Impregnated silica-based layers in thin layer chromatography

Abstract

Impregnated thin-layer chromatography (TLC) layers based on silica gel are presented. Impregnating agents such as metal cations, inorganic ions, chelating agents, chiral selectors, surfactants, ion-pairing reagents, and ionic liquids are discussed. The role of impregnated TLC layers in medicinal chemistry is highlighted. The historical overview of TLC separations on physically coated layers is given and some future prospects ahead of this technique are discussed.     

Strychninium N‐phthaloyl‐β‐alaninate N‐phthaloyl‐β‐alanine and brucinium N‐phthaloyl‐β‐alaninate 5.67‐hydrate

Comparison of the structures of strychninium N‐phthaloyl‐β‐alaninate N‐phthaloyl‐β‐alanine, C₂₁H₂₃N₂O₂⁺·C₁₁H₈NO₄⁻·C₁₁H₉NO₄, and brucinium N‐phthaloyl‐β‐alaninate 5.67‐hydrate, C₂₃H₂₇N₂O₄⁺·C₁₁H₈NO₄⁻·5.67H₂O, reveals that, unlike strychninium cations, brucinium cations display a tendency to produce stacking inter­actions with cocrystallizing guests.     

Comparison of sulphur and sulphur–oxygen ligands as ionophores for liquid–liquid extraction and facilitated transport of silver and palladium

The reactivity of new ligands described as S₁, S₅, S₂O₉ (in respect to character and amount of donors) towards metal ions was examined by extraction from HNO₃ and HCl media. These ligands were next utilised as carriers for Ag and Pd transport through a supported liquid membrane (SLM). The effect of collecting a greater number of S donors in one molecule and the influence of type of donors (O–S versus S) on efficiency and selectivity of Ag and Pd(II) extraction and transport were examined.

The extraction of Ag from HNO₃ solutions increased with increasing amount of S-donors in one molecule (S₁2O₉5). For palladium the sequence was different (S₅12O₉). The transport of Ag through SLM impregnated with m-chlorotoluene solution of ionophore increased in the same order as in the case of extraction, whereas for Pd the row was different: S₅2O₉1. The highest fluxes of Ag and Pd transported from HNO₃ equalled to 5.25×10⁻⁷ and 1.37×10⁻⁷ mol/m² s, respectively. Palladium flux depended on stripping solution type (Na₂S₂O₃相似文献   

Application of a retention database to the identification of individual polychlorinated biphenyl congeners in Aroclors mixture using selected polychlorinated biphenyls as a reference series

The database of the relative retention times (RRTs) of polychlorinated biphenyls (PCBs) reported in literature was used to calculate the retention indices (RIs) of all 209 PCB congeners on temperature programmed capillary column Rtx-5. Calculation of retention indices was based on reference series of seven congeners (PCB IUPAC Nos. 18, 52, 101, 143, 185, 203 and 206) that exhibit linear relative retention time behaviour as a function of chlorine number. The calculated indices were compared to those determined in our laboratory as well as to those obtained by other authors. The proposed indices system was applied for identification individual congeners in mixture of Aroclors 1242:1254:1260, using only reference series of PCBs.     

Some physical properties of KCl+Pb2+ crystals

This paper presents the results of measurements of the mechanical and electrical properties of as-received pure and lead-doped crystals of potassium chloride. The critical resolved shear stress of the crystals obeys the Franks relationship in the whole concentration range. In addition, the correlation between ₀ and the Vickers hardness numberH was found and the equation is of the form ₀=k (H–H ₀). The solubility of Pb²⁺ in as-received KCl crystals was observed, from measurements of the electrical conductivity, to be low—the successive saturation of the solid solution started already in an environment of 5 mole ppm in agreement with data from the mechanical measurements. The density of cation vacancies and their mobility were represented by the following euqations ₁ T=6·25×10⁴ exp(–·75/kT) cm² K/volt. sec,n ₁=6·95×10²³ exp(–2·12/kT) vacancies/cm³ The value of 0sd46±0·02 eV was found as a rough estimate of the association energy.The authors wish to express their thanks to Professor Dr. J. Z.Damm and Ing. E.Mariani for their stimulating interest in the present work.     

To the role of positive ions in plasma nitridation

The method similar to that of determining the asymmetric componentf ₁ of electron distribution function was used to prove whether the nitrogen ions produced in discharge may be the very particles which directly influence magnesium nitridation in glow discharge. The amounts of created magnesium nitride on surfaces facing the anode and the cathode, and positive ion current to the plane double-probe were measured. It follows from experimental results that positive ions from bulk plasma are not decisive for nitride formation.The authors would like to thank Dr. V.Krejí and Dr. K.Maek for helpful discussions and critical notices.     

Homodiselenacalix[4]arenes: Molecules with Unique Channelled Crystal Structures

A synthetic route towards homodiselenacalix[4]arene macrocycles is presented, based on the dynamic covalent chemistry of diselenides. The calixarene inner rim is decorated with either alkoxy or tert‐butyl ester groups. Single‐crystal X‐ray analysis of two THF solvates with methoxy and ethoxy substituents reveals the high similarity of their molecular structures and alterations on the supramolecular level. In both crystal structures, solvent channels are present and differ in both shape and capacity. Furthermore, the methoxy‐substituted macrocycle undergoes a single‐crystal‐to‐single‐crystal transformation during which the molecular structure changes its conformation from 1,3‐alternate (loaded with THF/water) to 1,2‐alternate (apohost form). Molecular modelling techniques were applied to explore the conformational and energetic behaviour of the macrocycles.     

Application of Dried Blood Spots and Serum Samples for the Determination of Vitamin D Metabolites in the Group of Healthy Women and with Hashimoto’s Thyroiditis

Chromatographia - The relationship between Hashimoto's thyroiditis and vitamin D concentration was already presented in many studies. The aim of this study was to analyze the differences in the...