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.

Description of the general principles underlying DryLab I/mp.

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.

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.

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.

The method described in this paper was developed with the help of the gradient elution technique. With known dwell volume, gradient elution could be used in routine work without problems. Computer supported HPLC-method development allows the control of a large number of experiments on the screen and verification only of the experimentally promising ones. The method has been developed in 3 days and is approved in practice. With the method, 5 by-products of the synthesis of Atenolol could be identified and quantitatively determined.