Influence of selected mobile phase properties on the TLC retention behavior of ziprasidone and its impurities

ABSTRACT

Influence of nine different solvents, either alone or in a mixture, on the retention behavior of ziprasidone and its five impurities were examined by normal-phase thin-layer chromatography. Migration distances of the examined compounds obtained under the examined chromatographic conditions were correlated with calculated mobile phase properties, such as Snyder polarity and Hansen solubility. Linear or second-order polynomial relationships with high correlation coefficients were established between investigated variables. The obtained mathematical functions and statistical results indicated that selected mobile phase properties can be used for the prediction of the retention behavior of ziprasidone and its five impurities.     

Comparison of Optimization Based on Information Theory with Optimization of Rs in Column Chromatography

Abstract

Optimization based on the function of mutual information (FUMI) is reviewed by comparison with optimization of Rs in column chromatography. The following variables are considered: mobile phase composition; pH; column length; the amount of internal standard; detection wavelength. FUMI is equivalent to the precision of measurements and takes a maximum at the optimal condition. However, Rs neither takes a maximum nor corresponds to the precision. This paper demonstrates that FUMI is a superior measure of chromatographic performance.     

New Perspectives in Micellar Liquid Chromatography

Abstract

This paper will summarize several new findings obtained in our laboratory on the use of micellar mobile phases in liquid chromatography. The topics to be addressed include (i) stationary phase modification by the mobile phase surfactant in micellar liquid chromatography, (ii) investigation of the retention mechanism in micellar liquid chromatography (MLC) using an alkyl-benzene homologous series, (iii) evaluation of the effects of organic additives upon retention and efficiency in MLC, and (iv) preliminary characterization of several new classes of surfactant molecules for use in MLC. The information gained from these studies provides new insights into the dynamics of MLC and demonstrates their potential usefulness in several new separation applications including the resolution of optical isomers.     

Microcolumn Liquid Chromatography Combined with Computer-Assisted Retention Prediction System for Polycyclic Aromatic Hydrocarbons in Extract from Diesel Particulate Matter

Abstract

Recent advances in column and instrument technology have made the development of d new generation of high-resolution microcolumn liquid chromatography possible. In addition to offering reduced solvent consumption, this chromatographic technique also yields higher mass sensitivities than those in conventional systems. In this study, the applicability of this technique to the analysis of polycyclic aromatic hydrocarbons (PAH) is investigated. PAH in the extract from diesel particulate matter were analyzed to demonstrate the utility of this approach combined with the computer-assisted retention prediction. The technique proposed in this study makes very clean and high cost-performance environmental analysis possible.     

Prediction of Programmed-temperature Retention Values of Naphthas by Artificial Neural Networks

Abstract

It is proposed for the first time a method of prediction of the programmed-temperature retention times of components of naphthas in capillary gas chromatography using artificial neural networks. People are used to predict the programmed-temperature retention time using many formulas such as the integral formula, which requires that four parameters must be determined by calculation or experiments. However the results obtained by the formula are not so good to meet the demand of industry. In order to predict retention time accurately and conveniently, artificial neural networks using five-fold cross-validation and leave-20%-out methods have been applied. Only two parameters: density and isothermal retention index were used as input vectors. The average RMS error for predicted values of five different networks was 0.18, whereas the RMS error of predictions by the integral formula was 0.69. Obviously, the predictions by neural networks were much better than predictions by the formula, and neural networks need fewer parameters than the formula. So neural networks can successfully and conveniently solve the problem of predictions of programmed-temperature retention times, and provide useful data for analysis of naphthas in petrochemical industry.     

Molecular Theory of Liquid Adsorption Chromatography

Abstract

A statistical-mechanical theory, based on a lattice model, has been developed to address the molecular mechanism of retention and selectivity in both normal-phase and reversedphase liquid adsorption chromatography. The model is a natural “competitive-equilibrium” one, where possible contributions from solvent-solvent and solute-solvent interactions, and, hence, from solution nonideality, are not neglected. Homogeneous and heterogeneous adsorbent surfaces, single-solvent and binary mixed-solvent mobile phases, and solute molecules of different size and shape are treated. Practical applications of the theory are presented to demonstrate its utility and significance.

For homogeneous adsorbents and neat solvents, the molecular energetics of retention and selectivity are examined, with special emphasis on the effects of solute size and shape, and, relatedly, the modes of solute adsorption. Separations of geometrical isomers and homologous series in real and simulated chromatographic processes are investigated, confirming predictions of the theory and the important role of solvent-solvent and solute-solvent interactions in reversed-phase systems. The implications of a more general retention equation for microscopically heterogeneous adsorbents are discussed. The dependence of capacity ratio on mobile-phase composition for binary solvents is analyzed in some detail. An often important contribution arising from solution nonideality is predicted theoretically. This is shown to be consistent with experimental results on normal-phase and reversed-phase systems.     

Chromatography of Suspensions,An Absolute Particle Size Detector Based on Turbidity-spectra Analysis - a Simulation Study

Abstract

In the chromatography of particle suspensions the use of a variable wavelength spectrophotometer can provide turbidity spectra continuously with retention volume. As suggested by Hamielec [1] this device could form the basis for an absolute particle size detector provided the size distribution in the detector cell could be represented by a known distribution function. In this work it is shown that the two parameter log-normal distribution function is an adequate representation of the detector cell contents. Further a computational scheme is outlined whereby the distribution parameters and the number of particles in the detector cell are calculated as a function of retention volume. It is then possible to obtain size distribution information of the original suspension.     

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.     

