HPLC Analysis of Nonionic Sufactants. V. Ethoxylated Fatty Acids

Abstract

High performance liquid chromatography technique was used in order to achieve separation and identification of product composition of nonionic surfactants of ethoxylated fatty acids.

Lichrosorb SI-60 (10μm) column, under gradient elution of mixture of isopropanol, methanol and n-hexane (50°C) and UV detector at 220 nm, were used for best separation of ethylene oxide (EO) adducts of fatty acids consisting of up to 20 EO units.

No derivatization of the compounds was needed. An improved baseline, in spite of gradient elution, was achieved by adding negligible amounts of anthracene to the eluents.

Brominated ethoxylated fatty acids resulting from addition of bromine to the double bond of the hydrophobic chain were also separated without a need for change in elution conditions or derivatization.     

Separation of Alkaloids Extracted from Stephania Tetranda S. Moore by Analytical High-Speed Countercurrent Chromatography

Abstract

High-Speed countercurrent chromatography is a recently developed separation method which has been remarkably improved in both partition efficiency and separation time. In the present study, this advanced countercurrent chromatographic method was applied to separation of sample mixture containing tetrandrine, fangchinoline, and cyclanoline originally extracted from

Stephania tetrandra S. Moore. Separations were performed with a two-phase solvent system composed of n-hexane/ethyl acetate/methanol/water in two different elution modes. Sample mixture containing 3 mg of alkaloids was efficiently separated in 100 min. The peak fraction of each component was analyzed with a mass spectrometer for structure identification.     

Application of Flow Programming in the Analysis of Drugs and Their Metabolites in Biological Fluids

Abstract

An HPLC procedure using flow programming under isocratic elution conditions for determination of drugs and their metabolites in biological fluids is discussed. This technique was used in the analysis of triamterene and its metabolites in urine, chlorothiazide in plasma and hydrochlorothiazide in urine. Advantages of flow programming over conventional procedures such as isocratic elution and gradient elution are discussed.     

Fractionation and Size Distribution of Water Soluble Polymers by Flow Field-Flow Fractionation

Abstract

Flow field-flow fractionation (flow FFF) is introduced as a chromatographic-like method with a potential for separating and characterizing water soluble polymers. The theory of the method is summarized, showing that one gets a size distribution curve based on the Stokes diameter, d. Problems in interpreting the elution profile in both flow FFF and gel permeation chromatography are discussed in the light of complications arising from electrostatic chain expansion in polyelectrolytes.

The experimental approach is described using a channel of 2.00 ml volume. Sulfonated polystyrenes of three different molecular weights are separated from one another with and without added salts. The dependence of retention on sample size is shown to be least in the salt solution, indicating that this is most suitable for analytical work.

The sodium salts of polyacrylic acid are also investigated. Distinct elution profiles are noted for two of these polydisperse polymers. Size distribution curves for the 2,000,000 MW sample curves are obtained from, the elution profiles and are shown to be independent of experimental variations. Finally, fractions are collected after separation and rerun through the coloumn, showing a reasonable confirmation of the expected fractionation effect.     

Determination and Use of Cumulants of the Peak Broadening Function in Steric Exclusion Chromatography

Abstract

A procedure is developed which allows to deduce from recycle measurements the central moments and cumulants of the molecular mass distribution of polymers and the broadening function by the use of properties of statistical distributions. Results of an experimental application of the method are presented.

Equations for the calculation of true molecular mass averages from the elution curve are extended for the cases of nonlinear calibration curves and nonlinear broadening.     

Countercurrent Chromatography for Isolation of Flavonol Glycosides From Ginkgo Biloba Leaves

Abstract

A procedure which combined countercurrent chromatography with gradient elution and preparative high-performance liquid chromatography was developed for the isolation and the purification of the seven predominant flavonol glycosides from Ginkgo biloba leaves.     

Separation of the α-Tocopherol Model Compound 2,2,5,7,8-Pentamethyl-6-Chromanol from its Oxidation Products by High Performance Liquid Chromatography

Abstract

A rapid method is described for the separation of the α-tocopherol model compound, 2,2,5,7,8-pentamethyl-6-chromanol (6), from 9 of its oxidation products in a single 35 minute run. Separated derivatives of 6, in order of elution, included the 5-cholesteroxymethyl (1), spirotrimer (2), spirodimer (3), 5-formyl (4), 5-ethoxymethyl (5), dihydroxydimer (7), chroman dione (8), quinone (9) and pyrano xanthene (10). A normal phase system, using gradient elution is employed, the eluent being monitored at 290 nm. The minimum detection limit for compounds 1–8 was 0.1 μg per injection and for compounds 9 and 10 it was 0.3 μg per injection.     

Atypic Gel Permeation Chromatography of Alcohols

Abstract

The elution behaviour of alcohols in the systems Bio Beads SX-8/dichloromethane and Sephadex LH-20/dichloromethane is investigated. On Bio Beads SX-8 the elution volumes are lower than expected for normal GPC behaviour, which is perhaps due to hydrogen bonding in solution. On Sephadex LH-20 adsorption takes place by means of hydrogen bonding, which can be used for very selective separations.     

