December 2006 Meeting

Ultra High-Pressure LC and Chaotropic Mobile Phase Additives:
A Synergistic Approach to Methods Development

The December 2006 CSSC meeting will be held at the Yankee Silversmith Inn in Wallingford, CT.  The meeting will feature a technical presentation by Dr. Anton Jerkovich of the Novartis Pharmaceuticals, as well as hors d'oeuvres and a cash bar.  The cost of the meeting is $25 ($15 Students and Emeritus) and is to be paid at the event.

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Abstract:  The Waters Acquity Ultra Performance LC (UPLC™) utilizes columns packed with sub 2 um stationary phase particles and allows for pressures up to 15,000 psi to yield increased resolution, speed, and sensitivity versus conventional HPLC. Also, the reduction of time, solvent, waste disposal and resources makes it a very attractive new technology allowing for fast HPLC method development and enhanced sample analysis during preformulation screening. The use of the Acquity for pH scouting experiments and the determination of the analyte pKa has been demonstrated to be an effective tool in aiding the chromatographer during the method development process.

The fundamental characteristics of this promising new technology were evaluated for the analysis of small molecule and peptide drug product formulations. The use of longer columns for the more challenging peptide separations has also led to an enhancement of the efficiency and resolution between critical pairs. Also, the use of chaotropic agents for the enhancement of the separation selectivity of basic compounds and peptides was demonstrated.

The separation of protonated basic pharmaceutical compounds may be a challenging task due to their early elution, poor peak shapes and limited loading capacity. Occasionally ion-pairing reagents are used for HPLC separation of basic compounds and peptides to enhance their retention and reduce peak tailing. Recently inorganic anions (chaotropic anions) have been used for selective variation of the retention of ionic analytes, improvement of loading capacity and peak symmetry. It has been found that the retention as well as the peak shape of protonated basic analytes is dependent upon the type and concentration of inorganic salt employed.

Employment of chaotropic additives at normal operation pressures (<4000 psi) and at elevated pressures (>9000 psi) for enhancement of basic pharmaceutical compounds and peptides retention and peak symmetry was investigated. The effect of the concentrations of different inorganic mobile phase additives (i.e., KPF6, NaClO4, TFA) were studied. Increased retention and reduction in tailing was observed leading to an enhancement of the analyte sensitivity. Moreover, significant changes in the separation selectivity were observed using perchlorate and hexafluorophosphate additives compared to conventional TFA additive for simple and complex peptide separations. These studies showed that a judicious selection of inorganic additives would allow for control of the retention and separation selectivity of basic compounds and peptides.

Biography:  Dr. Anton Jerkovich -- Novartis Pharmaceuticals

Yankee Silversmith Inn
1033 North Colony Road
Wallingford, CT 06492
(203) 269-5444

Last Updated:  11/26/2006 08:02 PM