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101.
102.
Zirconia—A stationary phase capable of the separation of polar markers of myocardial metabolism in hydrophilic interaction chromatography 下载免费PDF全文
Radim Kučera Petra Kovaříková Ivana Pasáková‐Vrbatová Jitka Slaninová Jiří Klimeš 《Journal of separation science》2014,37(9-10):1089-1093
Creatine, phosphocreatine, and adenine nucleotides are highly polar markers of myocardial metabolism that are poorly retained on RP silica sorbents. Zirconia represents an alternative material to silica with high promise to be used in hydrophilic interaction chromatography (HILIC). This study describes a first systematic investigation of the ability of ZrO2 to separate creatine, phosphocreatine, adenosine 5′‐monophosphate, adenosine 5′‐diphosphate, and adenosine 5′‐triphosphate and compares the results with those obtained on TiO2. All analytes showed a HILIC‐like retention pattern when mobile phases of different strengths were tested. Stronger retention and better column performance were achieved in organic‐rich mobile phases as compared to aqueous conditions, where poor retention and insufficient column performance were observed. The effect of mobile phase pH and ionic strength was evaluated as well. The analysis of myocardial tissue demonstrated that all compounds were separated in a relevant biological material and thus proved ZrO2 as a promising phase for HILIC of biological samples that deserves further investigation. 相似文献
103.
Evaluation of differences between Chiralpak IA and Chiralpak AD‐RH amylose‐based chiral stationary phases in reversed‐phase high‐performance liquid chromatography 下载免费PDF全文
Polysaccharide‐based chiral stationary phases can be used for the enantioselective separation of a wide range of structurally different compounds. These phases are available with chiral selectors coated or immobilized on silica gel support. The means of attachment of the chiral selector to the carrier can influence the separation performance of these stationary phases. This paper deals with evaluation of differences in the separation abilities of coated Chiralpak AD‐RH versus immobilized Chiralpak IA amylose‐based stationary phases in the reversed–phase mode of high–performance liquid chromatography. A set of chiral analytes was separated under acidic and basic conditions. Differences were observed in the enantioseparation potential of the tested phases. The linear‐free energy relationship and additional evaluation of ionic interactions were used to ascertain whether the interactions that participate in retention and enantioseparation are affected by the means of preparation of these phases. All the interactions covered by the linear‐free energy relationship were significant for the studied phases and their absolute values were almost always higher for the coated phase. Ionic interactions were found to be more important on the immobilized stationary phase but did not contribute to any improvement in the enantioselective separation performance. 相似文献
104.
Martin Pavlita Radim Bína Zdenk ernoek Milan Erben Jaromír Vinklrek Ivan Pavlík 《应用有机金属化学》2005,19(1):90-93
Raman spectroscopy was used as a very simple and convenient tool for the detection of bent metallocene fragments [M(Cp)2]2+ (Cp = η5‐cyclopentadienyl ring; M = early transition metal) both in solid state and in solution. The rules were formulated and tested on the group of titanium complexes containing one or two η5‐bonded cyclopentadienyl rings, as well as on a series of model α‐amino acid complexes of antitumour active titanocene and vanadocene dichlorides. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
105.
Five cationic complexes of the general formula [Cp′2Ti(A)2]2+ [Cl?]2 [Cp′ = η5‐(CH3)C5H4 and A = glycine, 1 ; 2‐methylalanine, 2 ; N‐methylglycine, 3 ; L ‐alanine, 4 ; and D ‐alanine 5 ] were prepared by the reaction of Cp′2TiCl2 and the appropriate α‐amino acid in 1:2 molar ratio from methanol–water solution in high yield. Air‐stable crystalline solids, highly soluble in water, were characterized by means of elemental analysis, IR, Raman, 1H, 13C and 14N NMR spectroscopy. The structure of compound 3 was determined by single crystal X‐ray crystallography: orthorhombic Pbca No. 61, a = 9.5310(3), b = 18.2980(5), c = 26.6350(5) Å, V = 4654 Å3, Z = 8. Hydrolytic stability of all compounds in D2O was investigated using 1H NMR spectroscopy within the pD interval of 2.9–6.5. All compounds slowly decomposed during 24 h at pD = 2.94, forming a mixture of hydrolytic products [Cp′2Ti(A)(D2O)]2+, [Cp′2Ti(D2O)2]2+ and respective α‐amino acids. By elevating pD to 4.0 and up to 6.5, a yellowish precipitate was formed, which indicates decomposition of the complexes. These compounds were characterized using elemental analyses, IR and Raman spectroscopy and attributed to oligomeric and/or polymeric structures described empirically by the formula Ti(Cp′)xOy(OH)z (x = 0.65; y = 0.3, z = 1.9). Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
106.
