Some New Developments in Centrifugal Partiton Chromatography and Applications in the Separation of Natural Products

Abstract

A two-pump method for the control of stationary to mobile phase ratios in a cartridge centrifugal partition chromatography system is described. This cartridge CPC set-up and a rotating coil instrument are used in the separation of natural products from complex mixtures contained in crude plant extracts.     

Analysis of Mixtures by Ion Kinetic Energy Spectrometry

Abstract

A mass spectrometric method in which separation and compound identification are accomplished in a mass-analyzed ion kinetic energy spectrometer (MIKES) is described. This procedure is possible in a reversed sector (source-magnet-energy analyzer-detector) mass spectrometer when ions characteristic of each mixture component are caused to fragment after mass analysis. For each mass-selected ion, a scan of the ion kinetic energy spectrum identifies the daughter ions arising from unimolecular and/or collision-induced dissociations. Straightforward application of this method to isomeric C₅H₁₀0 ketone mixtures allows separation, identification, and quantitative analysis which is easy, rapid, and unambiguous.     

Development of High Pressure Liquid Chromatography (HPLC) for Fractionation and Fingerprinting of Petroporphyrin Mixtures

Abstract

A method is described which permits the analysis of fossil porphyrin mixtures by HPLC. This method involves the fractionation of the demetallated petroporphyrin mixtures on silica columns followed by rechromatography of the trapped fractions on ODS columns. This coupling of the two modes of HPLC provides a fast and effective method for the separation of isomeric porphyrins and for the petroporphyrin fingerprinting of geological (oil/shale) samples. Representative examples of analysis are discussed in terms of the potential applicability of the technique in the areas of structure elucidation and geochemical correlations.     

A Low Cost Gas Sampling Valve and Gc Set-Up for Analysis of Low Concentration Gas Mixtures

Abstract

A gas sampling valve suitable for on-line injection of low pressure (< 0.5 torr) gas mixtures is described. Its advantages over the commercially available valves are enumerated. An error of < 3 per cent due to non-reproducibility in sample injection was observed. A simple arrangement of column and hot wire detector together with this valve enabled quantitative separation of CO and O₂ with a lower limit of ～ 1 × 10^?7 moles for each component.     

Influence of Bonded-Phase Column Type,Mobile Phase Composition,Temperature and Flow-Rate in the Analysis of Triglycerides by Reverse-Phase High Performance Liquid Chromatography

Abstract

Two chromatographic systems for RP-HPLC analysis of triglycerides, operating under isocratic conditions using octadecylsilane and octylisilane bonded phases, are described.

The influence of such chromatographic factors as bonded phase column type, mobile phase composition, temperature and flow rate on retention, analysis selectivity and efficiency, and separation of mixtures of homogeneous triglycerides was assessed. Linear relationships were established for the logarithm of the capacity factor and selectivity for each triglyceride in relation to temperature, the proportion of certain mobile phase components and flow rate.

The octadecylsilane bonded phase was more selective when analyzing triglycerides with a partition number below 48, while octylsilane was appropiate for separating mixtures of long chain saturated triglycerides to the detriment of the resolution of triglycerides with low partition numbers. ACN/ACE/THF (58/38/4) was a suitable mobile phase for use with the octadecylsilane bonded phase, and ACN/THF /H₂O (60/40/1) for the octylsilane bonded phase. A column temperature of 30°C and a flow rate of 1.5 mL/min resulted in acceptable resolution and analysis time in both systems.     

A Novel Approach to Reversed-Phase Preparative High-Performance Liquid Chromatography of Peptides

Abstract

In this study, we describe a novel approach to preparative liquid chromatography which takes advantage of the different relative hydrophobicities of components of a sample mixture, so that when a column is optimally loaded with an aqueous solution of the sample mixture, there is competition among the sample components for the adsorption sites on the hydrophobic stationary phase. The more hydrophobic components compete more successfully for these sites than more hydrophilic components, which are displaced and immediately eluted from the column. Thus, the major separation takes place in water. Subsequent treatment with an aqueous organic modifier is only required to wash retained components off the column and takes no part in the major separation process. This approach was applied to the preparative purification of mixtures of closely-related peptides, representing the crude peptide mixtures typically obtained from solid-phase peptide synthesis. The excellent separation profiles and high yields of pure peptide products on analytical columns reported in this study demonstrate that this methodology has great potential for preparative separation of a major component from hydrophilic and/or hydrophobic impurities.     

