Chromatographic behaviour of alkaloids on thin layers of cation exchangers. II. Alginic acid, Rexyn 102, Dowex 50-X4 and CMCNa.

The chromatographic behaviour of 48 alkaloids on cation exchangers with cellulose, paraffin and polystyrene matrices in both the acid and sodium salt forms has been investigated. Water-organic solvent mixtures, aqueous buffer solutions and organic and mineral acid solutions in both water and in aqueous-organic solvents have been used as eluents. The retention mechanisms of these compounds on alginic acid, Rexyn 102 (Hplus) and Dowex 50-X4 (Hplus) thin layers are discussed. Interesting separations of the alkaloids were carried out on alginic acid and Rexyn 102 (Hplus).     

Acid modified diatomaceous earth--a sorbent material for thin layer chromatography

Natural diatomaceous earth (DE) is modified by flux calcination and refluxing with acid. To characterize natural DE, modified DE's [flux calcinated (FC)DE and FCDE-I] and silica gel 60GF(254) (Si-60GF(254)) are analyzed microscopically, physically, and chemically by various techniques. FCDE-I and Si-60GF(254) are investigated for their usefulness in the stationary phase of thin layer chromatography (TLC) both individually and in composition. Sodium diethyldithiocarbamate (DEDTC) and ammonium pyrrolidinedithiocarbamate (PyDTC) are prepared as Co or Cu (M) complexes [M(DEDTC)(2) and M(PyDTC)(2), respectively]. These complexes and their mixtures are run on thin layers of Si-60GF(254) and FCDE-I individually, and on various FCDE-I and Si-60GF(254) mixtures. Pure toluene and various toluene-cyclohexane mixtures (3:1, 1:1, 1:2, 1:3, v/v) are used as mobile phases for the running the complexes. The best analytical separations of both M(DEDTC)(2) and M(PyDTC)(2) complexes are obtained when using pure toluene and toluene-cyclohexane (3:1, 1:1, v/v) as mobile phases on FCDE-I-Si-60GF(254) (1:3, 1:1, w/w) layers as stationary phases. This study shows that it is possible to qualitatively analyze and to satisfactorily separate a mixture Cu(2+) and Co(2+) cations on cited chromatographic systems.     

The amino acid ratio on thin layer chromatography

A procedure for the use of the amino acid ratio on thin layer chromatography is described. Its use in developing countries is emphasized. The advantages of the amino acid ratio on thin layer chromatography versus paper chromatography are presented.     

Synthesis, growth, crystal structure and characterization of a new organic material: glycine glutaric acid

Glycine glutaric acid, a new organic compound has been synthesized and good quality single crystals were grown by slow evaporation technique. The structure of the grown crystal was elucidated by using single crystal XRD. The presence of the functional groups was confirmed by using FT-IR spectroscopy. The optical transparency was studied by using UV-vis spectrophotometer and it was found that the crystal is having high optical transparency. The thermal stability of the crystal was studied by using thermo-gravimetric and differential thermal analyses and found that it is stable up to 150°C. The room temperature dielectric studies were also carried out over the wide frequency range: 10 mHz to 10 MHz.     

Determination of chlorophenoxy acid herbicides by densitometry on thin layer chromatograms

A quantitative in situ t.l.c. method for the determination of chlorophenoxy acid herbicides and their salts in waters is described. The detection limit (1 ppb) is similar to that obtainable by gas chromatography, but no derivatization is needed. Silica gel G plates are pre-impregnated with a sensitized silver nitrate reagent, and the spots are scanned with a densitometer after u.v. irradiation. Linear calibration graphs were obtained in the range 100–1000 ng for most of the herbicides studied. Preliminary cleanup methods are discussed.     

