The Role of Spacers in Displacement Thin-Layer Chromatography

Abstract

Displacement chromatography generates highly concentrated bands which migrate closely to each other along the stationary phase bed.

Spacer-displacement thin-layer chromatography is a planar method improving the observable resolution by inserting odd compounds (spacers) among the members of displacement train to be separated.

Substances were chromatographed by displacement mode of development using silica plates, chloroform carrier and triethanolamine displacer.

Resolution formula valid for elution chromatography has been adapted to the displacement type of developments. Explanation for the numerical value of required separation is given for various cases of displacement thin-layer chromatography.

Equations are suggested in order to calculate yield, loss and efficiency of displacement chromatography.     

Separation and Identification of Certain Organophosphorous Pesticides Residues in Vegetable

Abstract

A rapid and sensitive method using impregnated thin layer chromatography (TLC) for detection and estimation of organophosphorous pesticides residues from vegetable has been developed. Compared to ordinary thin layer chromatography this method is faster more sensitive and accurate. The correlation with the Impregnant (p-cresol) and the pesticides have been determined by Infrared Spectroscopy.     

High Performance Thin-Film Chromatography in Biological Studies

Abstract

The conventional thin-layer chromatography/TLC/ method of Egon Stahl had not been significantly modified for a long time. But lately much attention was paid to the optimization of the rapidity and sensitivity of the method. The advances in column, gas and liquid chromatography very much contributed to ic. In TLC, like in column chromatography, the use of very fine and homogeneous sorbent fractions was very promising. It appeared especially efficient in liquid chromatography where diffusion coefficients are low.     

Flash Pyrolysis-Gas Chromatography Using an Internal Standard For Quantitative Determination Of Resin Content in A Model Thermosetting Composite System

Abstract

It has been demonstrated, by operation on a series of thermosetting phenolic-asbestos composites, that pyrolysis gas chromatography may be applied as a general method for estimating polymer content in cured composite materials. A platinum filament is employed for flash pyrolysis and quantitative estimation is based on the internal standard method.     

Applicability of an HPLC System in the Analysis of Biodegraded Crude Oil Components

Abstract

High performance liquid chromatography has been used for the separation of biodegraded crude blend into fractions using back flushing procedure. The stationary phase was Energy analysis (3.9mm × 30cm) NH₂ column and the detection mode was UV absorptiometry. The method was compared with the liquid chromatography method.     

A Combined Thin-Layer Chromatography/Micro Infrared Method

Abstract

A method is described for the automatic elution of chromatographed compounds on thin-layer chromatography plates and their subsequent identification by micro infrared spectroscopy.

The method is simple, easy to perform in a few minutes, and requires 5 μg of material, 3 mg of KBr powder, and 150 μl of solvent.     

Gas Chromatographic Analysis of Aminothiol Radioprotective Compounds

Abstract

A gas chromatographic method is described for aminothiols and disulfides. This method is based upon the formation of the trimethysilyl derivatives and their separation by gas chromatography. The kinetics of the derivative formation were investigated. A synthetic method for C4 to C6 aminothiols is given.     

Simultaneous Measurement of Adenosine 5′-Triphosphate and its Degradation Products by Reverse-Phase Ion-Pair Chromatography

Abstract

A method is presented for the simultaneous measurement of adenosine 5′-triphosphate and its uv-absorbing degradation products by reversed-phase liquid chromatography using tetra-butylammonium phosphate as an ion-pair agent. The method is suitable for the measurement of these compounds in isolated smooth muscle.     

The Quantitative Separation of Alkyl and Phenethyl Halides by HPLC

Abstract

A method is described for the quantitative separation of alkyl and phenethyl halides in mixtures containing benzene or toluene. This method involves the isocratic chromatography separation of the mixture, using a ODS column and the detection of the compounds by means of a RI detector.     

Technique for In Situ Coating of Ag+ Onto Silica Gel in HPLC Columns for the Separation of Geometrical Isomers

Abstract

A method is described for the in situ coating of silver nitrate onto silica gel in high performance liquid chromatography columns. The columns effectively separated a series of geometrical isomers.     

Rapid Determination of Propranolol and 4-Hydroxypropranolol in Plasma by High Pressure Liquid Chromatography

Abstract

The resolving power of high pressure liquid chromatography has been combined with the sensitivity of fluorescence detection to develop a method for the determination of propranolol and 4-hydroxypropranolol in plasma. A single selective extraction step precedes chromatography on a high efficiency bonded phase column. The limits of quantitation are approximately 2 ng/ml of plasma for each drug. The analysis of a number of clinical samples has demonstrated the application of the method in pharmacokinetic studies, but the possible interference of other drugs and their metabolites is still under investigation.     

A CONVENIENT SYNTHESIS OF DIMETHYLPHOSPHINYL ACETIC ACID

Abstract

A method is presented for preparing dimethylphosphinyl acetic acid by carboxylation of trimethylphosphine oxide α-carbanion. The product from this simple one step reaction is easily purified by extraction and ion exchange chromatography.     