Solid Phase Oxidation of Alcohols and Benzyl Halides to Carbonyls Using Bromate Exchange Resin

Abstract

Aromate exchange resin prepared by a simple elution technique and used for the biphasic oxidation of alcohols and benzyi halides to corresponding carbonyl compounds.     

Isolation by Means of Preparative Reversed-Phase Liquid Chromatography of Epimeric Alcohols Formed Upon Reduction of Pregnenolone and Progesterone

Abstract

A method is described which permits complete separation on a preparatory scale of the 20R and 20S epimeric alcohols obtained from lithium aluminium hydride and sodium borohydride reduction of pregnenolone and progesterone, respectively. The retention behaviour and resolution obtained on chromatography of the epimers on C-18 bonded phase material and elution with different acetonitrile/water and methanol/water mobile phases were studied. The order of retention is in both cases in accordance with ¹H-NMR chemical shift data which indicate a stable conformation with a more exposed 20-OH group in the 20S (=20α) epimer. Deviations from the elution order expected for true reversed-phase retention mechanisms were found on elution with mobile phase systems of reduced water content.     

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.     

Ion-Exchange Preconcentration and Separation of Trace mounts of Platinum and Palladium

ABSTRACT

The preconcentration and separation of platinum and palladium from weakly acidic solution (pH=4) were done on microcolumn packed with Cellex-T resin. Selective platinum elution from the column was performed with 0.01 mol/l glycine solution at pH=12, while for palladium elution 1.2 mol/l thiourea (pH=0.5) or 4.0 mol/l potassium thiocyanate (pH=1) may be used. As the detection technique was used either FAAS or GFAAS, depending on the concentration of studied metals in the eluate.     

Micropreparative TLC Separation of Large Sample Volumes. Frontal + Elution Chromatography

Abstract

It is demonstrated that mixtures containing few compounds can be applied as wide zones on the edge of the thin layer using a sandwich tank with glass distributor. The mixture is partially separated during application (frontal chromatography) so that subsequent elution accomplishes complete separation. Using 5 × 20 cm plates of silica, 0.5 mm thick, 1 - 3 ml samples were separated easily which permitted elution of 3 - 9 of separated compounds from a single plate.     

Analysis of Lipid Classes by HPLC with the Evaporative Light Scattering Detector

Abstract

The evaporative light scattering detector enables the detection and quantitation of all relatively non-volatile lipids. The mixtures of polar and non-polar lipids were separated in one run, in 20 to 25 minutes on Silica Si-100 columns, using consecutive gradients of pentane to diethylether, to chloroform, to methanol containing a large concentration of ammonia.

The flexibility of the method is illustrated by the change in elution patterns following the treatment of the packing material by ammonia. For example, the elution order of phosphatidyl inositol and phosphatidyl choline is reversed and the separation of the former compound from phosphatidyl serine, which is generally difficult, is now accomplished readily.

The weak dependence of the detector sensitivity on the nature of the analytes permits an easy quantitation, as illustrated by the results of the analyses of lipid classes in blood serum, amniotic fluid, beef brain and other natural samples.

The method is particularly useful for the analysis of lecithin and sphingomyelin in the amniotic fluid. The ratio of the concentration of these two compounds is an indicator of lung maturity and could permit an early diagnosis of the respiratory stress syndrome of neonates.     

Evaluation of Alkaline Earth and Transition Metals for Use in the Ion Moderated Partition Chromatography of Sugars

Abstract

The elution behavior of 28 sugars and related compounds from high performance chromatography columns packed with alkaline earth and transition metals was investigated. As expected from the well-known chromatography of the commercially available calcium, silver, and lead form columns, elution behavior is highly metal-ion form specific. A significant data base of sugar elution versus column cationic-form was generated to permit the selection of new columns to enhance the separation of specific eluting species. Sugars resulting from the hydrolysis of wood were closely examined. Arabinose and galactose, known to be difficult to separate on commercially available lead and silver-form columns, were well separated on custom-packed rubidium and cesium-form columns.     

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.     

A Simple Method to Optimize Elution from Affinity Chromatography

Abstract

A rapid and convenient screening method to optimize elution from affinity chromatography is described. An immunoaffinity system employing antibody bound human thyroglobulin (hTg) served as a model. Anti - hTg was complexed to polystyrene microplates adsorbed hTg. Immune complex (IC) dissociation and elution of antigen by various agents was determined by enzyme linked immunosorbent assay (ELISA). The method permits simul taneous monitoring of residual antigenicity and of possible desorption of antigen from its solid support.     

Separation of Pd(II) and Tl (III) from Various Metal Ions on Hydrous Zirconium Oxide Column

Abstract

The utility of hydrous zirconium oxide for the separation of metal ions has been explored. The Kd-values from different concentrations of chloride ions(pH-2) have been determined. On the basis of the sorption data Pd (II) and Tl (III) have been quantitatively separated from a number of metal ions. The representative elution curves are given and the recovery of the metal ions is reported.     

Experimental Study of Model Bonded Stationary Phases for Liquid Chromatography II. Silica/Polystyrene

Abstract

Mechanisms of separations performed on bonded phases in liquid chromatography are investigated by studying model grafted phases.

These phases are prepared by reaction of chlorinated silica with living anionic polystyrene of various molecular weights. Owing to thermodynamic predictions, an expression of the elution volume of various solutes on such packings and conditions for reverse-phase chromatography are proposed.