Use of Principal Component and Cluster Analysis for the Comparison of Reversed-Phase HPLC Columns

Abstract

The retention of ethoxylated nonylhylphenyl surfactants was determined in reversed-phase high-performance liquid chromatography (RP-HPLC) using various supports (C1, C2, C6, C8, C18, polyethylene-coated silica, and polyethylene-coated alumina). The retention data matrix was evaluated both by principal component analysis and cluster analysis. The retention characteristics of both polyethylene-coated supports were similar to that of C1, the retention capacity of RP columns for surfactants increased with the increasing length of the covalently bonded hydrocarbon chain. The retention of ethoxylated surfactants depended nonlinearly on the length of ehtyleneoxide chain suggesting that the polar ethyleneoxide chains are in folded state under the chromatographic separation.     

Development of Crude Drug Analysis by Liquid Chromatography,and UV and MS Spectrometers

Abstract

The retention indeces of 42 standard compounds in naturally occurring drugs were studied in reversed-phase liquid chromatography. The effluent was monitores by a photodiode array detector and mass spectrometer. The spectra and the retention indeces were used for qualitative analysis of the crude extract components.     

Analysis of Organic Nitrogen Compounds Using Paired Ion Chromatography. Applications to the Analysis of Coal-Derived Liquids

Abstract

Evaluation of HPLC as a possible method by which the nitrogen compounds in coal-derived liquids could be analyzed has met with mixed results. Some chromatography fractions display very different HPLC traces in methanol compared with those obtained in a MeOH-HOAc-PIC mixture, but others are insensitive to the change in eluent. HPLC of several model compounds has revealed basic nitrogen compounds generally have longer retention times in paired ion chromatography (PIC) solutions, but that some actually have shorter times. Heterocyclic nitrogen compounds all give longer retention times in PIC solution than in methanol.     

Reversed-Phase High Performance Liquid Chromatography of Carbon Dioxide

Abstract

An investigation of the qualitative aspects of the liquid chromatography of carbon dioxide is described. It is demonstrated that although injected as a high pressure liquid, carbon dioxide dissolves in aqueous methanol mobile phases and elutes as a solution. The detector response is discussed in terms of the possible chemical interactions between the carbon dioxide molecule and the mobile phase; the effect of eluent pH upon the response is described. The variation of relative retention with mobile phase composition is detailed and the results discussed in terms of Horvath's solvophobic theory.     

Rapid and Complete Separation of Inorganic Polyphosphates from Monomer to 35-Mer by Hplc

Abstract

The on-line coupling system of high-performance liquid chromatography (HPLC) and flow injection analysis (FIA) was developed for the rapid separation and sensitive detection of inorganic polyphosphates. Effects of gradient elution conditions on the chromatographic behavior were studied. The column temperature as well as a chloride concentration gradient were found to be very effective for the improvement of resolution(1). To minimize analysis time and to maximize resolution, the gradient elution conditions were optimized by use of a computer-assisted retention prediction system(2). More than 35 kinds of inorganic polyphosphates could be separated completely within 200 min under the optimum conditions as shown in Fig. 1.     

Abnormal Retention of Some Dihydrogenophosphate-1-benzoylisoquinoline Ions Pairs Exceptionally Stable Observed in Liquid Chromatography

Abstract

Abnormal retention of some dihydrogenophosphate-1-benzoylisoquinoleine ions pairs is described and provided by four experiments : liquid chromatography of papaverine and papaveraldine, dihydrogenophosphate determination with papaveraldine as IIR., liquid chromatography of PV₂ and benzoyl-PV₂ and 4-hydroxy-6 demethyl papaveraidine chromatography. An hypothetic structure of ion-pair is proposed.     

The Effect of Amine Modifiers on the Chromatographic Behavior of Salbutamol on Reversed Phase Chemically Bonded Silica Gel

Abstract

The reversed phase chromatography of salbutamol in an aqueous phosphate buffer with quaternary and tertiary amine modifiers is described. The object was to control the retention and improve the asymmetry for use with electrochemical detection.     

HPLC Retention Index Scale for Nitrogen-Bridged Compounds

Abstract

Retention indices of some nitrogen-bridged compounds having pharmacological activity have been determined. A retention index scale based on the relative retention of a homologous series of C₃-C₂₃ 2-keto alkanes has been worked out. Linear relationships were found between RI and logP, allowing a prediction of retention indices.

The relationships between the structures and the retention indices of these compounds have been interpreted.     

Separation of Sulphonium Salts by Ion Chromatography: Five- and Six-Membered Cyclic Sulphonium Salts

Abstract

Several cyclic 5-and 6-membered sulphonium compounds were separated by ion pair chromatography on a opti-dbb ion pair column. The salts show specific retention behavior when using different mixtures of acetonitrile and aqueous sodium perchlorate solutions as eluents. The increase of retention times with extending chain length of the alkyl group R and with ring size is due to an increase of the solute molecular surface areas which were also calculated. The obtained retention parameters give additional information for structural determination.     

Chemical Modification of Silica Gels After Preliminary Thermal Treatment

Abstract

Chemically bonded phases have been prepared using thermally treated silicagels as basic material. Four bonding reactions with trimethylchlorosilane (TMCS) were successively performed on each silicagel in order to obtain the maximum coverage.

The effect of the chemical modification on the surface structure of packings and on their retention behaviour in reversed-phase chromatography was investigated. The maximum coverage with trimethylsiloxy groups was observed with silicagels previously treated at 300–400°C while the minimum concentration of hydroxyl groups was calculated for silicagels previously treated at 600°C.

Significant differences in retention were observed for these phases in reversed-phase chromatography. Silicagels with maximum coverage were found to be the most convenient for the analysis of apolar solutes while silicagels with minimum hydroxyl group concentration were the most convenient for the analysis of polar solutes.