ANYL 373 |
| Frequently, candidate compounds in drug discovery and development programs are chiral. Separations for measurement of these compounds are typically done with normal phase LC (NP-LC) or supercritical fluid chromatography (SFC). Mass spectrometry (MS) can dramatically enhance sensitivity and specificity of detection which can be of high value for samples coming from in vitro and in vivo studies. However, only SFC (not NP-LC) can be easily interfaced with a MS. We have coupled analytical-scale SFC with both single-quadrupole (SFC/MS) and triple-quadrupole (SFC/MS/MS) mass spectrometers. We have used this combination to take advantage of the low viscosity in SFC for fast chiral separations simultaneously with the high sensitivity and specificity of MS/MS. Using this combination led us to study a variety of parameters including temperature, MS split ratio, MS makeup flow composition in an effort to optimize the overall sensitivity. After some optimization experiments, we have used SFC/MS and SFC/MS/MS to measure the levels of drug candidates (dosed in racemic mixtures and as individual stereo-isomers) in rat plasma and brains. Baseline separation of racemic mixtures was achieved in a 2-min SFC runs with a LOQs of 250 ng/mL or less for samples prepared with only a 4 to 1 acetonitrile precipitation. All of our results to date indicate that in vivo absorption and delivery of stereo-isomers generally always is stereo-specific, or in other words, dosing the racemic mixture always results in measurably different rates of delivery (some markedly so) for each of the stereo-isomers. |
|
Analytical Approaches
9:00 AM-12:00 PM, Wednesday, August 22, 2007 BCEC -- 104B, Oral
Division of Analytical Chemistry |