Thin Layer Chromatography of Purines on Silica Gel G Impregnated with Transition Metal Ions; Assay of Caffeine and Theophylline in Pharmaceutical Formulations

This study was undertaken to develop thin layers of silica gel G impregnated with transition metal ions for separation, identification and estimation of purines. The influence of transition metal ions and eluting solvents on chromatographic behaviour (hR_f) has been studied. The method was applied for qualitative analysis of purines in the mixtures and quantitative analysis of purine bases in the mixture as well as in pharmaceutical formulations. The results were compared statistically with those obtained by official methods. The method is simple, reproducible, and accurate within 1.3 ± 0.6%.     

Thin-Layer Chromatographic Method for Separation of Wheatgrass Pigments on Sucrose Impregnated Silica Gel Plates

JPC – Journal of Planar Chromatography – Modern TLC -     

Chromatography of Some Metal Ions on Silica Gel Thin Layers in Butanol-Formic Acid Media

Abstract

Chromato graphic behaviour of some metal ions on silica gel thin layers has been studied in butanol—formic acid media. The results have been compared with those obtained in aqueous formic acid medium. Many important and analytically difficult separations have been achieved. Some thin layer chromato graphic parameters for the separation of Vo²⁺ from numerous metal ions using 20.0 M formic acid in butanol have been determined.     

Selective Adsorption of Arsenic Ions on Silica Gel Impregnated with Ferric Hydroxide

Abstract

Selective adsorption of trace arsenite- and arsenate anions in an aqueous solution by ferric hydroxyde supported on silica gel particles was investigated. Silica gel particles were loaded with ferric hydroxide of the range of 1 – 3 wt. % in terms of Fe based on the dry gel, and the extent of adsorption of arsenite or arsenate ion measured by batch- and column processes, being the highest at pH 6 in the presence of diverse foreign ions. With the use of silica gel containing 3.3 wt. % Fe, as much as 0.07 m mol of arsenic per gram of dry gel was adsorbed.     

Interaction of Formic Acid with the Silica Gel Network

Silica gels can be made by direct reaction of formic acid with tetraethyl orthosilicate. We have characterized wet gels of this type using a beam-bending technique that yields the elastic modulus, Poisson’s ratio, viscoelastic relaxation function, and permeability. When the experiment is performed in ethyl formate, the silica network behaves in an elastic fashion; the permeability is low (<1 nm²), indicating a pore radius of <4.3 nm. The capillary pressure generated in such small pores is estimated to be sufficient to cause collapse of the pores during drying, which would account for the observed ultramicropores in this type of gel. When the pore liquid contains formic acid, viscoelastic relaxation is relatively rapid. Studies of cyclosiloxane compounds indicate that formic acid can attack only the strained siloxane bonds of the network, which would account for the relaxation behavior. Aging in formic acid causes rapid initial shrinkage, because formic acid accelerates condensation of silanols, which drives syneresis; the modulus increases and the permeability decreases monotonically, so there is no indication of coarsening during aging in formic acid, even at 70°C.     

Retention of Some Metal Ions and Their Separation on Silica Gel Modified with Acid Red 88

 Acid Red 88 is strongly extracted by chloroform solutions of Aliquat 336 by an ion exchange mechanism and for its reextraction from the ion pair formed, relatively high concentrations of mineral acids are required. By impregnation of silica with the ion pairs between the cation of Aliquat 336 and the anion of the dye a chelating sorbent for metal ions can be obtained. The sorbent prepared may be successfully used for separation of mixtures of various metal ions by the column extraction chromatography technique, additional purification of sodium and potassium salts from ions of heavy metals and for concentration of trace amounts of ions of various metals from aqueous solutions followed by their quantitative determination. The sorbent can be used repeatedly in the process of sorption and desorption of metal ions (especially those forming less stable complexes with the reagent) after regeneration with solutions of perchloric acid. Received January 28, 1998. Revision March 1, 1999.     

TLC Separation of some closely Related Synthetic dyes Impregnated Silica Gel Layers

Abstract

Ammonium molybdate and Copper sulphate were found as good impregnants for improving the separation of some closely related thirty synthetic dyes on silica gal ‘G’ layers using the solvent system BuOH-AcOH-H₂O (25:5:10). Tables are presented to illustrate the comparison in resolution of dyes on plain and impregnated silica gel layers.     

Microwave-Assisted,Rapid, Solvent-Free Aza-Michael Reaction by Perchloric Acid Impregnated on Silica Gel

Highly efficient solvent-free aza-Michael additions of a variety of amines to α,β-unsaturated carbonyl compounds under microwave-irradiation conditions catalyzed by perchloric acid impregnated on silica gel (HClO₄/SiO₂) is reported. The reactions are completed within 2–7 min in a microwave oven to produce the corresponding adducts in excellent yields, and the catalyst can be recovered and reused.     

Retention Behavior of Metal Ions on Tri-n-Butyl Phosphate and Tri-n-Butyl Amine-Impregnated Silica Gel G Layers: Quantitative Separation of Lead from Other Metal Ions and Synthetic Alloys

JPC – Journal of Planar Chromatography – Modern TLC - The retention behavior of 40 metal ions has been studied on tri-n-butyl phosphate (TBP) and tri-n-butylamine (TBA)-impregnated...     

TLC Separations of Amino Acids on Silica Gel Impregnated Layers

Abstract

Copper sulphate and polyamide were tried as impregnants for improving the separation of twenty amino acids on silica gel ‘G’ layers using a new solvent system MeOH-BuOAc-AcOH-Pyridine(20:20:10:5). Tables are presented to illustrate the improvement in resolution of amino acids on silica gel plates.     

