33
currents of 140 to180µamps for 50µm I.D. columns.
Temperatures: Capillary and sample storage =22°C.
Sample Introduction: Pressure injection of 4 seconds at 0.3psi.
System Suitability: The instrument was checked daily with test mixtures designed to assess the performance of both the reagents and the instrument. Example runs are shown in Figure 2.
Selection of Racemic Compounds: Racemic compounds were selected for study on the following basis:
Figure 1. Tray location: 2.5 = 25 mM Buffer Cond Sol = Conditioning Solution
1. All drugs were basic drugs and a subset of a large group (692) included in a screen developed by Hudson et al. (3).
2. From the initial group of 692 compounds, a smaller subset of 299 compounds, which had been run in 1.2% ß-Cyclodextrin and 0.5% hydroxypropyl- ß cyclodextrinin pH 2.38 phosphate buffers, was evaluated.
3. Evaluation of the data from these systems and examination of their chemical structures helped to identify which compounds were available as racemates.
4. A final group of 101 racemic compounds was selected for the HSCD study.
Results
1. Each drug or metabolite standard was run multiple times in order to adjust the concentration of the solution and determine the resolution at the appropriate concentration.
Figure 2. System Suitability TestMixtures
2. This was necessary because many of the metabolites were rare compounds and were not available as accurately known quantitative standards.
3. The group of 101 compounds was run in the 5% solution of each HSCD.
4. Results are shown in Table 1 and include the resolution and the corresponding HSCD System.
5. Two examples of HSCD separations of venlafaxine, citalopram and their metabolites in Gamma-HSCD are shown in Figures 3 and 4.
6. Of the 101 compounds, 28 were selected for additional runs at a concentration of 2.5 and 7.5% of each HSCD.
7. Ninety-five (95) of the 101compounds (94%) had a resolution of 2.0 or greater.
8. A resolution of 1.0 or greater was determined using a USP model for 100 of the 101 compounds.
Figure 3. Venlafaxine andMetabolite in 5% Gamma-HSCD
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