SEPARATION OF SOME AROMATIC CARBONYL COMPOUNDS BY THIN LAYER CHROMATOGRAPHY OF THEIR ISONICOTINOYL HYDRAZONE DERIVATIVES

Abstract

The separation of 13 isonicotinoyl hydrazones derived from some isomeric aromatic carbonyl compounds by thin layer chromatography is described. Methods for separating and identifying the components of complex mixtures of these hydrazones are discussed.     

Triethylamine Formate Buffer for HPLC-field Desorption Mass Spectrometry of Oligopeptides

Abstract

A triethylamine-formate buffer system for the HPLC analysis of mixtures of oligopeptides is described. The volatility of TEAF facilitates buffer removal for subsequent field desorption-mass spectral qualitative and quantitative analyses. TEAF permits femtomole quantification of somatostatin, is UV transparent and enables high resolution separation of oligopeptide mixtures.     

A computational,X-ray crystallographic and thermal stability analysis of TETROL and its pyridine and methylpyridine inclusion complexes

The identification and application of (+)-(2R,3R)-1,1,4,4-tetraphenylbutane-1,2,3,4-tetrol (TETROL) as an efficient and selective host compound is described. Computational and single crystal X-ray diffraction analyses revealed that the butane backbone of TETROL adopts a relatively rigid anti-conformation, with the hydroxy groups oriented syn and connected through a cyclic, homodromic arrangement of their O–H bonds. This structure is stabilised through a pair of 1,3-hydrogen bonding interactions. TETROL forms inclusion complexes with pyridine and 3- and 4-methylpyridine, and does so selectively from mixtures of the pyridines. X-ray diffraction (single crystal and powder) and thermal analyses of the inclusion compounds are described.     

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.     

A new host compound for the selective inclusion of ethanol

A new host compound of the onium salt type,N-(3-biphenylmethyl)quininium bromide (1), is described. This host compound shows an unusually high selectivity for the inclusion of ethanol. Using this clathrand, ethanol can be extracted from a variety of solvent mixtures. In most cases, a remarkable enrichment of the ethanol is observed. The following solvents in a mixture with ethanol remain in the mother liquid: methanol,n-propanol,n-hexane, pyridine.     

Pseudophase Liquid Chromatography: Applications to TLC

Abstract

The technique of pseudophase liquid chromatography is described. In this type of separation, a substance does not partition to the bulk mobile phase but rather to discreet aggregates or other substances (i.e., micelles or cyclodextrins) which are dissolved in the mobile phase. Advantages of this technique include high selectivity, low cost, and low volatility and toxicity of the mobile phase. Appropriate previous TLC separations are reviewed and new data on the separation of quinones are presented.     

Studies of Hydrous Zirconium Oxide. I. Thin-Layer Chromatography of Some Metal Ions on Hydrous Zirconium Oxide: Quantitative Separation of Bi(III) from Several other Metal Ions

Abstract

The analytical potentiality of hydrous zirconium oxide as an ionexchanger has been investigated by thin-layer chromatographic (TLC technique. Binder-free thin-layers of hydrous zirconium oxide are useful for 25 ternary and 12 quaternary separations. Quantitative separation of Bi (III) from some ternary and quaternary mixtures of metal ions has been achieved.     

The Purification of Xanthene Dyes by Reverse Phase High Performance Liquid Chromatography

Abstract

A reliable method for the separation of fluorescein dyes from their impurities was developed using high performance liquid chromatography and involved a μBondapak C₁₈ reverse phase column and mixtures of methanol and ammonium acetate buffer. This technique was used to verify the purity of commercial products as well as to aid in the development of an empirical theory related to retention of halogenated fluorescein dyes by reverse phase columns.     

A Method of Self Calibration for Molecular Weight Distribution Determinations for Liquid Crystalline Polymers

Abstract

A method of molecular weight calibration was devised for various substituted liquid crystalline polymers with substantial molecular weight repeat units. With the use of gel permeation chromatography, oligomer peak separation was achieved offering a method for self calibration for molecular weight distribution determinations. Employing an overlay of a low molecular weight polystyrene standard, a retention time marker was utilized as a source from which to mark an oligomer peak. The calibration plot produced using this technique showed much better correlation coefficients than that of the polystyrene calibration plot. In addition, molecular weight determinations made from the two techniques yielded two distinct molecular weight averages and distributions, indicating polystyrene to be a poor relative calibration method for the liquid crystalline polymers tested. The technique illustrates the utility of alternative calibration methods when samples show certain physical characteristics.     

