Literature | MOLNÁR-INSTITUTE

Journal of Chromatography · 1991

Computer simulation as an aid in method development for gas chromatography: III. Examples of its application

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

The use of computer simulation for developing optimized gas chromatographic (GC) separations is illustrated for several samples. Resolution maps (plots of Rsvs. heating rate r) for different starting temperatures provide a means for the rapid exploration of separation as a function of the temperature program in the case of programmed-temperature GC. Isothermal separations are easily developed by trial and error, because of the speed of computer simulation. More complex samples may require multi-ramp temperature programs; these require a greater method development effort, but partial resolution maps can help facilitate this process.

LC GC · 1990

Reproducibility problems in gradient elution caused by differing equipment

Lloyd R. Snyder, John W. Dolan

When a gradient elution method is transferred from one high performance liquid chromatographic system to another, differences in the equipment may contribute to lack of method reproducibility between the two systems. A primary cause of this problem is the difference in the dwell volume between the two systems. This paper discusses the origin and relative importance of dwell-volume effects in method reproducibility

American Laboratory · 1990

A Method Development System for Liquid Chromatography

J. R. Gant, A. F. Vandemark, A. F. Poile

Use of DryLab programs as the core of a systematic method development strategy

Journal of Chromatographic Science · 1990

Integration of Computer-Aided Method Development Techniques in LC

John W. Dolan, Lloyd R. Snyder

Computer-aided method development techiques have been commercially available for a number of years. Each of these procedures has strengths and weaknesses. In the past, hidden difficulties in the practical application of computeraided method development have discouraged their widespread use. This paper proposes the complementary use of these techniques so that their strengths are maximized while their weaknesses are compensated for. The result is a method development strategy that obtains simple solutions for simple separation problems and reserves the more complex solutions for difficult separations.

Journal of Chromatography · 1990

Use of high-performance liquid chromatography in the pharmaceutical industry

Fritz Erni

Requirements for new pharmaceutical products and their impact on applications of high-performance liquid chromatography (HPLC) are discussed. The strengths and weaknesses of HPLC in this context are evaluated and compared with current trends and expectation in separation science.

American Laboratory · 1990

Liquid Chromatography Expert Systems: A Modular Approach – Solvophobic Interactions Part III

John W. Dolan, Lloyd R. Snyder

Brief review of currently available expert system and simulation software approaches

Journal of Chromatography · 1990

High-performance liquid chromatographic computer simulation based on a restricted multi-parameter approach: II. Applications

L. R. Snyder, J. W. Dolan, D. C. Lommen

A computer program (DryLab® MP) is described that allows restricted multi-parameter mapping for any number (or kind) of separation variables, based on only a few experiments. Multi-parameter computer simulation can be used to develop an high-performance liquid chromatographic method from the beginning, or it can be used to enhance a method developed by other means; e.g., by trial-and-error, single-parameter mapping, etc. The software can also be used to evaluate (and improve) method ruggedness. Finally, various problems (column-to-column variability, change of retention with ambient temperature fluctuations, experimental errors, etc.) that are commonly encountered during routine operation can be handled in the same general way. Examples of these various applications are given.

Journal of Chromatography · 1990

High-performance liquid chromatographic computer simulation based on a restricted multi-parameter approach: I. Theory and verification

J. W. Dolan, D. C. Lommen, L. R. Snyder

A computer program (DryLab MP®) is described for the simulation of HPLC separations where two or more variables (e.g., temperature and pH) are changed simultaneously. It is assumed that preliminary method development has resulted in a mobile phase of appropriate strength, such that 1 < k′ < 20 for all bands in the chromatogram. If it is desired to simulate separation as a function of changes in the values of n variables, then one or two additional runs are carried out for each variable —changing only that variable. Retention times for each of the latter runs are entered into the computer, and predictions of separation as a function of all conditions are now possible. Because simultaneous changes in two or more variables can lead to significant interaction effects and less accurate predictions, the software evaluates each simulation for possible errors. Allowed conditions must be capable of predicting values of α with an accuracy better than ± 2% (1 S.D.). The present computer program has a number of possible applications during and following method development, as discussed in the following paper (Part II).

HPLC of Biological Macromolecules: Methods and Application · 1990

Separation of Large Biomolecules by Gradient Elution

Karen M. Gooding, Fred E. Regnier, Lloyd R. Snyder

A review of the use of gradient elution and computer simulation (DryLab G/plus) for the separation of large biomolecules

Analytical Chemistry · 1990

Computer simulation (based on a linear-elution-strength approximation) as an aid for optimizing separations by programmed-temperature gas chromatography

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

If the dependence of retention on temperature is specified for the various components of a sample in isothermal gas chromatography (GC), it is possible to predict retention, bandwidth, and resolution for programmed-temperature GC separations as a function of experimental conditions. The use of a linear-elution-strength (LES) approximation for isothermal retention allows these predictions to be carried out more easily and conveniently, in turn facilitating rapid simulations with a personal computer. This approach to GC method development appears promising, especially if segmented-temperature programs are used. The LES approximation also provides added insight into how different factors affect separation in programmed-temperature GC.

HPLC of Biological Macromolecules: Methods and Application · 1990

The 30S Ribosomal Proteins as a Model for the Optimized Separation of Large Biomolecules by Reversed-Phase HPLC

Karen M. Gooding, Fred E. Regnier, B.F.D. Ghrist, B.S. Cooperman, Lloyd R. Snyder

Application of DryLab G/plus to the separation of the 30S ribosomal proteins

Journal of Chromatography · 1990

Computer Simulation for Optimization of High-Performance Liquid Chromatography of Some Phenolic Pollutants

W. Markowski, T. H. Dzido, E. Soczewiński

Computer simulation was used to optimize high-performance liquid chromatography of phenol and its chloro and nitro derivatives. On the basis of two linear gradient runs of different steepness (RP-18—water + methanol + 1% acetic acid), several simulated gradient runs allowed the optimum gradient programme and flow-rate to be chosen so that the time of analysis could be considerably shortened. Good agreement between simulated and experimental chromatograms was obtained in spite of changes in experimental conditions.

American Laboratory · 1990

Computer-Assisted Optimization of Temperature-Programmed Gas Chromatographic Separations

D.E. Bautz, John W. Dolan

Description of commercial program and application to a complex sample (spearmint oil).

Chromatographia · 1989

High-performance-liquid chromatography of Thermus aquaticus 50S and 30S ribosomal proteins

I. Molnár, R. I. Boysen, V. A. Erdmann

The ribosomal 50S and 30S subunit proteins (r-proteins) ofThermus aquaticus have, for the first time, been characterized by size exclusion chromatography (SEC) and by reversed phase high performance liquid chromatography (RPC). To ensure that the best resolution in the RPC was obtained. the elution conditions, such as gradient time, flow rate, temperature, ionic strength of the eluent and the type of stationary phase were optimized. Correlation between experimentally found retention times and those predicted by DryLab G was better than 0.7% over 30 peaks. Protein fractions from RPC runs were desalted and processed by gel electrophoresis so that the ribosomal proteins could be identified by their position on SDS-polyacrylamide gels. The enhanced speed and quality of separation which has been achieved in this study is expected to bring advantaces in experimental work with ribosomal proteins as well as with other biopolymers. In our case the high resolution technique provides a basis for the preparation of a collection of individual ribosomal protein components for future rRNA-protein interaction studies.