DryLab

As previously described, Eq. 6 contains two constants characteristic of the system and the sample, feo and S, which can be determined by two chromatographic mns differing only in tc. These two values allow to calculate log fe using Eq. 4. However, because there is no empirical solution, values of log few and S have to be computed by iteration. Such procedures are included in several commercially available LC software packages, such as Drylab (Rheodyne, CA, USA), Chromsword (Merck, Darmstadt, Germany), ACD/LC simulator (Advanced Chemical Development, Toronto, Canada) or Osiris (Datalys, Grenoble, Erance). This approach was comprehensively described and successfully applied for accurate log P determination of several solutes with diverse chemical structures [9, 12, 43, 50]. 

DryLab Chromatography Software, http //www.rheodyne.com/products/ chromatography/drylab/index.asp. 

Following selection of the candidate method, the method is optimized for resolution and run time. As discussed previously, this is readily performed using software tools such as DryLab. The approach may... 

Other chromatographic systems snch as DryLab 2000 Pins from LC Resonrces (http //www.lcresources.com) incorporate aspects of method development and validation throngh simnlation software combined with actnal experiments to determine optimal operating conditions. This system is designed to generate efficient method development and method optimization experiments. Resnlts from these experiments can be nsed for the evaluation of robusmess as part of the validation for methods developed using this type of software. 

Many commercial statistical or chromatographic software packages also allow to set up a ruggedness test. This is for instance the case with Statgraphics Plus, Unscrambler II and DryLab for Windows . This list is far from complete. 

H. Jupille, J.W. Dolan, L.R. Snyder. Drylab G plus User s Manual. Lafayette, CA LC resources. 

Optimization of the gradient separation could be expressed in the form of a mathematical algorithm. Usually from a couple of gradient runs of the same analyte mixture, this is sufficient to calculate empirical constants for the equation similar to equation (2-97). These algorithms are implemented in most of the optimization software, such as DryLab , ACDLabs , and ChromSword . 

In Figure 8-18, a mixture of acids and bases was analyzed on three types of columns phenyl, polar embedded, and C18 column. Significant differences in selectivity were obtained. The separation could be further optimized by modifying the gradient slope and employing off-line method development tools such as Drylab for further optimization and resolution of the critical pairs. 

Moreover, once a particular column or columns that have provided the best selectivity are chosen, an automated method optimization may be performed. This would include employment of an integrated HPLC method development system such as AMDS/Drylab such that the gradient slope/temperature... 

The DryLab model utilized in Waters AMDS has additional requirements The number of sample components should not exceed 12 peak area% should be greater than 1%. These requirements are necessary to achieve greater prediction accuracy only. Any discrepancies could be corrected manually in DryLab using the data entry screen by manually entering the retention of the components from the scouting runs (to assign the peaks with a certain number). DryLab has been used for the method development of model drug candidates... 

Manual optimization of the gradient or the use of Drylab, Chromsword, ACD to determine the desired resolution/selectivity... 

Alternatively, the results from the gradient runs for each sample can be inputted into Drylab, ACD, or Chromsword for further optimization (see Sections 8.5.6.11). For the predicted experimental conditions (i.e., gradient slope, temperature, flow rate), if desired selectivity and resolution can be obtained, an experiment can be run for verification. The peak purity for the main analyte (MS and DAD detection) should be checked in the verification run. If the desired selectivity and/or the target analyte are not spectrally homogeneous, go to Step 6, Figure 8-37. 

Drylab for Gradient Optimization. Drylab was used for further optimization of the run time. All the chromatographic results from the four gradients run on the Waters Sunfire C18 were entered into DryLab to... 

Figure 8-48. (Top) Drylab-predicted chromatogram versus (bottom) verification i...

I. Mohiar, Computerized design of separation strategies by reversed-phase liquid chromatography Development of DryLab software, J. Chromatogr. A 965 (2002), 175-194. 

In this chapter the third level of computer-assisted HPLC—the use of expert systems (like Drylab [1], AutoChrom [2], and ChromSword [3]) for effective method development— is discussed. 

Figure 10-1. DryLab software version 3.0 modeling the separation of a mixture of naphthalenes. Resolution of the critical pair (the two peaks that elute closest together) is denoted as a function of time of gradient. Experimental runs are shown as sohd lines on the resolution map selected prediction is a dashed line.

---