Assessment of ethanol and acetonitrile in 18F-FDG preparations by means of liquid chromatography

Introduction Acetonitrile (ACN) and ethanol (EtOH) are common solvents used in radiopharmaceutical production. In accordance to official compendia, the concentration of these solvents should be assessed by gas chromatography. In the present paper, an optimized method, based on Koziorowski (2010), is validated. Methods ACN and EtOH concentrations and retention times (Rt) were obtained by a HPLC system equipped with a refractive index detector (RID), an ion exclusion column and ultrapure water as mobile phase. The methodology was validated following the ICH Q2(R1) requirements. Results The solvents EtOH and ACN were eluted at 23.22 and 26.32 minutes, respectively, with a final run time of 30 minutes. The validation parameters (accuracy, precision, linearity, specificity, robustness, detection and quantification limits) were obtained. Conclusions A reproducible HPLC method for the quantification of residual solvents in preparations of 2-deoxy-2-[fluorine-18]fluoro-D-glucose (¹⁸F-FDG) was described and validated. The method was precise, accurate, selective, robust and linear over a wide range. In addition, this method showed a high sensitivity, with limits of detection and quantitation comparable to the usual methods by gas chromatography.     

Improved High-Pressure Liquid Chromatographic Assay of Serum 25-Hydroxycholecalciferol and 25-Hydroxyergocalciferol After Reverse-Phase Sep-Pak C18 Cartridge Preparation of Sample

Abstract

A simplified method is described for extracting and purifying 25-hydroxycholecalciferol and 25-hydroxyergocalciferol from serum for quantitation by high-pressure liquid chromatography. The method involves extracting and purifying these metabolites from serum (1–10 ml) with a reverse-phase octadecylsilane bonded silica cartridge (Sep-Pak C₁₈). This method is faster than a previously described method involving extraction with dichloromethane and purification by Sephadex LH-20 chromatography. The correlation between the two methods was excellent (r² = 0.96, p≤0.0001). The coefficient of variation for the new method is 4.3%. The new method allows measurement of 25-hydroxyergocalciferol from human serum since both 25-hydroxycholecalciferol and 25-hydroxyergocalciferol are extracted equally. This allows the use of [³H] 25-hydroxycholecalciferol to monitor the recovery of both the D₂ and the D₃ forms of the metabolite.     

Reverse Phase Isolation of Pyrrolizidine Alkaloids

Abstract

A new liquid chromatography method for the isolation of pyrrolizidine alkaloids has been developed. The use of reverse phase high pressure liquid chromatography with a methanol - .01 M KH₂ PO₄ (pH 6.3) solvent system is discussed. Pyrrolizidine alkaloids from Senecio vulgaris, S. longilobus, and S. jacobaea have been isolated and identified.     

Quantitative Analysis of the Molecular Weight Distribution of Inulin by Means of Anion Exchange HPLC with Pulsed Amperometric Detection

Abstract

A method, using anion exchange chromatography and pulsed amperometric detection, is described for quantitative analysis of the oligosaccharides present in inulin. The analysis of a number averaged and molecular weight averaged degree of polymerisation and the dispersion of inulin and inulin fractions is given.     

An Improved Analysis of the Pheromone 3-Methyl-2-Cyclohexen-1-One in a Controlled Release Formulation by Using Liquid Chromatography

Abstract

A method was developed for estimating the quantity of the pheromone 3-methyl-2-cyclohexen-1-one in a controlled release formulation. The thermal method measured the amount of releasable pheromone remaining in the formulation by using liquid chromatography with a variable wavelength ultraviolet detector. This method is 150 to 250 times more sensitive than the liquid chromatographic method used previously.     

High Performance Liquid Chromatographic Method for Prostaglandin E2 Determination in Human Gastric Juice Without Derivatization

Abstract

A rapid and practical method for the separation and quantitation of PGE² in human gastric juice by high performance liquid chromatography is described. Separation on a reversed-phase column and UV detection allows quantities as little as 20 nanograms of PGE² to be detected. Specificity, sensitivity, high yield and reproducibility make this method particularly suitable for prostaglandin determination in human gastric juice.     

Purification of an Endogenous Modulator for Voltage-Sensitive Calcium Channels Using the Eccentric Multi-Layer Coil Planet Centrifuge

Abstract

High-speed countercurrent chromatography using a two-phase solvent system was found to be the method of choice for purifying an endogenous Ca2+ channel modulator. The solvent system composed of n-butanol, acetic acid and water (4:1:5) was most suitable for resolving the active material from other unknown substances of low molecular weight. Countercurrent chromatography proved useful in validating the presence in rat brain of an endogenous ligand for dihydropyridine-sensitive Ca²⁺ channels. Moreover, the degree of purity of the active material obtained by countercurrent chromatography is suitable for consecutive analysis by mass spectrometry or nuclear magnetic resonance.     

Preparative Isolation of Pyrrolizidine Alkaloids Derived from Senecio Vulgaris

Abstract

A large scale method for the isolation of pyrrolizidine alkaloids has been adapted from a previously published analytical method. This method is a reverse phase high pressure liquid chromatography technique, utilizing a .005 M KH₂ PO₄ (pH 6.3) — methanol solvent system. The pyrrolizidine alkaloids derived from Senecio vulgaris (common groundsel) have been utilized in this system.