Decades of chromatography research done with DryLab®.

Journal of Chromatography B: Biomedical Sciences and Applications · 1993

Computer-assisted optimization of the gas chromatographic separation of equine estrogens

Arya Jayatilaka, Colin F. Poole

The pharmaceutically important conjugated estrogens of the type excreted by pregnant mares were baseline-resolved by gas chromatography (GC) on a SE-30 fused-silica open tubular column after acid hydrolysis and conversion to their tert.-butyldimethylsilyl derivatives. The temperature-programmed conditions were optimized with the aid of DryLab GC software with excellent agreement between the predicted and experimental results. The composition of conjugated estrogens in Premarin tablets is described as an application of the method.

Journal of Chromatography · 1993

Use of computer simulations in the development of gradient and isocratic high-performance liquid chromatography methods for analysis of drug compounds and synthetic intermediates

Loren Wrisley

DryLab G/plus and DryLab I/plus (LC Resources) are shown to be effective aids in the development and optimization of gradient and isocratic HPLC conditions for the assay of drug substances and related compounds. Data obtained after two experimental runs in the laboratory are entered into the appropriate program where HPLC conditions can be altered (e.g. flow-rate, column dimensions, mobile phase composition, gradient steepness and shape, etc.) to arrive at optimum separation conditions with less analyst time required. The computer simulations from DryLab G/plus are shown to be suitably accurate under “real life” conditions in the development of gradient purity methods for two drug substances (Zalospirone and WY-47 384) and two synthetic intermediates (cyclooctatetraene and 2-methylcarboxybenzaldehyde). Moreover, DryLab I/plus was shown to be accurate in predicting isocratic retention for the separation of impurities in cyclooctatetraene, both in scaling down to small columns for speed and scaling up to a semi-preparative separation for isolation of impurities.

Journal of Chromatography · 1992

Application of the gradient elution technique: Demonstration with a special test mixture and the DryLab G/plus method development software

R. Däppen, I. Molnár

A mixture of ten compounds with an overlapping peak pair was analysed with a 90-min elution gradient. To improve the separation, two reversed-phase gradients differing by a factor of 3 in their run times, were applied. Contrary to expectation, two peak pairs were less well separated in the gradient run with the lower slope. The relative resolution map provided a rapid solution to the problem: a gradient with 16-min run time gave the best separation of the mixture. The simulated chromatogram was verified experimentally. The differences between the predicted and experimental retention times averaged 0.03 min. Further improvement was obtained using a segmented gradient, which adequately separately all peaks in only 9 min.

Journal of Chromatographic Science · 1992

Computer-Assisted Enhancement of Gas Chromatographic Principles for the Teaching Laboratory. Prediction of Retention Data and Chromatographic Separation*

Robert L. Grob, Eugene F. Barry, Sittichai Leepipatpiboon, Jackson M. Ombaba, Luis A. Colon

Computer simulation depicting column temperature—solute retention relationships in gas chromatography is a potentially effective instructional tool and can reinforce theoretical concepts presented in the classroom. The role of computer simulation of gas chromatographic separations in an academic laboratory is described for simple mixtures of alcohols and hydrocarbons for which retention data and chromatograms are accurately predicted. The technique is also illustrated for a more complex sample, peppermint oil, where computer-generated chromatographic data compare favorably with the corresponding experimental data. The approach can be incorporated into presently conducted experiments in the analytical or organic chemistry laboratory and is applicable for both isothermal and temperature-programmed separations.

American Laboratory · 1992

Multiparameter computer simulation for HPLC method development

J. Dolan, J. Lewis, W. Raddatz, L. R. Snyder

Semantic Scholar extracted view of "MULTIPARAMETER COMPUTER SIMULATION FOR HPLC METHOD DEVELOPMENT" by J. Dolan et al.

Journal of Chromatography · 1992

Optimization of the separation of the Rp and Sp diastereomers of phosphate-methylated DNA and RNA dinucleotides

A. J. J. M. Coenen, L. H. G. Henckens, Y. Mengerink, Sj. van der Wal, P. J. L. M. Quaedflieg, L. H. Koole, E. M. Meijer

The separation by reversed-phase high-performance liquid chromatography of Rp and Sp diastereomers of phosphate-methylated DNA and RNA dinucleotides was studied with respect to pH, organic modifier type and concentration and reversed-phase packing material. Drylab G was used to deduce optimum conditions. On the basis of the observed discrepancies between the computer predictions and experimental results, the gradient operation procedure with volatile buffers was improved. By repetitive chromatography on a 250 × 22 mm I.D. reversed-phase column, fourteen diastereomeric pairs were obtained in at least 97% purity and 60% yield, in amounts of 10–100 mg.