Chromatographic Behavior of 43 Cations on Silica Gel G in Acetone-Formic Acid Systems

Abstract

A systematic study of the chromatographic behavior or 43 metal ions has been carried out in Acetone-Formic Acid systems on thin layers of Silical Gel G. The separation potential of these systems has been investigated for numerous metal ions and a number of useful and interesting separations have been predicted. The results obtained have been discussed and analysed.     

硅胶中六种金属离子反王水消解-离子色谱检测方法的研究

本文建立了硅胶中金属离子反王水消解-离子色谱检测的方法.系统研究了硅胶的最佳前处理条件,选择消解试剂为氢氟酸和反王水,还原剂为抗坏血酸,实现了Na+、Zn2+、K+、Fe2+、Mg2+和Ca2+六种金属离子基线分离.该方法简便快速、灵敏、重现性好.进一步以该方法对实际硅胶样品中微量金属离子测定,获得较好的结果.     

β-环糊精固载硅胶薄层色谱法拆分盐酸克伦特罗对映体

以羧甲基纤维素钠为交联剂,将β-环糊精固载在硅胶GF254表面上,并用其制备薄层色谱板。使用该薄层板拆分了盐酸克伦特罗对映异构体。考察了薄层拆分中展开剂的影响,发现展开剂中醇的种类和比例对拆分效果有较大的影响。分别考察了10种醇与乙腈混合溶剂作展开剂对拆分的影响,结果显示,只有正丁醇-乙腈、仲丁醇-乙腈、叔丁醇-乙腈混合溶剂作展开剂可拆分盐酸克伦特罗对映体。薄层色谱法拆分盐酸克伦特罗对映体的条件为：以1.00 g β-环糊精固载在15.00 g硅胶GF254表面上,并用其制备薄层板,以乙腈-仲丁醇(体积比为20∶80)混合溶剂作展开剂,于室温下展开。在此条件下,盐酸克伦特罗对映体单体在薄层色谱板上的比移值Rf分别为0.34和0.72,分离度Rs为4.09,实现了基线分离,而且样品在薄层色谱板上的斑点大小一致,拆分效果最好。     

Reactivity of Thioglycolic Acid Physically and Chemically Bound to Silica Gel as New Selective Solid Phase Extractors for Removal of Heavy Metal Ions From Natural Water Samples

A method is presented for the immobilization of thioglycolic acid moiety on the surface of active silica gel via a simple and direct synthetic route and based on one step reaction procedure. Two-product solid phase extractors were successfully synthesized according to physical adsorption and chemical immobilization binding techniques, phases (I) and (II), respectively. The mode of interaction between the silanol group and the thioglycolic moiety was also discussed for both phases based on the infrared analysis studies. The thermal stability properties as well as the effect of buffer solutions on the percentage hydrolysis of the two silica gel phases were examined and revealed the high stability and superiority of silica phase (II) in these respects. The evaluation of the selectivity and metal uptake properties incorporated in these two silica gel phases were also studied and discussed for a series of divalent heavy metal ions under different controlling factors. The mmol/g values were found to be higher in case of phase (I). The selective removal and extraction of some heavy metal ions, viz . Cu(II), Zn(II), and Hg(II) from natural seawater samples was successfully accomplished with the percentage recovery values for the three tested metal ions in the range of 96.5-98.4 - 0.2-0.6%. The presence of higher concentrations of Na(I), K(I), Mg(II) and Ca(II) showed insignificant role or no matrix effect on such selective extraction process due to their 0% values of removal by these silica gel phases (I) and (II).     

Thin-Layer Chromatographic Separation of DMSO Complexes of Metal Ions

Abstract

Thin layer chromatography of DMSO complexes of some metal ions in a large number of solvent systems was carried out. The specific separation of DMSO complex of Hg²⁺ from others have been achieved in ethyl acetate media. Other important separations of metal - DMSO complexes are : Ni²⁺ - Co²⁺, Ce³⁺ - La³⁺ and Zn²⁺ - Mn²⁺. Some other possible separations are also reported.     

Synthesis of Monolithic Silica Gel in Alkaline Medium

The influence exerted by the basicity and nucleophilicity of a number of organic amines on the formation of a monolithic silica gel by the organic sol-gel method was studied.     

Spectrophotomhtric Determination of Vanadium with Salicylic Acid in Formic Acid Medium

Abstract

A method is described for the spectrophotometric determination of vanadium by measuring its colored complex with salicylic acid in formic acid medium. Lambert-Beer's law is followed in the range of 2.0 - 32.0 μg V/ml of the final solution. Thirty-six ions were tested and did not interfore, at the established conditions.     

Qualitative Identification of Metal Ions in Honey by Two-Dimensional Thin-Layer Chromatography

JPC – Journal of Planar Chromatography – Modern TLC - Two-dimensional thin-layer chromatography (2D TLC) has been used as a screening method for detection of the metal ions Al3+, Cr3+,...     

高价金属离子在结晶锑酸-磺胺偶氮氯膦浸渍板上的薄层色谱研究

本文报导了一种新的薄层色谱法,研究了稀土(Ⅲ)、钛(Ⅳ)、锆(Ⅳ)、铌(Ⅴ)和铀(Ⅳ)的TLC行为,有效地分离了一系列二元及三元混合物.方法简便、快速、直观.根据实验结果,推荐了镧系元素的原子序数(Z)、离子裸半径(r°)与R_f值的经验公式.计算了在各种展开剂中曲线的截距、斜率和线性相关系数(r).     

Thin Layer Chromatography of Some Metals on Silica Gel Layers Impregnated with Phenolic Acids

Abstract

Thin layer chromatography of metals was performed on silica gel impregnated with phenolic acids. The results obtained can be used to gain a better insight into the behaviour of metals under the proposed chromatographic conditions and as an additional system for their separation.