Solvent Extraction Separation of Zirconium (iv) With Anberlite LA - 1 From Citrate Solutions

Abstract

Zirconium was quantitatively extracted with 8 × 10^?2 M of Amberlite LA-1 or LA-2 xylene from 0.001 M citric acid at pH 3.5 and it was stripped from the organic phase with 2 M hydrochloric acid and was determined spectrophotometrically at 665 nm as its complex with arsenazo III. Zirconium was separated from binary as well as tertiary mixtures by exploiting the difference in the distribution coefficient or by selective extraction or selective stripping. The method was applied for the analysis of zircon.

Zirconium was extracted as its anionic complex with various mineral acids by liquid anion exchanger. The chlorocomplex of zirconium was extracted from 6–10 M hydrochloric acid with trioctylamine^1–5, triisooctylamine⁶ or Aliquat 3365⁷. The sulphotocomplex of zirconium was extracted with Aliquat 3365⁸, Primine JMT⁹, Alamine 336¹⁰. The nitratocomplex was less extensively utilised for the extractive separation of zirconium^{11, 12}.

Zirconium was extracted quantitatively from oxalate^{13, 14} and malonate media¹⁵. These extractions were carried out at low pH and separated zirconium from large number of associated elements. The ion exchange chromatographic behaviour of zirconium on column with cation exchange^16–17 or with anion exchange¹⁸ resin with citric acid as eluent were utilised but extraction studies from citrate solutions were never attempted.

From the critical study of existing methods it was observed that zirconium was extracted at narrow pH range; with high concentration of complexing ligand for extraction with liquid anion exchangers and long period of equilibration for extraction as well as stripping. So also such extractions were possible mostly at milligram concentrations involving use of hazardous diluents like benzene. In order to circumvent these difficulties an attempt was made to develop a better method for the solvent extraction separation of zirconium by ion pair formation.

Therefore this paper presents systematic investigations on the solvent extraction separation of zirconium from citrate media with liquid anion exchangers. From the study of various factors. The optimum conditions for the extraction and the separation of zirconium from associated elements are evaluated. The method has been extended for the analysis of zirconium from zircon.     

Studies on Hydrated Stannic Oxide. Part VI. Thin-Layer Chromatography of Some Anions on Hydrated Stannic Oxide: Quantitative Separation of Cr(VI) from Some Ores and Alloys

Abstract

The analytical applications of hydrated stannic oxide as an ion-exchanger have been investigated by thin-layer chromatographic (TLC) technique. Binder-free thin-layers of hydrated stannic oxide are useful for some binary separations. Quantitative separation of Cr(VI) and Mo(VI) from some binary mixtures have been achieved. The method is applied to separate microgram-quantities of Cr(VI) quantitatively from several ores and alloys in ammonia buffer (pH 10) system.     

Thin Layer Chromatographic Separation of Closely Related Dyes

Abstract

A scheme for the TLC separation of twenty five dyes on silica-gel-zinc acetate impregnated plates using a mixture of n-butanol-benzene-ethylacetate as developing system is described. Examples of separations of dyes in mixtures are reported.     

Simultaneous Determination of Polycyclic Aromatic Hydrocarbons by Variable Angle Spectrofluorimetry

Abstract

The use of variable-angle fluorescence spectra together with multilinear curve-fitting techniques for the resolution of mixtures of polycyclic aromatic hydrocarbons (PAHs), is described. Only one spectrum is necessary to determine four compounds in a mixture even when a severe overlap occurs. The PAHs are quantified at ng/ml levels.     

Simultaneous Determination of Diazepam,Oxazepam and Temazepam in Spiked Urine By Hplc

ABSTRACT|Oxazepam and temazepam are two minor metabolites of diazepam. These three benzodiazepines may be found in presence of each other in biological fluids.

Therefore, in this study an HPLC method was developed to separate and analyze them. Benzodiazepines have ability to form inclusion complexes with p-cyclodextrin (β-CyD). According to the degree of binding constant with β-CyD, these compounds can be separated by β-CyD bound to silica (cyclobond column) as the stationary phase using HPLC.

The development and validation of the HPLC procedure for the separation and determination of these compounds in mixtures were studied. The mobile-phase system consisted of phosphate buffer (pH 7): methanol [75:25], with flow rate 0.8 ml min^?1 and UV detection at 240 nm was used.

The calibration graphs were rectilinear from 0.1-2.5 μg/ml and coefficients of variation were <2% for the three compounds in bulk forms.

The method was used to analyse these bezodiazepines in spiked urine containing all three compounds in combination. Recoveries were 97-99.8%

The limit of detection and limit of quantitation were 0.05 μg/ml and 0.1 μg/ml, respectively.

The described method is selective, rapid, simple, reproducible and accurate.