Biomedical Engineering Reference
In-Depth Information
Internal Standards for Quantitative
LC-MS Bioanalysis
Aimin Tan , Nadine Boudreau , and Ann Lévesque
Abstract
Internal standards play critical roles in ensuring the accuracy of reported
concentrations in LC-MS bioanalysis. How do you find an appropriate internal stan-
dard so that analyte losses and experimental variations during sample preparation,
chromatographic separation, and mass spectrometric detection could be corrected?
How is the concentration of an internal standard determined? Should internal standard
responses be monitored during the analysis of incurred samples? What are the main
causes for internal standard response variations? How do they impact the quantita-
tion? Why are stable isotope labeled internal standards preferred? And yet one
should still have an open-mind in their usage for the analysis of incurred samples.
All these questions are addressed in this chapter supported by theoretical considerations
and practical examples.
1
Internal Standards and Analytical Calibrations
Biological samples (plasma, serum, blood, and urine) are very complex. They
contain a wide variety of matrix components such as proteins, lipids, and salts. To
quantify trace amount of analytes (e.g., drug and its metabolites) in complex bio-
logical samples by liquid chromatography-mass spectrometry (LC-MS), the sam-
ples should be properly treated prior to being injected onto an LC-MS instrument,
A. Tan (
*
)
BioPharma Services, Inc ., Toronto , ON , Canada
e-mail: Aimintan@hotmail.com
N. Boudreau • A. Lévesque
PharmaNet Canada, Inc. , Québec , QC , Canada
