Optimization Of Mobile Phase Composition Research Articles

Optimization of high-performance liquid chromatographic assay for catecholamines: Determination of optimal mobile phase composition and elimination of species-dependent differences in extraction recovery of 3,4-dihydroxybenzylamine

This paper describes the application of a window diagram technique to optimize the four components of eluent (sodium acetate, sodium heptanesulfonate, acetonitrile and pH adjusted by monochloroacetic acid), for complete separation of five catecholamine compounds and the internal standard (3,4-dihydroxybenzylamine, DHBA). In addition, studies were performed to address the problem of the variable recovery of DHBA from dog plasma due to a time-dependent loss of DHBA. We found that this phenomenon can be prevented by pH adjustment prior to addition of DHBA, allowing development of an accurate high-performance liquid chromatographic assay for plasma catecholamines in dogs.

Simplex optimization of liquid chromatography with the function of mutual information as a criterion

This paper demonstrates that the function of mutual information is a valid objective function for the simplex optimization problems in liquid chromatography. The optimum is indicated by the maximum of the function of mutual information over all the examined conditions. When a new peak which is fused with another peak is discovered by an experiment, the function of mutual information increases substantially to make it easy to approach the optimum. The simplex optimization of mobile phase composition (acetonitrile volume fraction) in reversed-phase liquid chromatography for the determination of a mixture of antipyretics (five analytes) is taken as an example.

Feasible solutions for optimization problems involving unresolved peaks using retention prediction and information theory

This paper treats optimization problems involving unresolved component peaks with the information measure FUMI (Function ofMutualInformation) as a criterion. The LC analysis of 20 PTH-amino acids is taken as an example of the optimization of mobile phase composition, column length and temperature. The quantitative structure-retention relationship is adopted for the simulation and for the establishment of feasible solutions of the problems. The applicability of the FUMI theory is further extended by solving the above optimization problems.

Optimization of mobile phase composition for high-performance liquid chromatographic analysis of eleven priority substituted phenols

The aim of the optimization scheme is to predict the best mobile phase composition consisting of mixtures of water with various proportions of three common organic modifiers, methanol, acetonitrile and tetrahydrofuran

Chromatographic optimization for the determination of traces of selenonium and arsonium cations by HPLC with on-line detection by AAS

Optimal mobile phase compositions were determined for the separation of selenonium ions [trimethylselenonium, (2-hydroxyethyl)dimethylselenonium and (2-acetoxyethyl)dimethylselenonium] and, separately, for arsonium ions (tetramethylarsonium, arsenobetaine, and arsenocholine) by HPLC with detection by atomic absorption spectrometry (AAS). Surface response methodologies were used to predict the variations in detector response (peak area), capacity factors, and selectivities as a function of the mobile phase composition. For selenonium analytes, a mixture of triethylammonium and trimethylsulfonium ions in the methanol-1% acetic acid mobile phase provided a compromise between resolving power and chromatographic efficiency. By contrast, optimum chromatography of the arsonium analytes was obtained by replacing onium additives in the mobile phase by picrylsulfonic acid. For both selenonium and arsonium analytes, the dominant interaction with the stationary phase was with residual silanols and improvements to the chromatographic performance of these analytes resulted in appreciable decreases in their limits of detection.

An optimization procedure for the isocratic high-performance liquid chromatographic separations of environmental pollutants

This paper describes the use of the overlapping resolution mapping procedure to optimize the separation of priority pollutants by isocratic, reversed-phase high-performance liquid chromatography. Three classes of pollutants are considered: polycyclic aromatic hydrocarbons, substituted phenols and phthalate esters. The procedure requires only seven chromatographic runs for each set of pollutants before an optimized mobile phase composition is derived which can satisfactorily resolve all the components in the respective mixtures of pollutants. The main advantage of such a systematic scheme to optimize mobile phase compositions is an improvement in method development times compared to conventional techniques. Another benefit is that expenditures on solvents are reduced.

Determination of Coptis Chinensis Franch and Phellodendron Amurense Rupr in Qingwei-Huanglian Wan by Pls-HPLC Method

Abstract Coptis chinensis Franch contains berberine(1), palmatine(2), jatrorrhizine(3) and etc. And phellodendron amurense Rupr also contains above components. Qingwei-Huanglian Wan is made from Coptis chinensis Franch, phellodendron amurense Rupr and etc. Berberine, palmatine and jatrorrhizine in Qingwei-Huanglian Wan were determined by HPLC. The optimal composition of mobile phase CH3COOEt-HCOOH-EtOH (15:3:2) for HPLC separation of berberine, palmatine and jatrorrhizine was successfully determine by using window diagram technique. Detection wavelength was 345nm. Flow rate: 1.5ml/min. Calibration graphs for (1), (2) and (3) were rectilinear for 0.06–0.39μg, 0.06–0.61μg and 0.01–0.12μg respectively. The basic principle and method of partial least squares method (PLS) is presented in this paper. The data from HPLC were treated with PLS program to obtain the contents of Coptis chinensis corresponding with the requirement. All these indicate that PLS-HPLC method is new and feasible for the determination of c...