Silicene,a promising new 2D material

Silicene is emerging as a two-dimensional material with very attractive electronic properties for a wide range of applications; it is a particularly promising material for nano-electronics in silicon-based technology. Over the last decade, the existence and stability of silicene has been the subject of much debate. Theoretical studies were the first to predict a puckered honeycomb structure with electronic properties resembling those of graphene. Though these studies were for free-standing silicene, experimental fabrication of silicene has been achieved so far only through epitaxial growth on crystalline surfaces. Indeed, it was only in 2010 that researchers presented the first experimental evidence of the formation of silicene on Ag(1 1 0) and Ag(1 1 1), which has launched silicene in a similar way to graphene. This very active field has naturally led to the recent growth of silicene on Ir(1 1 1), ZrB₂(0 0 0 1) and Au(1 1 0) substrates. However, the electronic properties of epitaxially grown silicene on metal surfaces are influenced by the strong silicene–metal interactions. This has prompted experimental studies of the growth of multi-layer silicene, though the nature of its “silicene” structure remains questionable. Of course, like graphene, synthesizing free-standing silicene represents the ultimate challenge. A first step towards this has been reported recently through chemical exfoliation from calcium disilicide (CaSi₂). In this review, we discuss the experimental and theoretical studies of silicene performed to date. Special attention is given to different experimental studies of the electronic properties of silicene on metal substrates. New avenues for the growth of silicene on other substrates with different chemical characteristics are presented along with foreseeable applications such as nano-devices and novel batteries.     

薄层扫描快速检测发酵液中琥珀酸

基于CuSO4与发酵液中琥珀酸的显色反应,在硅胶板上不经层析展开使用薄层扫描定量分析琥珀酸含量.在0～12 g/L范围内,测定波长680 nm,参比波长500 nm条件下,琥珀酸浓度与显色斑吸光度呈良好线性关系.方法检出限(3 S/k)为0.028 mg/L,回收率94.80％～96.12％,相对标准偏差≤3.5％(n...     

Polyimidines,a new class of polymers. I. Phenylated polypyromellitimidines

Model compounds and polymers containing the imidine functional group have been synthesized from diphenylphthalide and tetraphenylpyromellitide by condensation with mono- and diamines. The diamine monomers included: 1,6-diaminohexane, p-phenylenediamine, and 4,4′-diaminodiphenyl ether. Reactions were run either in biphenyl or with no solvent at 250–300°C to yield up to 57% product with molecular weights up to approximately 16,000 and inherent viscosities to 0.15. All polymers were soluble in chloroform and dimethylformamide and showed thermal stabilities by TGA to range from 225°C (for aliphatic backbones) to 400°C (for aromatic systems).     

Mobility of trace elements in soils by thin layer chromatography - Part I

Summary Mobility of some trace elements in a soil under different conditions of leaching has been measured in terms of R_F values with the help of the thin layer method of chromatography. While the iron ions were immobile in a soil of pH 8.8, the mobility of other trace elements was also seriously affected by the presence of Na₂CO₃. Appreciable changes also occurred in the R_F values of the trace elements with the change in the nature and concentration of other leachates. Further the removal of organic matter from the soil resulted in an increase in the movement of the trace elements.

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Zusammenfassung Es wurde die Beweglichkeit von Spurenelementen in Böden gemessen und durch die R_F-Werte mit Hilfe der Dünnschichtchromatographie charakterisiert. Eisen wird bei einem pH von 8,8 unbeweglich. Auch andere Spurenelemente sind im alkalischen Bereich wenig beweglich. Die Entfernung organischer Komponenten aus dem Boden erhöht die Beweglichkeit.

     

Synthetic diamond, a new electrode material for electroanalysis

Depending on the doping level, diamond exhibits properties of either a semiconductor or a semimetal. Heavily doped “metallic” diamond was found to be a corrosion-resistant electrode, suitable for electrochemical syntheses and analyses. The advantages of synthetic diamond in electroanalytical chemistry are its corrosion resistance, good reproducibility of electrochemical properties, low background currents, and selectivity to a number of reactions used to develop electroanalytical methods. Presented at the V All-Russian Conference with the Participation of CIS Countries on Electrochemical Methods of Analysis (EMA-99), Moscow, December 6–8, 1999.