Thin-Layer Chromatographic Separation of Amino Acid Enantiomers using Ligand Exchange

Silica gel thin-layer plates covered with L-arginine and copper acetate were used for the separation of amino acid enantiomers, The chromatographic selectivity and the effects of plate different preparation methods, sample molecular structure and solvent compositions on resolution performance were also discussed.

Extraction and separation of heavy rare earths from chloride medium byα-aminophosphonic acid HEHAPP

The extraction and separation of heavy rare earths（REs） using newly synthesized a-aminophosphonic acid extractant 2-ethylhexyl-3-（2-ethylhexylamino）pentan-3-yl phosphonic acid（HEHAPP, HA） in nheptane were investigated from chloride medium. The extraction stoichiometries of lanthanum, gadolinium, yttrium and lutetium are determined to be REA3 by the slope analysis method. The favorable separation factors of adjacent heavy REs（Ⅲ）,i.e. β（Y/Ho）, β（Er/Y）,β（Tm/Er）,β（Yb/Tm） and β（Lu/Yb）, are determined to be1.87,1.36, 3.21,3.22 and 1.93, respectively, when extracted from a binary system at proper condition. The loading capacities of HA for Ho, Er, Yb and Lu increase in the order Ho 〈 Er 〈 Yb 〈 Lu with the values being 0.201, 0.205, 0.216 and 0.229 mol/L, respectively. So HA would be a potential extractant for the separation of heavy REs（Ⅲ）. Among inorganic acids such as H2 SO4, HNO3 and HCl, HCl is tested to be the most effective stripping agent.

Expert systems for HPLC in biochemistry—The knowledge base for selection of HPLC column system in the separation of amino acids, peptides and proteins

The strategy of expert system for high performance liquid chromatography was discussed, the attentions are mainly placed on the knowledge base for selection of column system, separation modes and detection modes in the analysis of amino acids, peptides and proteins.

Aqueous stability of rare earth and thorium elements during hydrochloric acid leaching of roasted bastnaesite

In order to study the aqueous stability of rare earth and thorium elements and the reaction mechanism of hydrochloric acid leaching of roasted bastnaesite,Eh-pH diagrams for La-,Nd-,Ce-,Th-（Cl）-（F）-H2 O systems at 20 ℃ were depicted using HSC Chemistry 6.0 software. Eh-pH diagrams of La-, Ce-,Nd-and Th-Cl-H2 O systems show that trivalent rare earth would be leached into solution by adjusting the acidity of the leaching solution, while tetravalent cerium and thorium would be remained in the leaching residue. And in the case that the pH value of the leaching solution is lower than 2, tetravalent cerium would be partially reduced by chlorine ions（Cl^-）, which is well agreed with the industrial production. It can be inferred from Eh-pH diagrams for the systems La-, Nd-,Ce-, Th-F-H2 O that the leached trivalent rare earth ions（RE^（3＋）） and tetravalent thorium ions（Th^（4＋）） are preferentially combined with fluorine ions（F） to form sediment during non-reductive acid leaching of roasted bastnaesite. However,when controlling the pH value of the leaching solution below 0, fluorine and tetravalent cerium in the roasted bastnaesite would be leached out in the form of soluble [CeF3]~＋ complex. That means the precipitation of REF3 and ThF4·2.5 H2 O can be avoided in the leaching step. According to Eh-pH diagrams for the system Ce-F-Cl-H2 O, [CeF3]~＋ in the leaching solution would be reduced to CeF3 precipitate in the presence of Cl^-, that is to say, tetravalent cerium and fluorine would be firstly leached out to form[CeF3]~＋,which would then be reduced to CeF3 precipitate by Cl^-in the hydrochloric acid leaching process of roasted bastnaesite.

Protein separation using a novel silica-based RPLC/IEC stationary phase modified with N-methylimidazolium ionic liquid

Ionic liquids（ILs） immobilized on silica as novel high performance liquid chromatography（HPLC）stationary phases have attracted considerable attention. However, it has not been applied to protein separation. In this paper, N-methylimidazolium IL-modified silica-based stationary phase（Silpr Mim）was prepared and investigated as a novel multi-interaction stationary phase charged positively for protein separation. The results indicate that all of the basic proteins tested cannot be absorbed on this novel stationary phase, whereas all of the acidic proteins tested can be retained, and the baseline separation of eight kinds of acidic protein standards can be achieved when performed in reversed phase/ion-exchange chromatography（RPLC/IEC） mode. Compared with commonly used commercial octadecylated silica（ODS） column, the novel stationary phase can show selectivity and good resolution to acidic proteins, which has a promising application in the separation and analyses of acidic proteins from the complex samples in proteomics. In addition, the chromatographic behavior of proteins, the effect of the ligand structure and the retention mechanism on this stationary phase were also investigated.

A two-dimensional microporous metal–organic framework for highly selective adsorption of carbon dioxide and acetylene

Solvothermal reaction of 3-aminoisonicotinic acid（Haina） and Cu（NO_3）_2·2.5H_2O gave a novel twodimensional（2D） microporous metal–organic framework, [Cu（aina）_2（DMF）]·DMF（1, DMF = N,N-dimethylformamide）. Single-crystal X-ray crystallographic study of compound 1 revealed that Cu（II）ions are linked by ainaàligands forming square grid-like layers, which stack together via multiple hydrogen bonding interactions. The solvent-free framework of 1a displayed considerable porosity（void = 46.5%） with one-dimensional（1D） open channels（4.7 ？ ？ 4.8 ？） functionalized by amino groups.Gas sorption measurements of 1 revealed selective carbon dioxide（CO_2） and acetylene（C_2H_2） adsorption over methane（CH_4） and nitrogen（N_2） at ambient temperature.