Optimization of mobile phase composition for high-performance liquid chromatographic separation by means of the overlapping resolution mapping scheme

The use of the overlapping resolution mapping (ORM) scheme to predict the optimum mobile phase composition for isocratic reversed-phase separation was examined. The application of the method to the separation of a mixture of ten polycyclic aromatic hydrocarbons was demonstrated. The ORM scheme was found to be a rapid and versatile method.

Computer‐assisted optimization of selectivity (mobile phase, pH, and ion concentration) in high‐perfomance liquid chromatography

AbstractA computer‐assisted method is presented for optimization of mobile phase composition in reverse‐phase and normal‐phase HPLC. The method is based on window diagrams, but only three preliminary tests are required. The method is successfully applied to two examples and there is good agreement between predicted and experimental results. Optimal values for ion concentration and pH in ion chromatography from a published optimization method are compared to values calculated using the computer‐assisted method presented in this paper. The same results are obtained, but the method presented here is simpler and faster than previously published one.

Simultaneous Assay of Felbamate plus Carbamazepine, Phenytoin, and Their Metabolites by Liquid Chromatography with Mobile Phase Optimization

Felbamate is an investigational antiepileptic drug (AED) in clinical trials. A high-performance liquid chromatographic method for the simultaneous analysis of felbamate, phenytoin (PHT), 5-(p-hydroxyphenyl)-5-phenylhydantoin, carbamazepine (CBZ), carbamazepine-10,11-epoxide, and carbamazepine-10,11-diol in serum was developed by a mobile phase optimization technique. Capacity factors for the compounds of interest and 12 other AEDs and metabolites were determined with mixtures of methanol, acetonitrile, or tetrahydrofuran and a 0.01 M ammonium phosphate buffer, pH 6.5, on a reversed-phase C8 column. An optimized mobile phase composition was determined that could separate the compounds of interest and three internal standards in less than 15 min. Serum was extracted with CH2Cl2/ethyl acetate (2:1) after addition of three internal standards. The method was validated for within-day and between-day precision and accuracy for the six compounds. Coefficients of variation were generally less than 10% at all concentrations and less than 5% in the typical therapeutic range for each compound. The lower limit of detection was estimated at 0.2 micrograms/ml for CBZ and its metabolites and 0.5 micrograms/ml for felbamate and PHT. For felbamate, the lowest point on the standard curve was 1.88 micrograms/ml with a between-day variability of 10.3%. The assay was used to determine the serum concentrations of PHT and CBZ and its metabolites in a subject before, during, and after felbamate therapy.

Optimization strategies for solutes exhibiting peak tailing : Comparison of two approaches

Two methods have recently been proposed for the improved calculation of resolution values when tailed peaks are present. Both are based on the exponentially modified Gaussian model, but use different approaches. One employs empirical relationships between calculated resolution and area overlap and the other is a mathematical approach in which a new resolution equation is derived. Optimization procedures were developed for both approaches and were compared using computer-generated peaks and actual solute mixtures. Both approaches gave superior mobile phase selection in comparison with the approach in which optimization was performed without consideration of peak tailing. Moreover, the performances of the two methods were almost identical in terms of the mobile phases selected, but slight differences in calculation time and computer memory requirements were noted. It is concluded that both methods may be used succesfully in the optimization of mobile phase composition for solutes giving tailed peaks.

The principle of optimization of binary mobile phase composition of multi-step linear gradient elution

The basic principle of optimal method called “moving overlapping resolution mapping method” to select the optimal binary mobile phase composition of multi-step linear gradient liquid chromatography is discussed with simultaneously considering effects of position of solute inside the column and mobile phase composition on peak resolution and retention value, then a BASIC program based on this principle is developed in IBM-PC computer. The validities of both principle of optimization and BASIC program are confirmed by separation of samples containing bile acids and PAHs in RP-HPLC.

Multivariate calibration strategy for reversed-phase chromatographic systems based on the characterization of stationary-mobile phase combinations with markers

Calibration of chromatographic systems serves several purposes. One of the goals is the correction of retention values in order to make them less dependent on the stationary and mobile phases. Another goal is the transfer of retention values measured on one system to another system. A strategy serving this purpose is reviewed. An example is given which makes use of the latter strategy to correct for batch-to-batch variations of stationary phases. This leaves the way open to update the optimum mobile phase composition. The strategy makes use of special selected compounds: the markers.

Some Physico-Chemical Problems of Prediction of the Optimum Separation in Adsorption TLC with Mixed Mobile Phase

Abstract Determination of optimal composition of a mixed mobile phase used in separation of different substances by adsorption TLC methods is performed usually by the experimental trial and error method. In this paper we have presented and discussed equations permitting to determine the relationships between RM values of the substances and the composition of binary and ternary mobile phases on the basis of measured chromatographic and adsorption parameters and experimentally determined partition coefficients of the substance between the mobile phase components. A good agreement between theoretical and experimental data has been shown. The results of these investigations allow for more precise prediction of the mobile phase optimal composition for the mixture separation.