Journal of Chromatography · 1992

Computer simulation as a tool for the rapid optimization of the high-performance liquid chromatographic separation of a tryptic digest of human growth hormone

R. C. Chloupek, W. S. Hancock, L. R. Snyder

Computer simulation was used to optimize the separation of a tryptic digest of recombinant human growth hormone using reversed-phase high-performance liquid chromatography in a gradient mode. DryLab G/plus software modelled the retention behavior of the complex tryptic digest mixture as a function of gradient conditions, based on data from two experimental gradient runs. The theoretical optimum separation conditions were rapidly obtained and reproduced experimentally. Resolution did not simply increase as gradient steepness was decreased, rather, an intermediate gradient time provided maximum sample resolution. The simulation results also indicate that the method is reasonably rugged, with little change in the separation expected for different high-performance liquid chromatography systems, and changes in the separation can be compensated by a change in the gradient steepness. Computer simulation can also be useful to quickly reoptimize conditions for a new column, if it fails to provide the same separation.

PZ (Pharmazeutische Zeitung) Wissenschaft · 1992

Determination of by products in atenolol

H. Hofmann, Imre Molnár

The method described in this paper was developed with the help of the gradient elution technique. With known dwell volume, gradient elution could b...

Journal of Chromatography · 1991

Computer simulation of isocratic retentions of alkylketones using gradient data

James D. Stuart, Diana D. Lisi

The use of computer simulation software for high-performance liquid chromatographic (HPLC) method development is considered. In particular, gradient elution data entered into DryLab G/plus are used to predict isocratic retention times. The motivation was to establish whether data generated in a research-grade, gradient environment might be used to simulate accurately isocratic HPLC conditions applicable to a process monitoring operation. Good agreement between experimentally obtained and computer-predicted retention times for a homologous series of alkylketones was found for the conversion from gradient to isocratic elution conditions.

Journal of Chromatography · 1991

Computer-aided optimization of high-performance liquid chromatographic analysis of flavonoids from some species of the genus Althaea

T. H. Dzido, E. Soczewiński, J. Gudej

DryLab G software was used for the optimization of gradient elution programs in reversed-phase high-performance liquid chromatography applied to the chromatographic analysis of flavonoids present in marsh-mallow (Althaea officinalis). The optimization experiments were carried out for a mixture of eight standard solutes (isolated previously from the plant) and then applied to an extract from the flowers of marsh-mallow. Computer simulation experiments allowed convenient analytical conditions to be chosen. The use of two modifiers, methanol and acetonitrile, made the identification of separated components more certain. Good agreement between simulated and experimental chromatograms was obtained.

Journal of Chromatography · 1991

Computer simulation of gradient elution separation: Accuracy of predictions for non-linear gradients

Diana D. Lisi, James D. Stuart, Lloyd R. Snyder

An experimental study was carried out for the separation of a series of homologous 2-ketoalkanes by reversed-phase gradient elution. Both linear and non-linear gradients were used. Computer simulation was applied to these same separations, and comparisons were made between experimental and predicted results (values of retention time, retention time difference and bandwidth). Errors in the predicted separation were generally small and similar for both linear and non-linear gradients. Somewhat larger errors (retention time differences) were found in non-linear gradient separations for bands eluting after a change in gradient steepness. This can be attributed to the dispersion (rounding) of the gradient as it passes through the high-performance liquid chromatographic equipment. Computer simulation was demonstrated to provide predictions that are adequate for the purposes of developing an optimized gradient separation.

LCGC · 1991

Practical applications of computer simulation for gas chromatography method development

G. N Abbay, E. F. Barry, S. Leepipatpiboon, T. Ramstad, M. C. Roman, R. W. Siergiej, Lloyd R. Snyder, W. L. Winniford

Journal of Chromatography · 1991

Computer simulation as an aid in method development for gas chromatography: II. Changes in band spacing as a function of temperature

J. W. Dolan, L. R. Snyder, D. E. Bautz

Several different samples and three stationary phases of varying polarity have been examined for changes in band spacing as a function of temperature. The results of these studies have been expressed as a relative variability in the temperature coefficients of retention (S) for adjacent bands. A theoretical analysis suggests that useful changes in band spacing vs. temperature (or heating rate) can be expected when the difference in S values (ΔS) for two bands is larger than 1 to 2%. The samples studied exhibited variations in average values of ΔS of 0.6–6%. This suggests that optimizing the (isothermal) temperature or (programmed) heating rate of a gas chromatographic separation will often be advantageous.

