28
September 2009
Ketamine Trimipramine
Cellulose-2 (Table 1). Chiral recognition was observed for 63 % of these compounds with 50 % of them being baseline resolved (combined results for Cellulose-1 and -2).
Conclusions • RP chiral LC on polysaccharide-based CSPs employing ammonium bicarbonate or acetate as mobile phase buffer salt is complementary to NP and PO separation modes. Furthermore, RP shows the highest potential for successful chiral LC/MS(MS) methods of analysis.
• Ammonium bicarbonate is the preferred buffer salt with ESI+ MS/MS detection for most basic pharmaceutical stereoisomers. Ammonium acetate is a viable alternative to ammonium bicarbonate but is less successful in providing baseline resolution.
Figure 3: Effects of OrganicModifier on Enantioresolution in RP on Cellulose-2
• Diethylamine (as additional additive) can improve the chiral resolution of strong basic compounds, but it has a negative effect on analyte response in ESI+MS/MS even at low concentration levels (e.g. 0.025 %).
• Decreasing the mobile phase strength in RP (less % CH3CN or MeOH) has the expected effect: it increases retention and also enantioselectivity; adjusting % organic modifier is essential to optimizing chiral resolution.
Trademarks Lux is a trademark of Phenomenex, Inc. TurbolonSpray is a registered trademark of Applied Biosystems. © 2009 Phenomenex, Inc. All rights reserved.
Figure 4: Effects of Buffers on Enantioresolution in RP LC/MS/MS on Cellulose-1
Figure 5: Effects of Additives and Column Temperature on Enantioresolution in RP LC/MS on Cellulose-2
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