ANYL 369 |
| Symmetric peak shapes and resolution comparable to analytical LC can be achieved while loading the column with higher mass injections (routinely 100mg). This is done by optimizing the injection process as a separate sub-system using the “at-column dilution” approach to sample injection. Success at injection allows one to then focus attention on the separation to achieve high speed while maintaining high resolution. The key principle is addressing the capacity issues while simultaneously applying techniques to achieve both high speed and separation efficiency. These techniques are the same ones used at analytical scale, namely volume reduction and small stationary phase particles. The capacity issues are most readily addressed by creating a separate sub-system for on-line buffer mixing and by controlling the rate of adsorption of compounds on stationary phase by heating the system. Application of the above concepts allows routine, sustained purification rates of 1g/hr or >200 samples per day per LC/MS operating at 4mm/s (100mL/min) delivering Gaussian peaks with widths as low as 3 s wide. Purities >95% are achieved with >99.9% success rate even for reaction mixtures where the target compound is 5% of the injected sample. This is achieved in a 6 minute cycle time in full gradient mode for k'=20 separations even when operating at 2pH units on the ionized side of the target compound's pKa. Use of gradient regeneration has been found to extend column lifetime to >3000 injections. Further enhancement results from other automation features including mass estimation by ELSD, ultra pure water delivery plumbed to the point source, waste detection, immediate site-wide access to data, and waste destination switching. The impact of these benefits being delivered by a purification expert is a 10 fold improvement in human efficiency relative to medicinal chemists doing the purifications on their own. |
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Fast Preparative Chromatography in Pharmaceutical Drug Discovery
1:30 PM-4:50 PM, Tuesday, August 21, 2007 BCEC -- 105, Oral
Division of Analytical Chemistry |