Journal of Chromatography · 1991

Computer simulation as an aid in method development for gas chromatography: I. The accurate prediction of separation as a function of experimental conditions

D. E. Bautz, J. W. Dolan, L. R. Snyder

Computer-simulation with commercially available software (DryLab GC) allows the prediction of isothermal or temperature-programmed gas chromatographic (GC) separation as a function of experimental conditions. In either case, two experimental runs are carried out initially, using a linear temperature program (heating rate different, all other conditions the same). Data from these two runs are entered into the computer, and separation can then be predicted for other conditions: different temperatures in the case of isothermal runs, or any kind of temperature program for programmed runs. The reliability of resulting predictions was evaluated in the present study for several samples and a wide ranger in separation conditions. Retention time predictions were usually accurate within a few percent, and sample resolution was predicted within about ± 10%. The use of computer simulation should be a considerable help for the rapid development of superior GC methods.

LC GC · 1991

Computer-assisted HPLC method development in a pharmaceutical laboratory

N. G. Mellish

LC GC · 1991

Software for chromatographic method development

A. Drouen, John W. Dolan, Lloyd R. Snyder, A. Poile, J. Schoenmakers

Chromatographic and Membrane Processes in Biotechnology · 1991

Gradient Elution Chromatography

Firoz D. Antia, Csaba Horváth, Carlos A. Costa, Joaquim S. Cabral

Theoretical principles of gradient elution in both linear and nonlinear chromatography are discussed. In analytical applications, where linear chromatography prevails, the theory of gradient linear elution is well developed. On the other hand, in preparative applications,where the high concentrations encountered force the adsorption isotherms into the nonlinear range, gradient elution theory is as yet in its infancy. In this work, the governing principles of the theory, its limitations, and its application in some special cases are outlined.

Journal of Chromatography · 1991

Fast development of a robust high-performance liquid chromatographic method for Ginkgo biloba based on computer simulation

I. Molnár, K. H. Gober, B. Christ

Rapid development of robust and reliable high-performance liquid chromatographic methods for routine quality control of Ginkgo biloba is possible with computer simulation. The goal is to reduce method development time and to increase transparency of the complex composition of plant extracts. With only two basic experiments and a peak tracking process based on the total area ratio compared to the individual peak-area ratios a robust method with more than 50 simulated experiments was completed in 8 h. The best method has been verified experimentally. The correlation between the best simulated run and the final experiment was satisfactory.

Journal of Chromatography · 1991

High-performance liquid chromatography retention index and detection of nitrated polycyclic aromatic hydrocarbons

Tyng-Yun Liu, Albert Robbat

Based on reversed-phase isocratic experiments and gradient optimization modeling, acetonitrile was found to provide optimum separation of nitrated polycyclic aromatic hydrocarbons (nitro-PAHs). A 31-min linear gradient between 24% and 80% acetonitrile in water at 35°C and 0.5 ml/min flow-rate was established. Nitro-PAH retention indices, I, were measured under these conditions. It was found that retention index values varied with changing column temperature and/or mobile phase compositions. Diode-array, fluorescence (FD) and chemiluminescence (CD) detection were studied for nitro-PAHs. Diode-array detection responded linearly with detection limits between 2 and 12 ng/compound injected. In addition, dual-wavelength UV absorbance ratio (A230/A254, A330/A254 and A230/A330) measurements at these wavelength pairs were reported. Fluorescence and chemiluminescence provided increased selectivity and sensitivity. Four orders of magnitude linear range were found for both detection methods with detection limits between 10 and 15 pg and 50 pg (on an NO2/compound mole basis), respectively.

Journal of Chromatography · 1991

Separation and detection of oxidation products in Neurolite raw material

Peta A. Ryan, Barbara A. Ewels, Joseph L. Glajch

N,N′-1,2-Ethylenediylbis-l-cysteine dietyl ester (ECD) is a chiral compound and is a key component of Neurolite, a brain imaging agent. In order for the material to be used in the manufacture of Neurolite, it must meet optical rotation and other purity specifications. The optical rotation of ECD is affected by the presence of oxidation-related impurities of the parent material. Prior to this work, the optical rotation was used as a gross indication of these impurities. During product development, information regarding the impurity profile became necessary in order to understand and monitor ECD degradation. A gradient elution high-performance liquid chromatographic method compatible with liquid chromatography—mass spectrometry was developed and optimized using Drylab G software. System suitability of the method was assessed by adding l-methionine ethyl ester and acetophenone to the ECD standard as resolution markers. Comparison of the resolution between each marker and ECD with previous measures of resolution ensures sufficient zone capacity to resolve all potential impurities.