Chiral e-Times 2009 Volume 1

sign up to receive the Chiral e-Times

Developing a new chiral method typically involves perusing application databases, consulting the literature, screening columns or contracting with a chiral service lab. Supelco can help with all of these approaches.

Centralized location of chiral products, resources, services – via the new Chiral Chromatography portal
Visit www.sigmaaldrich.com/chiral-chromatography

“Chiral Chromatography” has been added to the left navigation bar for quick access to this page from any web topic under Analytical/Chromatography.

(Click image for a larger view)

Chiral Chromatography web resources -
Various technical resources are linked under the Learning Center, including:

• Applications – over 300 enantiomer separations now available in the online catalog
• Bibliography – over 600 citations organized by phase and by analyte class
• Technical literature, handbooks and presentations – available for direct viewing or download

Applications: You can find chiral applications on our site in two ways:

1. Follow the Chiral Applications link under the Learning Center of the Chiral Chromatography portal to the related applications section in the online catalog, where you will find all our chiral applications grouped by compound class.
2. Simply type in the name of the compound in the Search box, located at the top right on every page within our web site. If we have run the separation, it will appear within the “Analytical Applications” tab of the search results

Bibliography: A useful tool to find a chiral separation or a starting point from published methods, our chiral bibliography is accessed through the Learning Center of the Chiral Chromatography portal. Here we have compiled over 600 citations of our chiral HPLC and GC columns published in refereed journals. The references are organized by phase and by analyte class. There are also purely mechanistic papers, and papers published by Professor Daniel Armstrong, the inventor of Astec CYCLOBOND and CHIROBIOTIC phases. The bibliography will be updated semiannually, with the most recent publications in a so-named section.

To find your compound, subject, author, etc. of interest in the bibliography, go to the appropriate compound class and use your browser’s search feature (Ctrl+F, for example).

Technical literature, handbooks and presentations: Through the Learning Center, access technical literature and other documents to help you choose and use a chiral column.
Presentations include recent posters and talks given at tradeshow events like EAS-2008 and Pittcon-2009.

A unique feature of Astec CHIROBIOTIC CSPs is the presence of ionic interactions between the CSP and the analyte enantiomers. Besides having significant contribution to the chiral selectivity and retention, these ionic interactions permit the use of mobile phases that are suitable for LC-MS because they comprise high percentages of methanol or acetonitrile with low concentrations (1 to 15 mM) of volatile acids and bases, or salts such as ammonium acetate or ammonium formate. These mobile phase systems often yield more efficient analyte ionization and correspondingly improved LC-MS sensitivity as well as increased peak efficiencies. When combined with short columns with narrow I.D., CHIROBIOTIC separations are highly suitable for fast clinical and other chiral LC-MS applications.
For more information, view App Note 186, Astec CHIROBIOTIC CSPs for Fast Chiral LC-MS Analysis (303kb PDF).

The enantioselectivity of cyclodextrin-based CSPs is derived from a steric inclusion/exclusion mechanism conferred by the cyclodextrin (CD) cavity, and various chemical interactions with functional groups around the opening of the cavity. Of the five CD derivatives we offer for chiral HPLC, one of the most powerful is the DNP, which comprises a dinitrophenyl functionality on the CD and is bonded through an ether linkage to the hydroxyl groups of the CD. In this arrangement, a pi-electron sharing system is established with analytes having pi-electron systems (e.g. aromatic rings, carbonyl) in the stereogenic environment. The pi-acidity of this group is further enhanced with the introduction of the trifluoromethyl group into the phenyl ring. Although it can be used in reversed-phase, polar organic and normal phase mobile phases, we have found most success under reversed-phase conditions. A benefit of the reversed-phase system is that buffers can be employed to control retention and/or resolution of charged analytes.

An example of the different enantioselectivity for aromatic compounds conferred by the DNP groups is demonstrated in the separation of binaphthol (click for details). View the DNP and our other CYCLOBOND phases. Also, please see the Special Offers section for a limited-time promotion on CYCLOBOND I 2000 DNP columns.

Our Chiral Services laboratory provides column screening, method optimization and purification services for our customers. A differentiating capability we have recently added is the ability to analyze samples in a rapid screening protocol that features an automated LC-MS technique and short, fast column dimensions. Not only is this a differentiating feature of our laboratory, MS-compatibility is also a distinctive feature and fundamental benefit of our chiral HPLC columns: many separations on Astec CHIROBIOTIC and CYCLOBOND CSPs are run in methanol containing volatile salts.

You can view an example of our LC-MS screening protocol.

Recent PittCon and EAS presentations

View all our chiral presentations, including those from PittCon-2009 and EAS-2008, using the Presentations link under the Learning Center of our chiral chromatography portal.

Chirality 2009 (July 12 - 15, 2009, Breckenridge, CO)

At this tradeshow, Supelco will offer three presentations:
"Significant Improvements in Chiral Method Development using an LC-MS-Based Screening Approach"
"Performance and benefits of macrocyclic glycopeptide-based CSPs in enantiomeric purification using bench-top simulated moving bed (SMB) technology"
"Effects of pi-base/pi-acid derivative chemistry on enantioselectivity of chiral stationary phases"

And one vendor seminar:
“Strategies for Chiral HPLC Method Development”

If you are interested in registering for the vendor seminar, please send an email to tracy.ascah@sial.com

To see our complete tradeshow schedule for 2009, visit www.sigmaaldrich.com/analytical-events

Resolution of polar and ionic enantiomers is a unique and valuable feature of Astec CHIROBIOTIC CSPs. The mobile phases for these separations are quite simple: polar organic solvents, such as methanol or acetonitrile, containing volatile acids and bases or their corresponding salts. The concentrations of the acid and base or the acid:base ratio are varied to optimize retention and selectivity.

However, retention time variation and slow equilibration may occur when these additives are employed at high concentrations or when the solubility of the additive in the solvent is limited. We have found that the addition of a small amount of water to the mobile phase increases the additive’s solubility, reduces equilibration time and improves the stability of retention times if needed. Typically, the addition of 5 to 10% v/v water to the methanol mobile phase was sufficient to provide stable retention and maintain enantioselectivity, while also maintaining the same ionic mechanism.

For a limited time --
30% off Astec CYCLOBOND I 2000 DNP

If you routinely screen chiral HPLC columns, or if your enantiomers possess pi-electron systems, then Astec CYCLOBOND I 2000 DNP should be in your toolkit.
This ß-cyclodextrin derivative has unique enantioselectivity toward compounds have pi-electron systems (e.g. aromatic rings, carbonyl groups) in the stereogenic environment. It also has the benefit of operating in familiar reversed-phase mobile phases.

Specify Promotion Code 960 to receive a 30% discount on any CYCLOBOND column listed above.
Offer good through June 30, 2009.