Chiral e-Times 2008 Volume 1

1. New corporate chiral web portal
2. Seminars & workshops on chirality at EAS
3. Commissioning of Chiral Services Laboratory
4. Updated and newly released CHIROBIOTIC brochure
5. Tips and Tricks – Improve efficiency of chiral column screening

Sigma-Aldrich is a leader in chiral products and services for chemical synthesis, drug discovery, and analytical assessment. Our regularly-updated Chiral Portal presents all of our products, services and literature for chirality in one convenient location. The site (sigmaaldrich.com/chiral) can be used to access our chiral HPLC and GC columns, and our Chiral Services Laboratory.

Practical Enantiomer Separations – Full-day Course
Dr. Daniel W. Armstrong, University of Texas professor and pioneer in chiral stationary phase development, will present a one-day course entitled “Practical Enantiomeric Separations” at the Eastern Analytical Symposium and Exposition (EAS) on Tuesday, November 18, 2008 from 8:30 AM to 5:00 PM. Please visit the EAS web site (www.eas.org) for complete information and to register for this important training session.

Basic Chiral HPLC Methods Screening and Optimization – Shortcourse
Thomas E. Beesley, founder of Astec, will give a one-hour shortcourse on basic chiral HPLC methods screening and optimization on Tuesday, November 18 from 1 PM – 2 PM in McDivitt Room at the EAS symposium. Sign-up for this and our other Supelco EAS shortcourses at www.sigmaaldrich.com/analytical-events.

An ideal partner for clients in pharmaceutical drug discovery, chemical, agrochemical, food and beverage, flavors and fragrances and other industries, our key services provided by the laboratory include multi-column screening (HPLC and/or GC), method optimization, determination of preparative loading capacity and minimum detection limits, and isolation of mg to gram quantities of purified enantiomer. Larger-scale purification is possible using our SAFC facilities world-wide. Methods can be LC-MS compatible for clinical, stability or dissolution studies.
Laboratory personnel have extensive expertise in both analytical and preparative chiral and achiral separations. They work closely with the client to fully understand the specific requirements of the separation, including final enantiomeric purity and instrument compatibility. State-of-the-art instrumentation includes GC and HPLC with UV, MS, ELSD and optical rotation detection. The client receives a detailed report that includes optimized analytical methodology, summary of column screening experiments, recommendations and any observations made during the method development process. Diligent attention is paid to ensure all aspects of the method and results are kept in strict confidence.
Our Services Laboratory is distinct in offering HPLC column screening in LC/MS-compatible reversed-phase, polar ionic and polar organic separation modes, using CHIROBIOTIC™, CYCLOBOND™, P-CAP™ and other CSPs and modes as dictated by the sample solubility and customer requirements.
For information visit sigma-aldrich.com/chiral_services or send an email to techservice@sial.com

The CHIROBIOTIC family comprises highly enantioselective chiral HPLC stationary phases (CSPs) based on naturally occurring macrocyclic glycopeptides that have been bonded through multiple covalent linkages to high purity silica particles. Developed by Dr. Daniel Armstrong, CHIROBIOTIC CSPs are unique in possessing ionic functional groups, which means they can be used for reversed-phase and LC-MS separation of ionizable enantiomers. The members of the CHIROBIOTIC family have complementary stereoselectivity. If, after optimization, one CHIROBIOTIC CSP does not give baseline resolution, testing the other CHIROBIOTIC CSPs in the same mobile phase typically results in complete resolution.
Features:

• Aqueous and non-aqueous separations on the same column
• Ideal for reversed-phase and LC-MS
• No solvent or additive memory effects
• Robust columns with long lifetimes
• Solvent choices maximize sample solubility
• Excellent preparative scalability and capacity
• Fast kinetics for speed and efficiency

Obtain the new 12-page CHIROBIOTIC brochure by calling (814-359-3441), emailing us (techservice@sial.com), or downloading/viewing it.

CHIROBIOTIC CSPs possess ionic functional groups and are ideal for use in the so-called polar ionic mode, which is defined as polar organic solvents (methanol or acetonitrile) to which are added soluble salts, acids, bases or combinations of these additives. The polar ionic mode is useful for ionizable compounds, where a good starting mobile phase is 0.1% TEA/ 0.1 % acetic acid in methanol. In the case of LC-MS, use volatile ammonium salts, like ammonium formate or ammonium trifluoroacetate.
When working with polar ionic mode, method development and optimization involves adjusting the ratio of acid (typically acetic acid) to base (typically TEA) to adjust selectivity and retention. The ratio depends on the pKa of the enantiomers and other factors. For basic analytes, use higher proportion of acid, while for acid analytes, use higher proportion of base. The acid-base ratio can be from 4:1 to 1:4. A 1:1 ratio is used for screening purposes. If the retention is still too short, using a low concentration of TEAA (0.1%) or replacing the methanol with up to 50% acetonitrile will reduce the mobile phase strength. However, if the compound is neutral and not very polar, there will be little or no retention under polar ionic conditions and a different mobile phase system, like normal phase, should be tried.