Generic gradient method

The fifth major improvement was to use a fast generic gradient method for the analysis of the samples, which usually takes place in an overnight run of. sample vials from 24 compounds. The fast generic HPLC methods have been discussed in Chapter 2. The method applied here was a 3.5 min gradient from 0 to 95% acetonitrile using a Supelcosil-ABZ 30 x 4.6 mm column with a 1.5 ml/min flow rate. Together with the re-equilibration time the cycle time for each sample was 7.5 min. 

In conclusion, the application of a separation technique such as HPLC to the measurement of concentration in the determination of octanol-water partition coefficients greatly enhances the traditional methods. It is possible to automate the measurements and use much smaller amounts of compound without the need for very high purity. With the application of a fast generic gradient method, there is no need for method development and the analysis time can be reduced to 5-7 min per sample. 

Analysis of the Saturated Solution and Residual Solid High performance liquid chromatography (HPLC) is the most commonly used analytical tool for the analysis of saturated solutions. Its advantage over the ultraviolet method is that it can detect impurities and any instability. A generic gradient method can be made readily available that is stability-indicating enough for multiple compound analyses without the need to make major adjustments in the column or mobile phase. 

The phases were tested for polar compound retention by running a gradient method using a set of probe compounds made up of samples and standards that were effectively unretained on the generic LC/MS method. To compare the different stationary phases... 

Fig. 8.14. Chromatograms from the retention probe pair for calibrated method B run on (a) the LC/MS system using the standard generic gradient, and (b) the autoprep system using calibrated method B.

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