排序方式: 共有14条查询结果,搜索用时 31 毫秒
1.
2.
The enantiomers of some amino acids have been separated on commercial chiral TLC plates in reversed-phase mode. The effect
of the pH* of the aqueous-organic mobile phase on the retention and mobility of the enantiomers and on selectivity was investigated.
It was shown that for most of the amino acids investigated the highest enantioselectivity was obtained at pH* 3–4 or 6–7.
The drift and disturbance of the baseline on the chromatograms were also much smaller at pH* 3–4 and 6–7. 相似文献
3.
4.
用19F NMR研究了噻吩甲酰三氟丙酮铝与苯甲酰丙酮铝体系分子间的团体交换反应,求得了交换反应的平衡常数及自由能,结果表明交换反应有利于混合配体络合物生成,平衡时混和溶液中各组分分布偏离统计分布。 相似文献
5.
6.
手性配位体交换流动相添加剂法拆分对映体 总被引:7,自引:0,他引:7
综述了手性配合基交换色谱法通常采用三种手性相系统中的流动相添加剂方法。主要内容有:(A)手性配合基交换机制,给出了描述对映体对在色谱系统中的保留时间和分离选择性的公式,包括手性选择剂在固定相和流动相中的各种不同情况。公式表明整个色谱往系统的对映体选择性不同于溶液中所存在的选择剂与被选择物作用的情况;(B)影响配合交换的参数,讨论了金属离子、金属离子/配位体比率、金属离子络合物浓度、固定相、流动相pH、洗脱顺序、有机调节剂、离子对试剂、流动相离子强度、温度、立体选择性和手性交互识别;(C)应用。 相似文献
7.
8.
《Analytical letters》2012,45(4):867-882
Abstract The enantiomeric separation by high-performance liquid chromatography of underivatized non-protein amino acids was investigated by using a column packed with octadecylsilanized silica coated with N,S-dioctyl-D-penicillamine as a chiral ligand-exchange phase (Sumichiral OA-5000). Excellent to good separations of enantiomers were achieved with a variety of nonprotein amino acids carrying aliphatic or aromatic side-chains by optimizing the amount (0-20%, v/v) of the organic component (2-propanol) and the concentration (1-5 mM) of the complexing metal ion (Cu2+) in the hydro-organic eluent. 相似文献
9.
The successful enantioseparation of five 6-desfluoroquinolones with three polysaccharide-based stationary phases (namely, the cellulose-based Chiralpak IB and the two amylose-based Chiralpak AD-H and Lux Amylose-2) is herein described. The investigated species differ for the nature of substituents and/or the position of the stereogenic centre on the quinolone scaffold.The effect on the enantioseparation performance exerted by the different morphology of the cellulose-based and amylose-based polymers, was systematically evaluated for all compounds. In this frame, the impact of alternative alcoholic (ethanol, 2-ethoxyethanol, methanol, 2-propanol) and acidic (acetic, methanesulfonic and trifluoroacetic acid) modifiers as well as of a “non-standard” solvent (chloroform), was investigated in normal phase conditions along with the stereo-electronic peculiarities of the selected polymers. While 7-[4-(1,3-benzothiazol-2-yl)-2-methyl-1-piperazinyl]-1-methyl-4-oxo-1,4-dihydro-1,8-naphthyridine-3-carboxylic acid (1) was enantioresolved with conventional normal-phase conditions by means of the largely employed amylose-based Chiralpak AD-H column, the recruitment of a bulky alcohol (2-ethoxyethanol) succeeded in the enantioresolution of 6-amino-1-methyl-7-[2-methyl-4-(2-pyridinyl)-1-piperazinyl]-4-oxo-1,4-dihydro-3-quinolinecarboxylic acid (2) and 6-amino-1-[1-(hydroxymethyl)propyl]-4-oxo-7-(4-pyridin-2-ylpiperazin-1-yl)-1,4-dihydroquinoline-3-carboxylic acid (3) with the same column. The use of the amylose-based Lux Amylose-2 column, carrying both an electro-withdrawing (chlorine) and an electro-donating (methyl) group on the carbamate residue, allowed to get 6-amino-1-methyl-4-oxo-7-[3-(2-pyridinyl)-1-pyrrolidinyl]-1,4-dihydro-3-quinolinecarboxylic acid hydrochloride (4) enanantioresolved, and 6-amino-1-methyl-4-oxo-7-(3-pyridin-2-ylpiperidin-1-yl)-1,4-dihydroquinoline-3-carboxylic acid (5) enantioseparated. 相似文献
10.
In this study, we have proposed a novel organophosphate mimic surface molecular imprinted polymer for selective binding of the nerve agent by chitosan–Cd(II) as a new metal-chelating monomer via metal coordination–chelation interactions and dimethoate templates. We have improved a method for the selective binding behavior of dimethoate compounds on the surface of molecular imprinted polymer, which was prepared using ligand-exchange (chitosan–Cd(II)) monomers. The influence of ligand exchange imprinting on the creation of recognition sites toward dimethoate has determined application of adsorption isotherms. The effect of initial concentration of dimethoate, adsorption time, and imprinting efficiency on the adsorption selectivity for molecular imprinted polymer-ligand exchange has been investigated. The number of accessible sites (Qmax), relative selectivity coefficients (k′), and binding abilities have also been evaluated. Then, molecular imprinted polymer-ligand exchange was treated with formaldehyde to remove dimethoate templates. 相似文献