluorescence spectrometric detection (CV AFS) of mercury. The limit of detection calculated on the basis of three times the standard deviation of the blank was about 0.006 ng L(-1) for MeHg and 0.06 ng L(-1) for Hg(2+)when 300 mL of water was analysed. The repeatability of the results was about 5% for MeHg and 10% for Hg(2+). Recoveries were 90-110% for both species. 相似文献
174.
In this paper we study the local theta correspondences between epipelagic supercupsidal representations of a type I classical dual pair \((G,G')\) over p-adic fields. We show that, besides an exceptional case, an epipelagic supercupsidal representation \(\pi \) of \({\widetilde{G}}\) lifts to an epipelagic supercupsidal representation \(\pi '\) of \({\widetilde{G}}'\) if and only if the epipelagic data of \(\pi \) and \(\pi '\) are related by the moment maps. 相似文献
175.
Monika Horvat Martina Avbelj María Beatriz Durn-Alonso Mihailo Banjanac Hrvoje Petkovi Jernej Iskra 《Molecules (Basel, Switzerland)》2021,26(22)
The current COVID-19 outbreak has highlighted the need for the development of new vaccines and drugs to combat Severe Acute Respiratory Syndrome-Coronavirus-2 (SARS-CoV-2). Recently, various drugs have been proposed as potentially effective against COVID-19, such as remdesivir, infliximab and imatinib. Natural plants have been used as an alternative source of drugs for thousands of years, and some of them are effective for the treatment of various viral diseases. Emodin (1,3,8-trihydroxy-6-methylanthracene-9,10-dione) is a biologically active anthraquinone with antiviral activity that is found in various plants. We studied the selectivity of electrophilic aromatic substitution reactions on an emodin core (halogenation, nitration and sulfonation), which resulted in a library of emodin derivatives. The main aim of this work was to carry out an initial evaluation of the potential to improve the activity of emodin against human coronavirus NL63 (HCoV-NL63) and also to generate a set of initial SAR guidelines. We have prepared emodin derivatives which displayed significant anti-HCoV-NL63 activity. We observed that halogenation of emodin can improve its antiviral activity. The most active compound in this study was the iodinated emodin analogue E_3I, whose anti-HCoV-NL63 activity was comparable to that of remdesivir. Evaluation of the emodin analogues also revealed some unwanted toxicity to Vero cells. Since new synthetic routes are now available that allow modification of the emodin structure, it is reasonable to expect that analogues with significantly improved anti-HCoV-NL63 activity and lowered toxicity may thus be generated. 相似文献
176.
177.
Mercury as a global pollutant 总被引:5,自引:0,他引:5
Milena Horvat 《Analytical and bioanalytical chemistry》2002,374(6):981-982
178.
P. Gordan 《Mathematische Annalen》1871,3(3):355-414
Ohne Zusammenfassung 相似文献
179.
Paul Gordan 《Mathematische Annalen》1892,40(4):503-526
Ohne Zusammenfassung 相似文献
180.
Flutelike porous hematite nanorods and branched nanostructures: synthesis, characterisation and application for gas-sensing 总被引:1,自引:0,他引:1
Gou X Wang G Kong X Wexler D Horvat J Yang J Park J 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(19):5996-6002
Flute-like porous alpha-Fe2O3 nanorods and branched nanostructures such as pentapods and hexapods were prepared through dehydration and recrystallisation of hydrothermally synthesised beta-FeOOH precursor. Transmission electron microscopy (TEM), high-resolution TEM and selected area electron diffraction analyses reveal that the nanorods, which grow along the [110] direction, have nearly hollow cavities and porous walls with a pore size of 20-50 nm. The hexapods have six symmetric arms with a diameter of 60-80 nm and length of 400-900 nm. The growth direction of the arms in the hexapod-like nanostructure is also along the [110] direction, and there is a dihedral angle of 69.5 degrees between adjacent arms. These unique iron oxide nanostructures offer the first opportunity to investigate their magnetic and gas sensing properties. The nanostructures exhibited unusual magnetic behaviour, with two different Morin temperatures under field-cooled and zero-field-cooled conditions, owing to their shape anisotropy and magnetocrystalline anisotropy. Furthermore, the alpha-Fe2O3 nanostructures show much better sensing performance towards ethanol than that of the previously reported polycrystalline nanotubes. In addition, the alpha-Fe2O3 nanostructure based sensor can selectively detect formaldehyde and acetic acid among other toxic, corrosive and irritant vapours at a low working temperature with rapid response, high sensitivity and good stability. 相似文献