Design and application of an expert system for mobile phase optimisation in reversed-phase liquid chromatography

The selection of the optimum composition for the mobile phase in reversed-phase high-performance liquid chromatography (HPLC) is a complex task; conventional approaches require the expenditure of significant amounts of time by the analyst, particularly for complex mixtures of solutes of biological origin. Some of the existing strategies for the automated optimisation of mobile phase composition (e.g. Simplex), may fail if the elution order of the components changes; or they may require that standards be chromatographed in order to establish the retention behaviour of each component in a mixture (e.g. resolution mapping). These problems may be overcome if the retention behaviour of each individual solute can be established from the chromatogram of the mixture. In this regard, components can be tracked by exploiting the spectral information generated by a rapid scanning photodiode array detector. Unfortunately this information is often insufficiently detailed to allow an unambiguous model of retention behaviour to be constructed. The system developed by the Authors uses these spectral data as a basis for constructing one or more hypothetical retention models, each of which is refined or rejected as further information is obtained during the progress of the experiment. To improve the reliability of the retention models proposed by the system, the spectral data are utilised in a number of tests designed to assess the purity of each chromatographic peak. The information so generated may be used in conjunction with any previously acquired spectral data both to select an appropriate method for extracting spectra for each component from the matrix of (A, λ, t) data and to establish reliability parameters for the resultant spectra. The development and philosophy of the expert system developed for eluent optimisation in reversed-phase HPLC is discussed.

Separation of isomeric mono-, di- and tributylphenols by high-performance liquid chromatography on octadecyl-silica with methanol-water using alkyl nitrile and alkylamine as surface modifiers

High-performance liquid chromatography with octadecylsilica columns has been used to separate a model mixture of isomeric mono-, di- and tributylphenols. The optimum mobile phase composition was evaluated using the criterion of minimum theoretical plate number necessary for a given resolution of the test components. A dynamic modification of the alkylsilica surface was performed by the adsorption of hexyl nitrile and hexylamine, respectively, added in small concentrations to the eluent. This surface modification results in significant changes in the selectivity of the phase system, and an improved separation of the test compounds can be obtained.

Selection of high-performance liquid chromatographic methods in pharmaceutical analysis : I. Optimization for selectivity in reversed-phase chromatography

The application of solvent optimization to the development of isocratic reversed-phase liquid chromatography has been reported in several publications. Two different approaches to solvent optimization for controlling band spacing for the maximum resolution of samples are “solvent strength” and “solvent type” optimization. To improve the separation selectivity further the combination of these two approaches was examined, as a (global) optimum mobile phase composition requires the optimization of the solvent strength by varying the percentage of organic component and of the solvent selectivity of methanol, acetonitrile, tetrahydrofuran and water. It was found that the combination of “solvent strength” and “solvent type” optimization provides a markedly better separation than either procedure alone.

Sequential simplex optimization and multichannel detection in HPLC: Application to method development

The sequential simplex procedure for the optimisation of mobile phase composition in high-performance liquid chromatography (HPLC) is combined with multichannel detection. The operating software already available in a commercial LC system is exploited and extended to incorporate a number of new routines developed to facilitate HPLC method development. An efficient stop criterion for automated simplex procedures is proposed, based on continuous comparison of the chromatographic response function attained with that predicted. The theoretical basis is developed for a new peak homogeneity test, based on the wavelength sensitivity of the chromatographic peak maximum. An algorithm for assigning peak elution order, based on peak areas at multiple wavelengths, is developed for cases where multiple optima are recorded. The simplicity and practical utility of these techniques are demonstrated in the context of an HPLC separation method developed for a model system of six solutes.

Computer routine for selection of the mobile phase search area in optimisation methods

Computer-based methods for selection of the optimal mobile phase composition in reversed-phase liquid chromatography usually involve selection of a search area of mobile phases formed form linear combinations of isoeluotropic binary mobile phases of water with methanol, acetonitrile or tetrahydrofuran. A simple interactive computer routine is described which facilitates the determination of acetonitrile—water and tetrahydrofuran—water compositions which are isoeluotropic with any given methanol—water binary mobile phase. This routine is based on the assumption that the relationship between ln k′ and the percentage of organic modifier in a binary solvent mixture can be approximated either by a single straight line or a series of line segments. The proposed method is successfully applied to three groups of test solutes (diphenylamines, sympathomimetic amines and aromatic compounds) and it is shown that only minimal experimentation is required to locate isoeluotropic mobile phases for the solutes studied.

Optimization of Mobile Phase Composition in Liquid Chromatography—A Survey of Most Commonly Used Chemometric Procedures

Abstract Chemometrics offers techniques to reduce the number of experiments necessary for obtaining reliable predictions about the optimum conditions for liquid chromatographic separations. This article describes the different chemometric procedures that are currently used for mobile phase optimization. These procedures can be divided in three stages: the selection of the optimization criteria, the choise of the experimental set-up (design) and the evaluation and interpretation of the results. The optimization criteria usually involve resolution (either expressed as α, Rs or P), often analysis time and sometimes column length. The experimental set-up can be either sequential (e.g. simplex algorithm) or simultaneous (e.g. factorial designs). Data can be evaluated either graphically or by mathematical methods. The applicability of the different methods in general and for specific problems is discussed, using examples from the literature.