Seminars

Seminars for the The Mass Spectrometry Interest Group of the NCI at Frederick will generally be scheduled for the 2nd Tuesday of each month for 2009. A seminar is usually a 45-50 minute presentation on a topic of general interest followed by open discussion.

Meetings

Separate from the seminars, there will also be smaller meetings which will consist of a 20-30 minute presentation on a topic of specific interest followed by open discussion. Meetings will not have a regular schedule.

Seminar

Speaker: Donna Zwirner, Waters, Milford, MA 01757

Topic: "A Systematic Approach to Reducing Matrix Effects in LC/MS/MS Analyses"

Place: Building 549, Conference Room A, NCI at Frederick, Frederick, MD - Need Directions?

Time: Tuesday, January 20, 2009, at 2:00 PM

Abstract: The MS response obtained from an analyte in neat solution can differ significantly from that same analyte in a matrix. Matrix effects, resulting from co-eluting matrix components that compete form ionization capacity, manifest themselves as suppression or enhancement of the analyte signal. Matrix effects can be infinitely variable and difficult to control or predict. They are caused by numerous factors, including but not limited to, endogenous phospholipids. Other sources of variability in matrix effects include subject differences, possibly due to diet or other factors, and concentration of the endogenous phospholipids. The severity and nature (suppression versus enhancement) of matrix effects observed can be a function of the concentration of the lipids at the elution time of the analyte. Matrix effects can also be compounded by co-eluting metabolites, impurities or degradation products. All of the above can cause significant errors in the accuracy and precision of bioanalytical methods. These effects should be evaluated as a part of quantitative LC-ESI-MS/MS method development, validation, and routine use. We believe that all available tools, or combinations of tools, should be employed to reduce these effects. In this seminar, we compare different sample preparation methods, investigate the influence of mobile phase pH on both matrix components and several basic analytes, and we compare HPLC and UPLC™ analysis for sensitivity and the presence of matrix effects. We chose to focus on basic analytes in a pharmaceutical bio-analysis environment for this research. The amount of specific matrix components, or classes of matrix components, remaining in the extracts was measured by LC/MS/MS (electrospray ionization) using multiple reaction monitoring (MRM). Upon high energy in-source CID, the lipids implicated in matrix effects yield a characteristic fragment ion at m/z 184, corresponding to the trimethylammonium-ethyl phosphate cation. It is this ion that allows us to monitor multiple phospholipids and lysophospholipids with a single MRM transition, thus maximizing the duty cycle in the mass spectrometer. The relative levels of phospholipids present in our samples were measured by monitoring the transition 184.3 -> 184.3. The cone voltage was set to 90 V and the collision energy set to 3 eV so that no further fragmentation of the diagnostic ion would occur. Based on our research, we conclude that mixed-mode solid phase extraction (SPE), appropriate mobile phase pH and UPLC offer the best solution for controlling matrix effects in bioanalytical analyses.

Arie Hawkins, University of Maryland, Baltimore County, Baltimore, MD 21250
"Structural determination of regulatory domains present in retroviral RNA using FT-ICRMS"
April 22, 2008

Alexander Lazarev, Pressure BioSciences, Inc., Woburn, MA 01801
"Life Under Pressure: Applications of High Hydrostatic Pressure in Life Sciences"
June 10, 2008

Members of the Mass Spectrometry Interest Group (MSIG)
"Highlights of the 56th Annual Conference of the American Society for Mass Spectrometry (ASMS)"
June 24, 2008

Fenhong Song, Agricultural Research Service, USDA, Beltsville, MD 20705
"A Study of Non-Covalent Protein-Protein Complexes under Native Conditions by MALDI"
October 7, 2008

Faith Hays, Shimadzu Scientific Instruments, Inc., Columbia, MD 21048
"Rapid, Reliable Identification of Microorganisms"
November 4, 2008

Peter Nemes, Department of Chemistry, George Washington University, Washington, D.C. 20052
"Direct Analysis and Molecular Imaging of Live Tissues and Single Cells by Infrared Laser Ablation Electrospray Ionization Mass Spectrometry"
December 2, 2008

Donna Zwirner, Waters, Milford, MA 01757
"A Systematic Approach to Reducing Matrix Effects in LC/MS/MS Analyses"
January 20, 2009

Speaker: Alfred Yergey, NICHD, National Institutes of Health, Bethesda, MD 20892
Topic: To be announced