The crystal network of [Cp′2Ti(N?CH3? Gly)2]2+[Cl?]2 (Cp′ = (CH3)C5H4) complex, which crystallizes as a solvate with CH3OH, is built up with discrete cationic units connected through intermolecular H· · ·Cl bonds. The α‐amino acid ligands are attached through an intramolecular H· · ·O bond within one cationic unit. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
107.
Interactions of the “piano‐stool” [ruthenium(II)(η6‐arene)(quinolone)Cl]+ complexes with water; DFT computational study 下载免费PDF全文
Tereza Zábojníková Radim Cajzl Jakob Kljun Zdeněk Chval Iztok Turel Jaroslav V. Burda 《Journal of computational chemistry》2016,37(19):1766-1780
Full optimizations of stationary points along the reaction coordinate for the hydration of several quinolone Ru(II) half‐sandwich complexes were performed in water environment using the B3PW91/6‐31+G(d)/PCM/UAKS method. The role of diffuse functions (especially on oxygen) was found crucial for correct geometries along the reaction coordinate. Single‐point (SP) calculations were performed at the B3LYP/6‐311++G(2df,2pd)/DPCM/saled‐UAKS level. In the first part, two possible reaction mechanisms—associative and dissociative were compared. It was found that the dissociative mechanism of the hydration process is kinetically slightly preferred. Another important conclusion concerns the reaction channels. It was found that substitution of chloride ligand (abbreviated in the text as dechlorination reaction) represents energetically and kinetically the most feasible pathway. In the second part the same hydration reaction was explored for reactivity comparison of the Ru(II)‐complexes with several derivatives of nalidixic acid: cinoxacin, ofloxacin, and (thio)nalidixic acid. The hydration process is about four orders of magnitude faster in a basic solution compared to neutral/acidic environment with cinoxacin and nalidixic acid as the most reactive complexes in the former and latter environments, respectively. The explored hydration reaction is in all cases endergonic; nevertheless the endergonicity is substantially lower (by ~6 kcal/mol) in basic environment. © 2016 Wiley Periodicals, Inc. 相似文献
108.
Pavlína Ginterová Joanna Znaleziona Radim Knob Michal Douša Jan Petr Juraj Ševčík 《Chemical Papers》2016,70(8):1024-1030
The capillary zone electrophoresis method was developed for the chiral separation of R,S-cinacalcet. Cyclodextrins with different substituents were tested in both acidic and alkaline background electrolytes. The non-ionic cyclodextrin, 2-hydroxypropyl-γ-cyclodextrin, was selected as the best chiral selector. The separation was performed using a positive voltage in a phosphate buffer at pH 2.5. The analytes studied were separated within 12 min. The proposed method was applied to the analysis of tablets containing R-cinalcalcet as the active substance. The enantiopurity of R-cinacalcet in the tablets studied was confirmed. Subsequently, the analysis of tablets spiked with S-cinacalcet (chiral impurity) was also performed. The method here presented makes possible the determination of 0.1 % of S-cinacalcet in tablets. The analytical characteristics of the method, such as linearity, recovery and RSD values of the peak area and the migration time, were evaluated. The inter-day RSD values of the peak area and the migration time were lower than 3.71 % and 1.3 %, respectively. 相似文献
109.
McGovern MM Elles R Beretta I Somerville MJ Hoefler G Keinanen M Barton D Carson N Dequeker E Brdicka R Blazkova A Aymé S Schnieders B Muller CR Dalen V Martinez AA Kristoffersson U Ozguc M Mueller H Boone J Lubin IM Sequeiros J Taruscio D Williamson B Mainland L Yoshikura H Ronchi E 《Community genetics》2007,10(3):123-131
110.
Viñas C Laromaine A Teixidor F Horáková H Langauf A Vespalec R Mata I Molins E 《Dalton transactions (Cambridge, England : 2003)》2007,(31):3369-3377
The structurally chiral [7-(2'-pyridyl)-7,8-nido-C(2)B(9)H(11)](-), [](-), anion was prepared by a partial degradation reaction of 1-(2'-pyridyl)-1,2-closo-C(2)B(10)H(11). From this anion a protonated specie, H[7-(2'-pyridyl)-7,8-nido-C(2)B(9)H(11)] , and a tetramethylammonium salt, [NMe(4)][7-(2'-pyridyl)-7,8-nido-C(2)B(9)H(11)], [NMe(4)][] can be obtained. The (1)H{(11)B} DNMR study on in the temperature range from 298 to 203 K identified the weakly basic nitrogen atom in the pyridine ring as the proton accepting site in solid state and low temperature and revealed pronounced weakening of the nitrogen-proton interaction while the temperature increases. Capillary electrophoresis and X-ray diffraction confirmed the pyridine nitrogen atom as the proton binding site. Separation of the electrophoretically pure racemic [7-(2'-pyridyl)-7,8-nido-C(2)B(9)H(11)](-) ion into two peaks by the chiral selector beta-cyclodextrine has been achieved. 相似文献