MSACL 2017 US Abstract

Investigation of Peak Shape Degradation and Retention Time Shifts

Breland Smith (Presenter)
University of California San Diego

Bio: BS and MS in chemistry completed at Illinois State University (Normal, IL) specializing in organic chemistry with research in the area of novel porphyrin synthesis. Ph.D. in medicinal chemistry received from the University of Arizona (Tucson, AZ) with research focused on design, synthesis, and evaluation of small molecule drugs against novel translational targets for diseases including Alzheimers neurodegeneration and cancer. Currently a clinical chemistry post doctoral fellow at UCSD in a ComACC accredited program. Recently completed ASCP exam for technologist in chemistry (ASCP, C) and currently ABCC board eligible.

Authorship: Dr. Breland Smith, Dr. Robert Fitzgerald
University of California, San Diego

Short Abstract

LC system pressure is affected by various factors including mobile phase composition, column length and internal diameter, particle composition, temperature, and flow rate which are also modulated to affect peak resolution and retention time. There is often a compromise in optimizing separation efficiency while maintaining proper system pressure. This session will discuss the relationship between these factors, system pressure, and separation as well as demonstrate how a system leak can affect analytical separation by describing a case study that involves LC method failure due to a small, high pressure leak following annual maintenance. In addition, this presentation will give insight into how to investigate and diagnose an unexpected change in separation performance.

Long Abstract

Various factors can affect the separation efficiency of an LC method including mobile phase composition, column length and internal diameter, particle composition, temperature, and flow rate. LC methods for separation of multiple analytes are designed to maximize peak resolution while minimizing run time, which can be done by modulating the various factors listed above. However, these factors also greatly affect LC system pressure and there is often a tradeoff between optimizing separation efficiency and maintaining system pressure within a range that the instrument can manage. Excessively high pressure can lead to leaks in the LC flow which can have drastic effects on peak shape, resolution, and retention time of eluting analytes.

Regular system maintenance including cleaning and replacing solvent lines and connections is extremely important to prevent unexpected hardware failures that can lead to expensive disasters and/or misanalysis of patient samples. Following maintenance procedures it is critical to verify that peak fittings have been sufficiently tightened and proper connections have been made as improper connection replacement is one of the most common causes of system leaks which will often result in rapid and drastic deterioration in peak shape and retention time. System suitability tests should be performed to identify any changes in analyte separation or elution. It is important to know how to diagnose a potential leak as all methods will not necessarily be equally affected. Subtle leaks may not arise until the system reaches a given pressure, thus methods that run at lower pressures may be unaffected and therefore may not be a good measure of overall system suitability. Furthermore, once suspected it is important to know how to locate the site of a leak since small leaks may not be visible to the naked eye. This presentation will describe a case study that involves troubleshooting of an LC method failure due to small, high pressure leak following annual maintenance.

Learning Objectives:

1) Understand the factors that affect LC pressure and separation efficiency.

2) Understand how to properly check and confirm LCMS system suitability following system maintenance.

3) Understand the complexity of an LC flow system and how to diagnose and locate a potential leak in the LC system.

4) Understand how to investigate an unexpected change in peak shape, resolution, and/or retention time of an LC method.


References & Acknowledgements:

Dr. Judy Stone


Financial Disclosure

DescriptionY/NSource
GrantsyesWaters
SalaryyesUCSD, Dept of Pathology
Board MemberyesAACC San Diego Local Section
Stockno
Expensesno

IP Royalty: no

Planning to mention or discuss specific products or technology of the company(ies) listed above:

no