ChromSword models

Finally, structure-based predictive software is commercially available (such as CHROMDREAM, CHROMSWORD or ELUEX) for mobile phase optimisation in RPC. This software incorporates some features of the expert system, as it predicts the retention on the basis of the molecular structures of all sample components (which should be known) and the known behaviour of model compounds on various HPLC columns. No initial experimental runs are necessary as the retention data are calculated from the additive contributions of the individual structural elements to the retention, contained in the software databa.se and consequently optimum composition of the mobile phase is suggested. Such predictions are necessarily only approximate, do not take into account stereochemical and intramolecular interaction effects, and predicted separation conditions can be used rather as the recommendation for the initial experimental run in the subsequent optimisation procedure. 

HiPac (53) from Phase Separation is another commercially available software package. In several aspects this software is similar to DryLab, but its most important feature is that it can estimate the optimum mobile-phase conditions for the separation of the mixture at hand or only a selected number of peaks. Recently, ChromSword (commercially available from Merck, Germany) was introduced (34). It uses a retention mc el based on solvophobic theory. The input for this package can be the structural formulas of the solutes, the combination of structural formulas and retention data from a single run, or retention data from two runs. Data from additional runs are incorporated into the model, and prediction accuracy below 3% can be achieved under these circumstances. 

Figure 3.24 ChromSword prediction for a last two peaks come cioser together, as in gradient from 45 to 80% methanol in 25 min the real measurement shown in Figure 3.22. based on the linear model. With one click The input data are those from Tabie 3.4. the quadratic function is selected and the...

Optimal isocratic and/or gradient conditions are predicted by computer optimization software by retention time and peak width modeling, e.g., with DryLab (LC Resources, BASi Northwest Laboratory Services, Walnut Creek, CA, USA), LC Simulator (Advanced Chemistry Development, Toronto, Canada), or ChromSword (VWR International, Darmstadt, Germany). 

ChromSword works with different retention models. The retention model is a type of experiment-based mathematical expression that describes the relationship between the retention of a compound and its properties, as well as the conditions appertaining to the chromatographic experiments. The determination of retention models that adequately describe the effect of chromatographic conditions on the retention of compounds in a sample is very much the focal point in method development software. In this case, on the basis of only a few experiments, the... 

ChromSword supports three approaches for the determinahon of retenhon models in reversed-phase HPLC ... 

ChromSword supports the optimization of separation for polynomial models up to a power of six. Thus, the most complex retention-concentration effects can be described and the separation optimized. AU polynomial models predict the retention of solutes rather precisely in the interpolation region of those concentrations studied. These models are less reliable in the extrapolation region. For example, if experiments were performed with 40% and 50% of organic solvent in a mobile phase, one can expect rather good prediction of retention and separation in the region between these concentrahons and less accuracy in the regions of 30-35% and 50-55%. Extrapolahon to wider hmits very often leads to substantial deviations between predicted and experimental data. 

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